* [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-03-17 20:50 ` David Rivshin
0 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-03-17 20:50 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, 17 Mar 2017 13:54:28 -0500
Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> On 03/17/2017 12:54 PM, David Rivshin wrote:
> > Hi Grygorii,
> >
> > On Fri, 17 Mar 2017 11:45:56 -0500
> > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >
> >> On 03/16/2017 07:57 PM, David Rivshin wrote:
> >>> From: David Rivshin <DRivshin@allworx.com>
> >>>
> >>> omap_gpio_debounce() does not validate that the requested debounce
> >>> is within a range it can handle. Instead it lets the register value
> >>> wrap silently, and always returns success.
> >>>
> >>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> >>> asking for a too-long debounce, but getting a very short debounce in
> >>> practice.
> >>>
> >>> Fix this by returning -EINVAL if the requested value does not fit into
> >>> the register field. If there is no debounce clock available at all,
> >>> return -ENOTSUPP.
> >>
> >> In general this patch looks good, but there is one thing I'm worry about..
> >>
> >>>
> >>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> >>> Cc: <stable@vger.kernel.org> # 4.3+
> >>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> >>> ---
> >>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> >>> 1 file changed, 11 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> >>> index efc85a2..33ec02d 100644
> >>> --- a/drivers/gpio/gpio-omap.c
> >>> +++ b/drivers/gpio/gpio-omap.c
> >>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> >>> * OMAP's debounce time is in 31us steps
> >>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> >>> * so we need to convert and round up to the closest unit.
> >>> + *
> >>> + * Return: 0 on success, negative error otherwise.
> >>> */
> >>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> unsigned debounce)
> >>> {
> >>> void __iomem *reg;
> >>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> bool enable = !!debounce;
> >>>
> >>> if (!bank->dbck_flag)
> >>> - return;
> >>> + return -ENOTSUPP;
> >>>
> >>> if (enable) {
> >>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> >>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> >>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> >>> + return -EINVAL;
> >>
> >> This might cause boot issues as current drivers may expect this op to succeed even if
> >> configured value is wrong - just think, may be we can do warn here and use max value as
> >> fallback?
> >
> > I have not looked through all drivers to be sure, but at least the gpio-keys
> > driver requires set_debounce to return an error if it can't satisfy the request.
> > In that case gpio-keys will use a software timer instead.
> >
> > if (button->debounce_interval) {
> > error = gpiod_set_debounce(bdata->gpiod,
> > button->debounce_interval * 1000);
> > /* use timer if gpiolib doesn't provide debounce */
> > if (error < 0)
> > bdata->software_debounce =
> > button->debounce_interval;
> > }
> >
> > Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> > such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> > callback at all. So I expect all drivers which use gpiod_set_debounce() to
> > handle error returns gracefully.
> >
> > So I certainly understand the concern about backwards compatibility, but I
> > think clipping to max is the greater of the evils in this case. Even a
> > warning may be too much, because it's not necessarily anything wrong.
> > Perhaps an info or debug message would be helpful, though?
> >
> > If you prefer, I can try to go through all callers of gpiod_set_debounce()
> > and see how they'd handle an error return. The handful I've looked through so
> > far all behave like gpio-keys. The only ones I'd be particularly concerned
> > about are platform-specific drivers which were perhaps never used with other
> > gpio drivers. Do you know of that I should pay special attention to?
>
> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> As result, even gpio-keys driver will just silently switch to software_debounce
> without any notification.
I think that switching to software_debounce silently is exactly the
intended/desired behavior of gpio-keys (and other drivers). For example,
if the DT requests a 20ms debounce on a gpio-key, the existing math
resulted in a hardware debounce of just 2ms. With the error return,
gpio-keys would silently switch to software_debounce of the requested
20ms (potentially longer if the CPU is busy, but I don't think that's
a problem for correctness), exactly what the DT asked for.
Of course that would be a change in behavior for any such existing DT,
and it's conceivable that the DT for some HW is somehow relying on that
previous incorrect behavior. I suspect it's more likely that they are
silently broken, and no-one has noticed. A quick search of some in-tree
DTs finds most debounce times are 5ms (which has no issue), and then
these three examples (all happen to be gpio-keys):
am335x-shc.dts: debounce-interval = <1000>;
am335x-shc.dts: debounce-interval = <1000>;
omap5-uevm.dts: debounce_interval = <50>;
The first two currently result in a HW debounce of about 4ms. The
third would be 2.5ms, except it's the wrong property name so it
does nothing (it gets the default gpio-keys debounce of 5ms).
Not having seen any of that hardware, I can't say for certain what the
true HW requirements are. 1000ms does seem like a long debounce, perhaps
the author meant 1ms (1000us) for those buttons? Or perhaps it really
needs a 1000ms debounce, and is currently wrong?
>
> But agree - max might not be a good choose, so can you add dev_err() below, pls.
Given the above, I personally feel that a dev_err() is undesirable in most
cases. If I have a system and matching DT that just happens to need a longer
debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
anything to be fixed.
I can understanding wanting to draw attention to a change in behavior (just
in case the DT is incorrect), but I'd personally lean towards dev_info() if
anything.
That said: if you still prefer dev_err(), I will certainly do so.
Tangent:
This discussion makes me think that adding a gpiod_get_max_debounce()
would allow even better behavior. Then asking for a too-high debounce
could be a dev_err() in all gpio drivers, with the expectation that no
driver should ask for such. Also, drivers could do something like use
max hardware debounce plus a software debounce for the remaining time,
in order to avoid CPU overhead on short glitches.
> >>
> >>> }
> >>>
> >>> l = BIT(offset);
> >>> @@ -255,6 +258,8 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> bank->context.debounce = debounce;
> >>> bank->context.debounce_en = val;
> >>> }
> >>> +
> >>> + return 0;
> >>> }
> >>>
> >>> /**
> >>> @@ -964,14 +969,15 @@ static int omap_gpio_debounce(struct gpio_chip *chip, unsigned offset,
> >>> {
> >>> struct gpio_bank *bank;
> >>> unsigned long flags;
> >>> + int ret;
> >>>
> >>> bank = gpiochip_get_data(chip);
> >>>
> >>> raw_spin_lock_irqsave(&bank->lock, flags);
> >>> - omap2_set_gpio_debounce(bank, offset, debounce);
> >>> + ret = omap2_set_gpio_debounce(bank, offset, debounce);
> >>> raw_spin_unlock_irqrestore(&bank->lock, flags);
>
> if (ret) dev_err();
>
> >>>
> >>> - return 0;
> >>> + return ret;
> >>> }
> >>>
> >>> static int omap_gpio_set_config(struct gpio_chip *chip, unsigned offset,
> >>>
> >>
> >
> >
>
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-03-17 20:50 ` David Rivshin
0 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-03-17 20:50 UTC (permalink / raw)
To: Grygorii Strashko
Cc: linux-gpio, linux-omap, Santosh Shilimkar, Kevin Hilman,
Linus Walleij, Alexandre Courbot, linux-arm-kernel, linux-kernel,
stable
On Fri, 17 Mar 2017 13:54:28 -0500
Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> On 03/17/2017 12:54 PM, David Rivshin wrote:
> > Hi Grygorii,
> >
> > On Fri, 17 Mar 2017 11:45:56 -0500
> > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >
> >> On 03/16/2017 07:57 PM, David Rivshin wrote:
> >>> From: David Rivshin <DRivshin@allworx.com>
> >>>
> >>> omap_gpio_debounce() does not validate that the requested debounce
> >>> is within a range it can handle. Instead it lets the register value
> >>> wrap silently, and always returns success.
> >>>
> >>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> >>> asking for a too-long debounce, but getting a very short debounce in
> >>> practice.
> >>>
> >>> Fix this by returning -EINVAL if the requested value does not fit into
> >>> the register field. If there is no debounce clock available at all,
> >>> return -ENOTSUPP.
> >>
> >> In general this patch looks good, but there is one thing I'm worry about..
> >>
> >>>
> >>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> >>> Cc: <stable@vger.kernel.org> # 4.3+
> >>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> >>> ---
> >>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> >>> 1 file changed, 11 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> >>> index efc85a2..33ec02d 100644
> >>> --- a/drivers/gpio/gpio-omap.c
> >>> +++ b/drivers/gpio/gpio-omap.c
> >>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> >>> * OMAP's debounce time is in 31us steps
> >>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> >>> * so we need to convert and round up to the closest unit.
> >>> + *
> >>> + * Return: 0 on success, negative error otherwise.
> >>> */
> >>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> unsigned debounce)
> >>> {
> >>> void __iomem *reg;
> >>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> bool enable = !!debounce;
> >>>
> >>> if (!bank->dbck_flag)
> >>> - return;
> >>> + return -ENOTSUPP;
> >>>
> >>> if (enable) {
> >>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> >>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> >>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> >>> + return -EINVAL;
> >>
> >> This might cause boot issues as current drivers may expect this op to succeed even if
> >> configured value is wrong - just think, may be we can do warn here and use max value as
> >> fallback?
> >
> > I have not looked through all drivers to be sure, but at least the gpio-keys
> > driver requires set_debounce to return an error if it can't satisfy the request.
> > In that case gpio-keys will use a software timer instead.
> >
> > if (button->debounce_interval) {
> > error = gpiod_set_debounce(bdata->gpiod,
> > button->debounce_interval * 1000);
> > /* use timer if gpiolib doesn't provide debounce */
> > if (error < 0)
> > bdata->software_debounce =
> > button->debounce_interval;
> > }
> >
> > Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> > such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> > callback at all. So I expect all drivers which use gpiod_set_debounce() to
> > handle error returns gracefully.
> >
> > So I certainly understand the concern about backwards compatibility, but I
> > think clipping to max is the greater of the evils in this case. Even a
> > warning may be too much, because it's not necessarily anything wrong.
> > Perhaps an info or debug message would be helpful, though?
> >
> > If you prefer, I can try to go through all callers of gpiod_set_debounce()
> > and see how they'd handle an error return. The handful I've looked through so
> > far all behave like gpio-keys. The only ones I'd be particularly concerned
> > about are platform-specific drivers which were perhaps never used with other
> > gpio drivers. Do you know of that I should pay special attention to?
>
> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> As result, even gpio-keys driver will just silently switch to software_debounce
> without any notification.
I think that switching to software_debounce silently is exactly the
intended/desired behavior of gpio-keys (and other drivers). For example,
if the DT requests a 20ms debounce on a gpio-key, the existing math
resulted in a hardware debounce of just 2ms. With the error return,
gpio-keys would silently switch to software_debounce of the requested
20ms (potentially longer if the CPU is busy, but I don't think that's
a problem for correctness), exactly what the DT asked for.
Of course that would be a change in behavior for any such existing DT,
and it's conceivable that the DT for some HW is somehow relying on that
previous incorrect behavior. I suspect it's more likely that they are
silently broken, and no-one has noticed. A quick search of some in-tree
DTs finds most debounce times are 5ms (which has no issue), and then
these three examples (all happen to be gpio-keys):
am335x-shc.dts: debounce-interval = <1000>;
am335x-shc.dts: debounce-interval = <1000>;
omap5-uevm.dts: debounce_interval = <50>;
The first two currently result in a HW debounce of about 4ms. The
third would be 2.5ms, except it's the wrong property name so it
does nothing (it gets the default gpio-keys debounce of 5ms).
Not having seen any of that hardware, I can't say for certain what the
true HW requirements are. 1000ms does seem like a long debounce, perhaps
the author meant 1ms (1000us) for those buttons? Or perhaps it really
needs a 1000ms debounce, and is currently wrong?
>
> But agree - max might not be a good choose, so can you add dev_err() below, pls.
Given the above, I personally feel that a dev_err() is undesirable in most
cases. If I have a system and matching DT that just happens to need a longer
debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
anything to be fixed.
I can understanding wanting to draw attention to a change in behavior (just
in case the DT is incorrect), but I'd personally lean towards dev_info() if
anything.
That said: if you still prefer dev_err(), I will certainly do so.
Tangent:
This discussion makes me think that adding a gpiod_get_max_debounce()
would allow even better behavior. Then asking for a too-high debounce
could be a dev_err() in all gpio drivers, with the expectation that no
driver should ask for such. Also, drivers could do something like use
max hardware debounce plus a software debounce for the remaining time,
in order to avoid CPU overhead on short glitches.
> >>
> >>> }
> >>>
> >>> l = BIT(offset);
> >>> @@ -255,6 +258,8 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>> bank->context.debounce = debounce;
> >>> bank->context.debounce_en = val;
> >>> }
> >>> +
> >>> + return 0;
> >>> }
> >>>
> >>> /**
> >>> @@ -964,14 +969,15 @@ static int omap_gpio_debounce(struct gpio_chip *chip, unsigned offset,
> >>> {
> >>> struct gpio_bank *bank;
> >>> unsigned long flags;
> >>> + int ret;
> >>>
> >>> bank = gpiochip_get_data(chip);
> >>>
> >>> raw_spin_lock_irqsave(&bank->lock, flags);
> >>> - omap2_set_gpio_debounce(bank, offset, debounce);
> >>> + ret = omap2_set_gpio_debounce(bank, offset, debounce);
> >>> raw_spin_unlock_irqrestore(&bank->lock, flags);
>
> if (ret) dev_err();
>
> >>>
> >>> - return 0;
> >>> + return ret;
> >>> }
> >>>
> >>> static int omap_gpio_set_config(struct gpio_chip *chip, unsigned offset,
> >>>
> >>
> >
> >
>
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
2017-03-17 20:50 ` David Rivshin
(?)
@ 2017-03-17 21:43 ` Grygorii Strashko
-1 siblings, 0 replies; 35+ messages in thread
From: Grygorii Strashko @ 2017-03-17 21:43 UTC (permalink / raw)
To: David Rivshin
Cc: Alexandre Courbot, Kevin Hilman, Linus Walleij, linux-kernel,
stable, linux-gpio, Santosh Shilimkar, linux-omap,
linux-arm-kernel
On 03/17/2017 03:50 PM, David Rivshin wrote:
> On Fri, 17 Mar 2017 13:54:28 -0500
> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>
>> On 03/17/2017 12:54 PM, David Rivshin wrote:
>>> Hi Grygorii,
>>>
>>> On Fri, 17 Mar 2017 11:45:56 -0500
>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>
>>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
>>>>> From: David Rivshin <DRivshin@allworx.com>
>>>>>
>>>>> omap_gpio_debounce() does not validate that the requested debounce
>>>>> is within a range it can handle. Instead it lets the register value
>>>>> wrap silently, and always returns success.
>>>>>
>>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
>>>>> asking for a too-long debounce, but getting a very short debounce in
>>>>> practice.
>>>>>
>>>>> Fix this by returning -EINVAL if the requested value does not fit into
>>>>> the register field. If there is no debounce clock available at all,
>>>>> return -ENOTSUPP.
>>>>
>>>> In general this patch looks good, but there is one thing I'm worry about..
>>>>
>>>>>
>>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
>>>>> Cc: <stable@vger.kernel.org> # 4.3+
>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>> ---
>>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
>>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>>> index efc85a2..33ec02d 100644
>>>>> --- a/drivers/gpio/gpio-omap.c
>>>>> +++ b/drivers/gpio/gpio-omap.c
>>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
>>>>> * OMAP's debounce time is in 31us steps
>>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
>>>>> * so we need to convert and round up to the closest unit.
>>>>> + *
>>>>> + * Return: 0 on success, negative error otherwise.
>>>>> */
>>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> unsigned debounce)
>>>>> {
>>>>> void __iomem *reg;
>>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> bool enable = !!debounce;
>>>>>
>>>>> if (!bank->dbck_flag)
>>>>> - return;
>>>>> + return -ENOTSUPP;
>>>>>
>>>>> if (enable) {
>>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
>>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
>>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
>>>>> + return -EINVAL;
>>>>
>>>> This might cause boot issues as current drivers may expect this op to succeed even if
>>>> configured value is wrong - just think, may be we can do warn here and use max value as
>>>> fallback?
>>>
>>> I have not looked through all drivers to be sure, but at least the gpio-keys
>>> driver requires set_debounce to return an error if it can't satisfy the request.
>>> In that case gpio-keys will use a software timer instead.
>>>
>>> if (button->debounce_interval) {
>>> error = gpiod_set_debounce(bdata->gpiod,
>>> button->debounce_interval * 1000);
>>> /* use timer if gpiolib doesn't provide debounce */
>>> if (error < 0)
>>> bdata->software_debounce =
>>> button->debounce_interval;
>>> }
>>>
>>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
>>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
>>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
>>> handle error returns gracefully.
>>>
>>> So I certainly understand the concern about backwards compatibility, but I
>>> think clipping to max is the greater of the evils in this case. Even a
>>> warning may be too much, because it's not necessarily anything wrong.
>>> Perhaps an info or debug message would be helpful, though?
>>>
>>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
>>> and see how they'd handle an error return. The handful I've looked through so
>>> far all behave like gpio-keys. The only ones I'd be particularly concerned
>>> about are platform-specific drivers which were perhaps never used with other
>>> gpio drivers. Do you know of that I should pay special attention to?
>>
>> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
>> As result, even gpio-keys driver will just silently switch to software_debounce
>> without any notification.
>
> I think that switching to software_debounce silently is exactly the
> intended/desired behavior of gpio-keys (and other drivers). For example,
> if the DT requests a 20ms debounce on a gpio-key, the existing math
> resulted in a hardware debounce of just 2ms. With the error return,
> gpio-keys would silently switch to software_debounce of the requested
> 20ms (potentially longer if the CPU is busy, but I don't think that's
> a problem for correctness), exactly what the DT asked for.
>
> Of course that would be a change in behavior for any such existing DT,
> and it's conceivable that the DT for some HW is somehow relying on that
> previous incorrect behavior. I suspect it's more likely that they are
> silently broken, and no-one has noticed. A quick search of some in-tree
> DTs finds most debounce times are 5ms (which has no issue), and then
> these three examples (all happen to be gpio-keys):
> am335x-shc.dts: debounce-interval = <1000>;
> am335x-shc.dts: debounce-interval = <1000>;
> omap5-uevm.dts: debounce_interval = <50>;
> The first two currently result in a HW debounce of about 4ms. The
> third would be 2.5ms, except it's the wrong property name so it
> does nothing (it gets the default gpio-keys debounce of 5ms).
Yep. looks like error in dt. There are mod such DTs actually
./arch/arm/boot/dts/atlas7-evb.dts
./arch/arm/boot/dts/emev2-kzm9d.dts
./arch/arm/boot/dts/kirkwood-pogoplug-series-4.dts
./arch/arm/boot/dts/omap5-uevm.dts
./arch/arm/boot/dts/ste-snowball.dts
>
> Not having seen any of that hardware, I can't say for certain what the
> true HW requirements are. 1000ms does seem like a long debounce, perhaps
> the author meant 1ms (1000us) for those buttons? Or perhaps it really
> needs a 1000ms debounce, and is currently wrong?
>
>>
>> But agree - max might not be a good choose, so can you add dev_err() below, pls.
>
> Given the above, I personally feel that a dev_err() is undesirable in most
> cases. If I have a system and matching DT that just happens to need a longer
> debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> anything to be fixed.
> I can understanding wanting to draw attention to a change in behavior (just
> in case the DT is incorrect), but I'd personally lean towards dev_info() if
> anything.
>
> That said: if you still prefer dev_err(), I will certainly do so.
Fair enough :) thanks.
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
>
> Tangent:
> This discussion makes me think that adding a gpiod_get_max_debounce()
> would allow even better behavior. Then asking for a too-high debounce
> could be a dev_err() in all gpio drivers, with the expectation that no
> driver should ask for such. Also, drivers could do something like use
> max hardware debounce plus a software debounce for the remaining time,
> in order to avoid CPU overhead on short glitches.
>
>
--
regards,
-grygorii
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-03-17 21:43 ` Grygorii Strashko
0 siblings, 0 replies; 35+ messages in thread
From: Grygorii Strashko @ 2017-03-17 21:43 UTC (permalink / raw)
To: linux-arm-kernel
On 03/17/2017 03:50 PM, David Rivshin wrote:
> On Fri, 17 Mar 2017 13:54:28 -0500
> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>
>> On 03/17/2017 12:54 PM, David Rivshin wrote:
>>> Hi Grygorii,
>>>
>>> On Fri, 17 Mar 2017 11:45:56 -0500
>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>
>>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
>>>>> From: David Rivshin <DRivshin@allworx.com>
>>>>>
>>>>> omap_gpio_debounce() does not validate that the requested debounce
>>>>> is within a range it can handle. Instead it lets the register value
>>>>> wrap silently, and always returns success.
>>>>>
>>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
>>>>> asking for a too-long debounce, but getting a very short debounce in
>>>>> practice.
>>>>>
>>>>> Fix this by returning -EINVAL if the requested value does not fit into
>>>>> the register field. If there is no debounce clock available at all,
>>>>> return -ENOTSUPP.
>>>>
>>>> In general this patch looks good, but there is one thing I'm worry about..
>>>>
>>>>>
>>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
>>>>> Cc: <stable@vger.kernel.org> # 4.3+
>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>> ---
>>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
>>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>>> index efc85a2..33ec02d 100644
>>>>> --- a/drivers/gpio/gpio-omap.c
>>>>> +++ b/drivers/gpio/gpio-omap.c
>>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
>>>>> * OMAP's debounce time is in 31us steps
>>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
>>>>> * so we need to convert and round up to the closest unit.
>>>>> + *
>>>>> + * Return: 0 on success, negative error otherwise.
>>>>> */
>>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> unsigned debounce)
>>>>> {
>>>>> void __iomem *reg;
>>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> bool enable = !!debounce;
>>>>>
>>>>> if (!bank->dbck_flag)
>>>>> - return;
>>>>> + return -ENOTSUPP;
>>>>>
>>>>> if (enable) {
>>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
>>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
>>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
>>>>> + return -EINVAL;
>>>>
>>>> This might cause boot issues as current drivers may expect this op to succeed even if
>>>> configured value is wrong - just think, may be we can do warn here and use max value as
>>>> fallback?
>>>
>>> I have not looked through all drivers to be sure, but at least the gpio-keys
>>> driver requires set_debounce to return an error if it can't satisfy the request.
>>> In that case gpio-keys will use a software timer instead.
>>>
>>> if (button->debounce_interval) {
>>> error = gpiod_set_debounce(bdata->gpiod,
>>> button->debounce_interval * 1000);
>>> /* use timer if gpiolib doesn't provide debounce */
>>> if (error < 0)
>>> bdata->software_debounce =
>>> button->debounce_interval;
>>> }
>>>
>>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
>>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
>>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
>>> handle error returns gracefully.
>>>
>>> So I certainly understand the concern about backwards compatibility, but I
>>> think clipping to max is the greater of the evils in this case. Even a
>>> warning may be too much, because it's not necessarily anything wrong.
>>> Perhaps an info or debug message would be helpful, though?
>>>
>>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
>>> and see how they'd handle an error return. The handful I've looked through so
>>> far all behave like gpio-keys. The only ones I'd be particularly concerned
>>> about are platform-specific drivers which were perhaps never used with other
>>> gpio drivers. Do you know of that I should pay special attention to?
>>
>> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
>> As result, even gpio-keys driver will just silently switch to software_debounce
>> without any notification.
>
> I think that switching to software_debounce silently is exactly the
> intended/desired behavior of gpio-keys (and other drivers). For example,
> if the DT requests a 20ms debounce on a gpio-key, the existing math
> resulted in a hardware debounce of just 2ms. With the error return,
> gpio-keys would silently switch to software_debounce of the requested
> 20ms (potentially longer if the CPU is busy, but I don't think that's
> a problem for correctness), exactly what the DT asked for.
>
> Of course that would be a change in behavior for any such existing DT,
> and it's conceivable that the DT for some HW is somehow relying on that
> previous incorrect behavior. I suspect it's more likely that they are
> silently broken, and no-one has noticed. A quick search of some in-tree
> DTs finds most debounce times are 5ms (which has no issue), and then
> these three examples (all happen to be gpio-keys):
> am335x-shc.dts: debounce-interval = <1000>;
> am335x-shc.dts: debounce-interval = <1000>;
> omap5-uevm.dts: debounce_interval = <50>;
> The first two currently result in a HW debounce of about 4ms. The
> third would be 2.5ms, except it's the wrong property name so it
> does nothing (it gets the default gpio-keys debounce of 5ms).
Yep. looks like error in dt. There are mod such DTs actually
./arch/arm/boot/dts/atlas7-evb.dts
./arch/arm/boot/dts/emev2-kzm9d.dts
./arch/arm/boot/dts/kirkwood-pogoplug-series-4.dts
./arch/arm/boot/dts/omap5-uevm.dts
./arch/arm/boot/dts/ste-snowball.dts
>
> Not having seen any of that hardware, I can't say for certain what the
> true HW requirements are. 1000ms does seem like a long debounce, perhaps
> the author meant 1ms (1000us) for those buttons? Or perhaps it really
> needs a 1000ms debounce, and is currently wrong?
>
>>
>> But agree - max might not be a good choose, so can you add dev_err() below, pls.
>
> Given the above, I personally feel that a dev_err() is undesirable in most
> cases. If I have a system and matching DT that just happens to need a longer
> debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> anything to be fixed.
> I can understanding wanting to draw attention to a change in behavior (just
> in case the DT is incorrect), but I'd personally lean towards dev_info() if
> anything.
>
> That said: if you still prefer dev_err(), I will certainly do so.
Fair enough :) thanks.
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
>
> Tangent:
> This discussion makes me think that adding a gpiod_get_max_debounce()
> would allow even better behavior. Then asking for a too-high debounce
> could be a dev_err() in all gpio drivers, with the expectation that no
> driver should ask for such. Also, drivers could do something like use
> max hardware debounce plus a software debounce for the remaining time,
> in order to avoid CPU overhead on short glitches.
>
>
--
regards,
-grygorii
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-03-17 21:43 ` Grygorii Strashko
0 siblings, 0 replies; 35+ messages in thread
From: Grygorii Strashko @ 2017-03-17 21:43 UTC (permalink / raw)
To: David Rivshin
Cc: linux-gpio, linux-omap, Santosh Shilimkar, Kevin Hilman,
Linus Walleij, Alexandre Courbot, linux-arm-kernel, linux-kernel,
stable
On 03/17/2017 03:50 PM, David Rivshin wrote:
> On Fri, 17 Mar 2017 13:54:28 -0500
> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>
>> On 03/17/2017 12:54 PM, David Rivshin wrote:
>>> Hi Grygorii,
>>>
>>> On Fri, 17 Mar 2017 11:45:56 -0500
>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>
>>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
>>>>> From: David Rivshin <DRivshin@allworx.com>
>>>>>
>>>>> omap_gpio_debounce() does not validate that the requested debounce
>>>>> is within a range it can handle. Instead it lets the register value
>>>>> wrap silently, and always returns success.
>>>>>
>>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
>>>>> asking for a too-long debounce, but getting a very short debounce in
>>>>> practice.
>>>>>
>>>>> Fix this by returning -EINVAL if the requested value does not fit into
>>>>> the register field. If there is no debounce clock available at all,
>>>>> return -ENOTSUPP.
>>>>
>>>> In general this patch looks good, but there is one thing I'm worry about..
>>>>
>>>>>
>>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
>>>>> Cc: <stable@vger.kernel.org> # 4.3+
>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>> ---
>>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
>>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>>> index efc85a2..33ec02d 100644
>>>>> --- a/drivers/gpio/gpio-omap.c
>>>>> +++ b/drivers/gpio/gpio-omap.c
>>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
>>>>> * OMAP's debounce time is in 31us steps
>>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
>>>>> * so we need to convert and round up to the closest unit.
>>>>> + *
>>>>> + * Return: 0 on success, negative error otherwise.
>>>>> */
>>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> unsigned debounce)
>>>>> {
>>>>> void __iomem *reg;
>>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>> bool enable = !!debounce;
>>>>>
>>>>> if (!bank->dbck_flag)
>>>>> - return;
>>>>> + return -ENOTSUPP;
>>>>>
>>>>> if (enable) {
>>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
>>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
>>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
>>>>> + return -EINVAL;
>>>>
>>>> This might cause boot issues as current drivers may expect this op to succeed even if
>>>> configured value is wrong - just think, may be we can do warn here and use max value as
>>>> fallback?
>>>
>>> I have not looked through all drivers to be sure, but at least the gpio-keys
>>> driver requires set_debounce to return an error if it can't satisfy the request.
>>> In that case gpio-keys will use a software timer instead.
>>>
>>> if (button->debounce_interval) {
>>> error = gpiod_set_debounce(bdata->gpiod,
>>> button->debounce_interval * 1000);
>>> /* use timer if gpiolib doesn't provide debounce */
>>> if (error < 0)
>>> bdata->software_debounce =
>>> button->debounce_interval;
>>> }
>>>
>>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
>>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
>>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
>>> handle error returns gracefully.
>>>
>>> So I certainly understand the concern about backwards compatibility, but I
>>> think clipping to max is the greater of the evils in this case. Even a
>>> warning may be too much, because it's not necessarily anything wrong.
>>> Perhaps an info or debug message would be helpful, though?
>>>
>>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
>>> and see how they'd handle an error return. The handful I've looked through so
>>> far all behave like gpio-keys. The only ones I'd be particularly concerned
>>> about are platform-specific drivers which were perhaps never used with other
>>> gpio drivers. Do you know of that I should pay special attention to?
>>
>> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
>> As result, even gpio-keys driver will just silently switch to software_debounce
>> without any notification.
>
> I think that switching to software_debounce silently is exactly the
> intended/desired behavior of gpio-keys (and other drivers). For example,
> if the DT requests a 20ms debounce on a gpio-key, the existing math
> resulted in a hardware debounce of just 2ms. With the error return,
> gpio-keys would silently switch to software_debounce of the requested
> 20ms (potentially longer if the CPU is busy, but I don't think that's
> a problem for correctness), exactly what the DT asked for.
>
> Of course that would be a change in behavior for any such existing DT,
> and it's conceivable that the DT for some HW is somehow relying on that
> previous incorrect behavior. I suspect it's more likely that they are
> silently broken, and no-one has noticed. A quick search of some in-tree
> DTs finds most debounce times are 5ms (which has no issue), and then
> these three examples (all happen to be gpio-keys):
> am335x-shc.dts: debounce-interval = <1000>;
> am335x-shc.dts: debounce-interval = <1000>;
> omap5-uevm.dts: debounce_interval = <50>;
> The first two currently result in a HW debounce of about 4ms. The
> third would be 2.5ms, except it's the wrong property name so it
> does nothing (it gets the default gpio-keys debounce of 5ms).
Yep. looks like error in dt. There are mod such DTs actually
./arch/arm/boot/dts/atlas7-evb.dts
./arch/arm/boot/dts/emev2-kzm9d.dts
./arch/arm/boot/dts/kirkwood-pogoplug-series-4.dts
./arch/arm/boot/dts/omap5-uevm.dts
./arch/arm/boot/dts/ste-snowball.dts
>
> Not having seen any of that hardware, I can't say for certain what the
> true HW requirements are. 1000ms does seem like a long debounce, perhaps
> the author meant 1ms (1000us) for those buttons? Or perhaps it really
> needs a 1000ms debounce, and is currently wrong?
>
>>
>> But agree - max might not be a good choose, so can you add dev_err() below, pls.
>
> Given the above, I personally feel that a dev_err() is undesirable in most
> cases. If I have a system and matching DT that just happens to need a longer
> debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> anything to be fixed.
> I can understanding wanting to draw attention to a change in behavior (just
> in case the DT is incorrect), but I'd personally lean towards dev_info() if
> anything.
>
> That said: if you still prefer dev_err(), I will certainly do so.
Fair enough :) thanks.
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
>
> Tangent:
> This discussion makes me think that adding a gpiod_get_max_debounce()
> would allow even better behavior. Then asking for a too-high debounce
> could be a dev_err() in all gpio drivers, with the expectation that no
> driver should ask for such. Also, drivers could do something like use
> max hardware debounce plus a software debounce for the remaining time,
> in order to avoid CPU overhead on short glitches.
>
>
--
regards,
-grygorii
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
2017-03-17 21:43 ` Grygorii Strashko
(?)
@ 2017-03-17 23:42 ` David Rivshin
-1 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-03-17 23:42 UTC (permalink / raw)
To: Grygorii Strashko
Cc: Alexandre Courbot, Kevin Hilman, Linus Walleij, linux-kernel,
stable, linux-gpio, Santosh Shilimkar, linux-omap,
linux-arm-kernel
On Fri, 17 Mar 2017 16:43:56 -0500
Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> On 03/17/2017 03:50 PM, David Rivshin wrote:
> > On Fri, 17 Mar 2017 13:54:28 -0500
> > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >
> >> On 03/17/2017 12:54 PM, David Rivshin wrote:
> >>> Hi Grygorii,
> >>>
> >>> On Fri, 17 Mar 2017 11:45:56 -0500
> >>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >>>
> >>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
> >>>>> From: David Rivshin <DRivshin@allworx.com>
> >>>>>
> >>>>> omap_gpio_debounce() does not validate that the requested debounce
> >>>>> is within a range it can handle. Instead it lets the register value
> >>>>> wrap silently, and always returns success.
> >>>>>
> >>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> >>>>> asking for a too-long debounce, but getting a very short debounce in
> >>>>> practice.
> >>>>>
> >>>>> Fix this by returning -EINVAL if the requested value does not fit into
> >>>>> the register field. If there is no debounce clock available at all,
> >>>>> return -ENOTSUPP.
> >>>>
> >>>> In general this patch looks good, but there is one thing I'm worry about..
> >>>>
> >>>>>
> >>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> >>>>> Cc: <stable@vger.kernel.org> # 4.3+
> >>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> >>>>> ---
> >>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> >>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> >>>>> index efc85a2..33ec02d 100644
> >>>>> --- a/drivers/gpio/gpio-omap.c
> >>>>> +++ b/drivers/gpio/gpio-omap.c
> >>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> >>>>> * OMAP's debounce time is in 31us steps
> >>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> >>>>> * so we need to convert and round up to the closest unit.
> >>>>> + *
> >>>>> + * Return: 0 on success, negative error otherwise.
> >>>>> */
> >>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> unsigned debounce)
> >>>>> {
> >>>>> void __iomem *reg;
> >>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> bool enable = !!debounce;
> >>>>>
> >>>>> if (!bank->dbck_flag)
> >>>>> - return;
> >>>>> + return -ENOTSUPP;
> >>>>>
> >>>>> if (enable) {
> >>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> >>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> >>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> >>>>> + return -EINVAL;
> >>>>
> >>>> This might cause boot issues as current drivers may expect this op to succeed even if
> >>>> configured value is wrong - just think, may be we can do warn here and use max value as
> >>>> fallback?
> >>>
> >>> I have not looked through all drivers to be sure, but at least the gpio-keys
> >>> driver requires set_debounce to return an error if it can't satisfy the request.
> >>> In that case gpio-keys will use a software timer instead.
> >>>
> >>> if (button->debounce_interval) {
> >>> error = gpiod_set_debounce(bdata->gpiod,
> >>> button->debounce_interval * 1000);
> >>> /* use timer if gpiolib doesn't provide debounce */
> >>> if (error < 0)
> >>> bdata->software_debounce =
> >>> button->debounce_interval;
> >>> }
> >>>
> >>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> >>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> >>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
> >>> handle error returns gracefully.
> >>>
> >>> So I certainly understand the concern about backwards compatibility, but I
> >>> think clipping to max is the greater of the evils in this case. Even a
> >>> warning may be too much, because it's not necessarily anything wrong.
> >>> Perhaps an info or debug message would be helpful, though?
> >>>
> >>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
> >>> and see how they'd handle an error return. The handful I've looked through so
> >>> far all behave like gpio-keys. The only ones I'd be particularly concerned
> >>> about are platform-specific drivers which were perhaps never used with other
> >>> gpio drivers. Do you know of that I should pay special attention to?
> >>
> >> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> >> As result, even gpio-keys driver will just silently switch to software_debounce
> >> without any notification.
> >
> > I think that switching to software_debounce silently is exactly the
> > intended/desired behavior of gpio-keys (and other drivers). For example,
> > if the DT requests a 20ms debounce on a gpio-key, the existing math
> > resulted in a hardware debounce of just 2ms. With the error return,
> > gpio-keys would silently switch to software_debounce of the requested
> > 20ms (potentially longer if the CPU is busy, but I don't think that's
> > a problem for correctness), exactly what the DT asked for.
> >
> > Of course that would be a change in behavior for any such existing DT,
> > and it's conceivable that the DT for some HW is somehow relying on that
> > previous incorrect behavior. I suspect it's more likely that they are
> > silently broken, and no-one has noticed. A quick search of some in-tree
> > DTs finds most debounce times are 5ms (which has no issue), and then
> > these three examples (all happen to be gpio-keys):
> > am335x-shc.dts: debounce-interval = <1000>;
> > am335x-shc.dts: debounce-interval = <1000>;
> > omap5-uevm.dts: debounce_interval = <50>;
> > The first two currently result in a HW debounce of about 4ms. The
> > third would be 2.5ms, except it's the wrong property name so it
> > does nothing (it gets the default gpio-keys debounce of 5ms).
>
> Yep. looks like error in dt. There are mod such DTs actually
> ./arch/arm/boot/dts/atlas7-evb.dts
> ./arch/arm/boot/dts/emev2-kzm9d.dts
> ./arch/arm/boot/dts/kirkwood-pogoplug-series-4.dts
> ./arch/arm/boot/dts/omap5-uevm.dts
> ./arch/arm/boot/dts/ste-snowball.dts
Ah yes, I just grepped for 'debounce' in am* and omap*. I guess
that typo has been copied over from DT to DT. I'm tempted to spin
a patch correcting the typo, but I have no knowledge of those
boards or HW to test with. Obviously no-one has complained about
the 5ms vs 50ms debounce so far, so maybe 50ms isn't the correct
number in the first place?
> >
> > Not having seen any of that hardware, I can't say for certain what the
> > true HW requirements are. 1000ms does seem like a long debounce, perhaps
> > the author meant 1ms (1000us) for those buttons? Or perhaps it really
> > needs a 1000ms debounce, and is currently wrong?
> >
> >>
> >> But agree - max might not be a good choose, so can you add dev_err() below, pls.
> >
> > Given the above, I personally feel that a dev_err() is undesirable in most
> > cases. If I have a system and matching DT that just happens to need a longer
> > debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> > anything to be fixed.
> > I can understanding wanting to draw attention to a change in behavior (just
> > in case the DT is incorrect), but I'd personally lean towards dev_info() if
> > anything.
> >
> > That said: if you still prefer dev_err(), I will certainly do so.
>
> Fair enough :) thanks.
>
> Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Just to make sure I don't misunderstand, would you like me to:
A) put in a dev_err()
B) put in a dev_info()
C) leave it as-is without any message
?
I can spin a v2 as early as Monday, depending on the results of discussion
on the second patch.
>
> >
> > Tangent:
> > This discussion makes me think that adding a gpiod_get_max_debounce()
> > would allow even better behavior. Then asking for a too-high debounce
> > could be a dev_err() in all gpio drivers, with the expectation that no
> > driver should ask for such. Also, drivers could do something like use
> > max hardware debounce plus a software debounce for the remaining time,
> > in order to avoid CPU overhead on short glitches.
> >
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-03-17 23:42 ` David Rivshin
0 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-03-17 23:42 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, 17 Mar 2017 16:43:56 -0500
Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> On 03/17/2017 03:50 PM, David Rivshin wrote:
> > On Fri, 17 Mar 2017 13:54:28 -0500
> > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >
> >> On 03/17/2017 12:54 PM, David Rivshin wrote:
> >>> Hi Grygorii,
> >>>
> >>> On Fri, 17 Mar 2017 11:45:56 -0500
> >>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >>>
> >>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
> >>>>> From: David Rivshin <DRivshin@allworx.com>
> >>>>>
> >>>>> omap_gpio_debounce() does not validate that the requested debounce
> >>>>> is within a range it can handle. Instead it lets the register value
> >>>>> wrap silently, and always returns success.
> >>>>>
> >>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> >>>>> asking for a too-long debounce, but getting a very short debounce in
> >>>>> practice.
> >>>>>
> >>>>> Fix this by returning -EINVAL if the requested value does not fit into
> >>>>> the register field. If there is no debounce clock available at all,
> >>>>> return -ENOTSUPP.
> >>>>
> >>>> In general this patch looks good, but there is one thing I'm worry about..
> >>>>
> >>>>>
> >>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> >>>>> Cc: <stable@vger.kernel.org> # 4.3+
> >>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> >>>>> ---
> >>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> >>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> >>>>> index efc85a2..33ec02d 100644
> >>>>> --- a/drivers/gpio/gpio-omap.c
> >>>>> +++ b/drivers/gpio/gpio-omap.c
> >>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> >>>>> * OMAP's debounce time is in 31us steps
> >>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> >>>>> * so we need to convert and round up to the closest unit.
> >>>>> + *
> >>>>> + * Return: 0 on success, negative error otherwise.
> >>>>> */
> >>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> unsigned debounce)
> >>>>> {
> >>>>> void __iomem *reg;
> >>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> bool enable = !!debounce;
> >>>>>
> >>>>> if (!bank->dbck_flag)
> >>>>> - return;
> >>>>> + return -ENOTSUPP;
> >>>>>
> >>>>> if (enable) {
> >>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> >>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> >>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> >>>>> + return -EINVAL;
> >>>>
> >>>> This might cause boot issues as current drivers may expect this op to succeed even if
> >>>> configured value is wrong - just think, may be we can do warn here and use max value as
> >>>> fallback?
> >>>
> >>> I have not looked through all drivers to be sure, but at least the gpio-keys
> >>> driver requires set_debounce to return an error if it can't satisfy the request.
> >>> In that case gpio-keys will use a software timer instead.
> >>>
> >>> if (button->debounce_interval) {
> >>> error = gpiod_set_debounce(bdata->gpiod,
> >>> button->debounce_interval * 1000);
> >>> /* use timer if gpiolib doesn't provide debounce */
> >>> if (error < 0)
> >>> bdata->software_debounce =
> >>> button->debounce_interval;
> >>> }
> >>>
> >>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> >>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> >>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
> >>> handle error returns gracefully.
> >>>
> >>> So I certainly understand the concern about backwards compatibility, but I
> >>> think clipping to max is the greater of the evils in this case. Even a
> >>> warning may be too much, because it's not necessarily anything wrong.
> >>> Perhaps an info or debug message would be helpful, though?
> >>>
> >>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
> >>> and see how they'd handle an error return. The handful I've looked through so
> >>> far all behave like gpio-keys. The only ones I'd be particularly concerned
> >>> about are platform-specific drivers which were perhaps never used with other
> >>> gpio drivers. Do you know of that I should pay special attention to?
> >>
> >> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> >> As result, even gpio-keys driver will just silently switch to software_debounce
> >> without any notification.
> >
> > I think that switching to software_debounce silently is exactly the
> > intended/desired behavior of gpio-keys (and other drivers). For example,
> > if the DT requests a 20ms debounce on a gpio-key, the existing math
> > resulted in a hardware debounce of just 2ms. With the error return,
> > gpio-keys would silently switch to software_debounce of the requested
> > 20ms (potentially longer if the CPU is busy, but I don't think that's
> > a problem for correctness), exactly what the DT asked for.
> >
> > Of course that would be a change in behavior for any such existing DT,
> > and it's conceivable that the DT for some HW is somehow relying on that
> > previous incorrect behavior. I suspect it's more likely that they are
> > silently broken, and no-one has noticed. A quick search of some in-tree
> > DTs finds most debounce times are 5ms (which has no issue), and then
> > these three examples (all happen to be gpio-keys):
> > am335x-shc.dts: debounce-interval = <1000>;
> > am335x-shc.dts: debounce-interval = <1000>;
> > omap5-uevm.dts: debounce_interval = <50>;
> > The first two currently result in a HW debounce of about 4ms. The
> > third would be 2.5ms, except it's the wrong property name so it
> > does nothing (it gets the default gpio-keys debounce of 5ms).
>
> Yep. looks like error in dt. There are mod such DTs actually
> ./arch/arm/boot/dts/atlas7-evb.dts
> ./arch/arm/boot/dts/emev2-kzm9d.dts
> ./arch/arm/boot/dts/kirkwood-pogoplug-series-4.dts
> ./arch/arm/boot/dts/omap5-uevm.dts
> ./arch/arm/boot/dts/ste-snowball.dts
Ah yes, I just grepped for 'debounce' in am* and omap*. I guess
that typo has been copied over from DT to DT. I'm tempted to spin
a patch correcting the typo, but I have no knowledge of those
boards or HW to test with. Obviously no-one has complained about
the 5ms vs 50ms debounce so far, so maybe 50ms isn't the correct
number in the first place?
> >
> > Not having seen any of that hardware, I can't say for certain what the
> > true HW requirements are. 1000ms does seem like a long debounce, perhaps
> > the author meant 1ms (1000us) for those buttons? Or perhaps it really
> > needs a 1000ms debounce, and is currently wrong?
> >
> >>
> >> But agree - max might not be a good choose, so can you add dev_err() below, pls.
> >
> > Given the above, I personally feel that a dev_err() is undesirable in most
> > cases. If I have a system and matching DT that just happens to need a longer
> > debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> > anything to be fixed.
> > I can understanding wanting to draw attention to a change in behavior (just
> > in case the DT is incorrect), but I'd personally lean towards dev_info() if
> > anything.
> >
> > That said: if you still prefer dev_err(), I will certainly do so.
>
> Fair enough :) thanks.
>
> Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Just to make sure I don't misunderstand, would you like me to:
A) put in a dev_err()
B) put in a dev_info()
C) leave it as-is without any message
?
I can spin a v2 as early as Monday, depending on the results of discussion
on the second patch.
>
> >
> > Tangent:
> > This discussion makes me think that adding a gpiod_get_max_debounce()
> > would allow even better behavior. Then asking for a too-high debounce
> > could be a dev_err() in all gpio drivers, with the expectation that no
> > driver should ask for such. Also, drivers could do something like use
> > max hardware debounce plus a software debounce for the remaining time,
> > in order to avoid CPU overhead on short glitches.
> >
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-03-17 23:42 ` David Rivshin
0 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-03-17 23:42 UTC (permalink / raw)
To: Grygorii Strashko
Cc: linux-gpio, linux-omap, Santosh Shilimkar, Kevin Hilman,
Linus Walleij, Alexandre Courbot, linux-arm-kernel, linux-kernel,
stable
On Fri, 17 Mar 2017 16:43:56 -0500
Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> On 03/17/2017 03:50 PM, David Rivshin wrote:
> > On Fri, 17 Mar 2017 13:54:28 -0500
> > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >
> >> On 03/17/2017 12:54 PM, David Rivshin wrote:
> >>> Hi Grygorii,
> >>>
> >>> On Fri, 17 Mar 2017 11:45:56 -0500
> >>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> >>>
> >>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
> >>>>> From: David Rivshin <DRivshin@allworx.com>
> >>>>>
> >>>>> omap_gpio_debounce() does not validate that the requested debounce
> >>>>> is within a range it can handle. Instead it lets the register value
> >>>>> wrap silently, and always returns success.
> >>>>>
> >>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> >>>>> asking for a too-long debounce, but getting a very short debounce in
> >>>>> practice.
> >>>>>
> >>>>> Fix this by returning -EINVAL if the requested value does not fit into
> >>>>> the register field. If there is no debounce clock available at all,
> >>>>> return -ENOTSUPP.
> >>>>
> >>>> In general this patch looks good, but there is one thing I'm worry about..
> >>>>
> >>>>>
> >>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> >>>>> Cc: <stable@vger.kernel.org> # 4.3+
> >>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> >>>>> ---
> >>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> >>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> >>>>> index efc85a2..33ec02d 100644
> >>>>> --- a/drivers/gpio/gpio-omap.c
> >>>>> +++ b/drivers/gpio/gpio-omap.c
> >>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> >>>>> * OMAP's debounce time is in 31us steps
> >>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> >>>>> * so we need to convert and round up to the closest unit.
> >>>>> + *
> >>>>> + * Return: 0 on success, negative error otherwise.
> >>>>> */
> >>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> unsigned debounce)
> >>>>> {
> >>>>> void __iomem *reg;
> >>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> >>>>> bool enable = !!debounce;
> >>>>>
> >>>>> if (!bank->dbck_flag)
> >>>>> - return;
> >>>>> + return -ENOTSUPP;
> >>>>>
> >>>>> if (enable) {
> >>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> >>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> >>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> >>>>> + return -EINVAL;
> >>>>
> >>>> This might cause boot issues as current drivers may expect this op to succeed even if
> >>>> configured value is wrong - just think, may be we can do warn here and use max value as
> >>>> fallback?
> >>>
> >>> I have not looked through all drivers to be sure, but at least the gpio-keys
> >>> driver requires set_debounce to return an error if it can't satisfy the request.
> >>> In that case gpio-keys will use a software timer instead.
> >>>
> >>> if (button->debounce_interval) {
> >>> error = gpiod_set_debounce(bdata->gpiod,
> >>> button->debounce_interval * 1000);
> >>> /* use timer if gpiolib doesn't provide debounce */
> >>> if (error < 0)
> >>> bdata->software_debounce =
> >>> button->debounce_interval;
> >>> }
> >>>
> >>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> >>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> >>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
> >>> handle error returns gracefully.
> >>>
> >>> So I certainly understand the concern about backwards compatibility, but I
> >>> think clipping to max is the greater of the evils in this case. Even a
> >>> warning may be too much, because it's not necessarily anything wrong.
> >>> Perhaps an info or debug message would be helpful, though?
> >>>
> >>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
> >>> and see how they'd handle an error return. The handful I've looked through so
> >>> far all behave like gpio-keys. The only ones I'd be particularly concerned
> >>> about are platform-specific drivers which were perhaps never used with other
> >>> gpio drivers. Do you know of that I should pay special attention to?
> >>
> >> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> >> As result, even gpio-keys driver will just silently switch to software_debounce
> >> without any notification.
> >
> > I think that switching to software_debounce silently is exactly the
> > intended/desired behavior of gpio-keys (and other drivers). For example,
> > if the DT requests a 20ms debounce on a gpio-key, the existing math
> > resulted in a hardware debounce of just 2ms. With the error return,
> > gpio-keys would silently switch to software_debounce of the requested
> > 20ms (potentially longer if the CPU is busy, but I don't think that's
> > a problem for correctness), exactly what the DT asked for.
> >
> > Of course that would be a change in behavior for any such existing DT,
> > and it's conceivable that the DT for some HW is somehow relying on that
> > previous incorrect behavior. I suspect it's more likely that they are
> > silently broken, and no-one has noticed. A quick search of some in-tree
> > DTs finds most debounce times are 5ms (which has no issue), and then
> > these three examples (all happen to be gpio-keys):
> > am335x-shc.dts: debounce-interval = <1000>;
> > am335x-shc.dts: debounce-interval = <1000>;
> > omap5-uevm.dts: debounce_interval = <50>;
> > The first two currently result in a HW debounce of about 4ms. The
> > third would be 2.5ms, except it's the wrong property name so it
> > does nothing (it gets the default gpio-keys debounce of 5ms).
>
> Yep. looks like error in dt. There are mod such DTs actually
> ./arch/arm/boot/dts/atlas7-evb.dts
> ./arch/arm/boot/dts/emev2-kzm9d.dts
> ./arch/arm/boot/dts/kirkwood-pogoplug-series-4.dts
> ./arch/arm/boot/dts/omap5-uevm.dts
> ./arch/arm/boot/dts/ste-snowball.dts
Ah yes, I just grepped for 'debounce' in am* and omap*. I guess
that typo has been copied over from DT to DT. I'm tempted to spin
a patch correcting the typo, but I have no knowledge of those
boards or HW to test with. Obviously no-one has complained about
the 5ms vs 50ms debounce so far, so maybe 50ms isn't the correct
number in the first place?
> >
> > Not having seen any of that hardware, I can't say for certain what the
> > true HW requirements are. 1000ms does seem like a long debounce, perhaps
> > the author meant 1ms (1000us) for those buttons? Or perhaps it really
> > needs a 1000ms debounce, and is currently wrong?
> >
> >>
> >> But agree - max might not be a good choose, so can you add dev_err() below, pls.
> >
> > Given the above, I personally feel that a dev_err() is undesirable in most
> > cases. If I have a system and matching DT that just happens to need a longer
> > debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> > anything to be fixed.
> > I can understanding wanting to draw attention to a change in behavior (just
> > in case the DT is incorrect), but I'd personally lean towards dev_info() if
> > anything.
> >
> > That said: if you still prefer dev_err(), I will certainly do so.
>
> Fair enough :) thanks.
>
> Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Just to make sure I don't misunderstand, would you like me to:
A) put in a dev_err()
B) put in a dev_info()
C) leave it as-is without any message
?
I can spin a v2 as early as Monday, depending on the results of discussion
on the second patch.
>
> >
> > Tangent:
> > This discussion makes me think that adding a gpiod_get_max_debounce()
> > would allow even better behavior. Then asking for a too-high debounce
> > could be a dev_err() in all gpio drivers, with the expectation that no
> > driver should ask for such. Also, drivers could do something like use
> > max hardware debounce plus a software debounce for the remaining time,
> > in order to avoid CPU overhead on short glitches.
> >
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
2017-03-17 23:42 ` David Rivshin
(?)
@ 2017-04-20 14:44 ` David Rivshin
-1 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-04-20 14:44 UTC (permalink / raw)
To: Grygorii Strashko
Cc: linux-gpio, linux-omap, Santosh Shilimkar, Kevin Hilman,
Linus Walleij, Alexandre Courbot, linux-arm-kernel, linux-kernel,
stable
Hi Grygorii,
Not sure if you saw the question at the bottom asking for clarification
on what you'd prefer as far as any dev_xxx() message for this case. If
there is still concern on the other patch, I could just resubmit this
standalone (perhaps aiming for 4.12 at this point).
On Fri, 17 Mar 2017 19:42:35 -0400
David Rivshin <drivshin@awxrd.com> wrote:
> On Fri, 17 Mar 2017 16:43:56 -0500
> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>
> > On 03/17/2017 03:50 PM, David Rivshin wrote:
> > > On Fri, 17 Mar 2017 13:54:28 -0500
> > > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> > >
> > >> On 03/17/2017 12:54 PM, David Rivshin wrote:
> > >>> Hi Grygorii,
> > >>>
> > >>> On Fri, 17 Mar 2017 11:45:56 -0500
> > >>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> > >>>
> > >>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
> > >>>>> From: David Rivshin <DRivshin@allworx.com>
> > >>>>>
> > >>>>> omap_gpio_debounce() does not validate that the requested debounce
> > >>>>> is within a range it can handle. Instead it lets the register value
> > >>>>> wrap silently, and always returns success.
> > >>>>>
> > >>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> > >>>>> asking for a too-long debounce, but getting a very short debounce in
> > >>>>> practice.
> > >>>>>
> > >>>>> Fix this by returning -EINVAL if the requested value does not fit into
> > >>>>> the register field. If there is no debounce clock available at all,
> > >>>>> return -ENOTSUPP.
> > >>>>
> > >>>> In general this patch looks good, but there is one thing I'm worry about..
> > >>>>
> > >>>>>
> > >>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> > >>>>> Cc: <stable@vger.kernel.org> # 4.3+
> > >>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> > >>>>> ---
> > >>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> > >>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
> > >>>>>
> > >>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> > >>>>> index efc85a2..33ec02d 100644
> > >>>>> --- a/drivers/gpio/gpio-omap.c
> > >>>>> +++ b/drivers/gpio/gpio-omap.c
> > >>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> > >>>>> * OMAP's debounce time is in 31us steps
> > >>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> > >>>>> * so we need to convert and round up to the closest unit.
> > >>>>> + *
> > >>>>> + * Return: 0 on success, negative error otherwise.
> > >>>>> */
> > >>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> unsigned debounce)
> > >>>>> {
> > >>>>> void __iomem *reg;
> > >>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> bool enable = !!debounce;
> > >>>>>
> > >>>>> if (!bank->dbck_flag)
> > >>>>> - return;
> > >>>>> + return -ENOTSUPP;
> > >>>>>
> > >>>>> if (enable) {
> > >>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> > >>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> > >>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> > >>>>> + return -EINVAL;
> > >>>>
> > >>>> This might cause boot issues as current drivers may expect this op to succeed even if
> > >>>> configured value is wrong - just think, may be we can do warn here and use max value as
> > >>>> fallback?
> > >>>
> > >>> I have not looked through all drivers to be sure, but at least the gpio-keys
> > >>> driver requires set_debounce to return an error if it can't satisfy the request.
> > >>> In that case gpio-keys will use a software timer instead.
> > >>>
> > >>> if (button->debounce_interval) {
> > >>> error = gpiod_set_debounce(bdata->gpiod,
> > >>> button->debounce_interval * 1000);
> > >>> /* use timer if gpiolib doesn't provide debounce */
> > >>> if (error < 0)
> > >>> bdata->software_debounce =
> > >>> button->debounce_interval;
> > >>> }
> > >>>
> > >>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> > >>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> > >>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
> > >>> handle error returns gracefully.
> > >>>
> > >>> So I certainly understand the concern about backwards compatibility, but I
> > >>> think clipping to max is the greater of the evils in this case. Even a
> > >>> warning may be too much, because it's not necessarily anything wrong.
> > >>> Perhaps an info or debug message would be helpful, though?
> > >>>
> > >>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
> > >>> and see how they'd handle an error return. The handful I've looked through so
> > >>> far all behave like gpio-keys. The only ones I'd be particularly concerned
> > >>> about are platform-specific drivers which were perhaps never used with other
> > >>> gpio drivers. Do you know of that I should pay special attention to?
> > >>
> > >> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> > >> As result, even gpio-keys driver will just silently switch to software_debounce
> > >> without any notification.
> > >
> > > I think that switching to software_debounce silently is exactly the
> > > intended/desired behavior of gpio-keys (and other drivers). For example,
> > > if the DT requests a 20ms debounce on a gpio-key, the existing math
> > > resulted in a hardware debounce of just 2ms. With the error return,
> > > gpio-keys would silently switch to software_debounce of the requested
> > > 20ms (potentially longer if the CPU is busy, but I don't think that's
> > > a problem for correctness), exactly what the DT asked for.
> > >
[...snip...]
> > >>
> > >> But agree - max might not be a good choose, so can you add dev_err() below, pls.
> > >
> > > Given the above, I personally feel that a dev_err() is undesirable in most
> > > cases. If I have a system and matching DT that just happens to need a longer
> > > debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> > > anything to be fixed.
> > > I can understanding wanting to draw attention to a change in behavior (just
> > > in case the DT is incorrect), but I'd personally lean towards dev_info() if
> > > anything.
> > >
> > > That said: if you still prefer dev_err(), I will certainly do so.
> >
> > Fair enough :) thanks.
> >
> > Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
> Just to make sure I don't misunderstand, would you like me to:
> A) put in a dev_err()
> B) put in a dev_info()
> C) leave it as-is without any message
> ?
>
[...snip...]
FYI, I have searched for all uses of gpio{,d}_set_debounce (in v4.11-rc1),
and found nothing concerning. Most drivers fall back to software debounce.
The only exception I found was mmc_spi (via mmc_gpio_request_cd), but the
only time that has a non-zero debounce requested is for vision_ep9307 which
is hardcoded to ask for a 1us debounce via platform data. I don't believe
ep93xx would use the gpio-omap driver anyways. The mmc-spi-slot devicetree
binding doesn't support setting a debounce on any of the GPIOs.
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-04-20 14:44 ` David Rivshin
0 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-04-20 14:44 UTC (permalink / raw)
To: linux-arm-kernel
Hi Grygorii,
Not sure if you saw the question at the bottom asking for clarification
on what you'd prefer as far as any dev_xxx() message for this case. If
there is still concern on the other patch, I could just resubmit this
standalone (perhaps aiming for 4.12 at this point).
On Fri, 17 Mar 2017 19:42:35 -0400
David Rivshin <drivshin@awxrd.com> wrote:
> On Fri, 17 Mar 2017 16:43:56 -0500
> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>
> > On 03/17/2017 03:50 PM, David Rivshin wrote:
> > > On Fri, 17 Mar 2017 13:54:28 -0500
> > > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> > >
> > >> On 03/17/2017 12:54 PM, David Rivshin wrote:
> > >>> Hi Grygorii,
> > >>>
> > >>> On Fri, 17 Mar 2017 11:45:56 -0500
> > >>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> > >>>
> > >>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
> > >>>>> From: David Rivshin <DRivshin@allworx.com>
> > >>>>>
> > >>>>> omap_gpio_debounce() does not validate that the requested debounce
> > >>>>> is within a range it can handle. Instead it lets the register value
> > >>>>> wrap silently, and always returns success.
> > >>>>>
> > >>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> > >>>>> asking for a too-long debounce, but getting a very short debounce in
> > >>>>> practice.
> > >>>>>
> > >>>>> Fix this by returning -EINVAL if the requested value does not fit into
> > >>>>> the register field. If there is no debounce clock available at all,
> > >>>>> return -ENOTSUPP.
> > >>>>
> > >>>> In general this patch looks good, but there is one thing I'm worry about..
> > >>>>
> > >>>>>
> > >>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> > >>>>> Cc: <stable@vger.kernel.org> # 4.3+
> > >>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> > >>>>> ---
> > >>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> > >>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
> > >>>>>
> > >>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> > >>>>> index efc85a2..33ec02d 100644
> > >>>>> --- a/drivers/gpio/gpio-omap.c
> > >>>>> +++ b/drivers/gpio/gpio-omap.c
> > >>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> > >>>>> * OMAP's debounce time is in 31us steps
> > >>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> > >>>>> * so we need to convert and round up to the closest unit.
> > >>>>> + *
> > >>>>> + * Return: 0 on success, negative error otherwise.
> > >>>>> */
> > >>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> unsigned debounce)
> > >>>>> {
> > >>>>> void __iomem *reg;
> > >>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> bool enable = !!debounce;
> > >>>>>
> > >>>>> if (!bank->dbck_flag)
> > >>>>> - return;
> > >>>>> + return -ENOTSUPP;
> > >>>>>
> > >>>>> if (enable) {
> > >>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> > >>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> > >>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> > >>>>> + return -EINVAL;
> > >>>>
> > >>>> This might cause boot issues as current drivers may expect this op to succeed even if
> > >>>> configured value is wrong - just think, may be we can do warn here and use max value as
> > >>>> fallback?
> > >>>
> > >>> I have not looked through all drivers to be sure, but at least the gpio-keys
> > >>> driver requires set_debounce to return an error if it can't satisfy the request.
> > >>> In that case gpio-keys will use a software timer instead.
> > >>>
> > >>> if (button->debounce_interval) {
> > >>> error = gpiod_set_debounce(bdata->gpiod,
> > >>> button->debounce_interval * 1000);
> > >>> /* use timer if gpiolib doesn't provide debounce */
> > >>> if (error < 0)
> > >>> bdata->software_debounce =
> > >>> button->debounce_interval;
> > >>> }
> > >>>
> > >>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> > >>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> > >>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
> > >>> handle error returns gracefully.
> > >>>
> > >>> So I certainly understand the concern about backwards compatibility, but I
> > >>> think clipping to max is the greater of the evils in this case. Even a
> > >>> warning may be too much, because it's not necessarily anything wrong.
> > >>> Perhaps an info or debug message would be helpful, though?
> > >>>
> > >>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
> > >>> and see how they'd handle an error return. The handful I've looked through so
> > >>> far all behave like gpio-keys. The only ones I'd be particularly concerned
> > >>> about are platform-specific drivers which were perhaps never used with other
> > >>> gpio drivers. Do you know of that I should pay special attention to?
> > >>
> > >> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> > >> As result, even gpio-keys driver will just silently switch to software_debounce
> > >> without any notification.
> > >
> > > I think that switching to software_debounce silently is exactly the
> > > intended/desired behavior of gpio-keys (and other drivers). For example,
> > > if the DT requests a 20ms debounce on a gpio-key, the existing math
> > > resulted in a hardware debounce of just 2ms. With the error return,
> > > gpio-keys would silently switch to software_debounce of the requested
> > > 20ms (potentially longer if the CPU is busy, but I don't think that's
> > > a problem for correctness), exactly what the DT asked for.
> > >
[...snip...]
> > >>
> > >> But agree - max might not be a good choose, so can you add dev_err() below, pls.
> > >
> > > Given the above, I personally feel that a dev_err() is undesirable in most
> > > cases. If I have a system and matching DT that just happens to need a longer
> > > debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> > > anything to be fixed.
> > > I can understanding wanting to draw attention to a change in behavior (just
> > > in case the DT is incorrect), but I'd personally lean towards dev_info() if
> > > anything.
> > >
> > > That said: if you still prefer dev_err(), I will certainly do so.
> >
> > Fair enough :) thanks.
> >
> > Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
> Just to make sure I don't misunderstand, would you like me to:
> A) put in a dev_err()
> B) put in a dev_info()
> C) leave it as-is without any message
> ?
>
[...snip...]
FYI, I have searched for all uses of gpio{,d}_set_debounce (in v4.11-rc1),
and found nothing concerning. Most drivers fall back to software debounce.
The only exception I found was mmc_spi (via mmc_gpio_request_cd), but the
only time that has a non-zero debounce requested is for vision_ep9307 which
is hardcoded to ask for a 1us debounce via platform data. I don't believe
ep93xx would use the gpio-omap driver anyways. The mmc-spi-slot devicetree
binding doesn't support setting a debounce on any of the GPIOs.
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-04-20 14:44 ` David Rivshin
0 siblings, 0 replies; 35+ messages in thread
From: David Rivshin @ 2017-04-20 14:44 UTC (permalink / raw)
To: Grygorii Strashko
Cc: linux-gpio, linux-omap, Santosh Shilimkar, Kevin Hilman,
Linus Walleij, Alexandre Courbot, linux-arm-kernel, linux-kernel,
stable
Hi Grygorii,
Not sure if you saw the question at the bottom asking for clarification
on what you'd prefer as far as any dev_xxx() message for this case. If
there is still concern on the other patch, I could just resubmit this
standalone (perhaps aiming for 4.12 at this point).
On Fri, 17 Mar 2017 19:42:35 -0400
David Rivshin <drivshin@awxrd.com> wrote:
> On Fri, 17 Mar 2017 16:43:56 -0500
> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>
> > On 03/17/2017 03:50 PM, David Rivshin wrote:
> > > On Fri, 17 Mar 2017 13:54:28 -0500
> > > Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> > >
> > >> On 03/17/2017 12:54 PM, David Rivshin wrote:
> > >>> Hi Grygorii,
> > >>>
> > >>> On Fri, 17 Mar 2017 11:45:56 -0500
> > >>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
> > >>>
> > >>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
> > >>>>> From: David Rivshin <DRivshin@allworx.com>
> > >>>>>
> > >>>>> omap_gpio_debounce() does not validate that the requested debounce
> > >>>>> is within a range it can handle. Instead it lets the register value
> > >>>>> wrap silently, and always returns success.
> > >>>>>
> > >>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
> > >>>>> asking for a too-long debounce, but getting a very short debounce in
> > >>>>> practice.
> > >>>>>
> > >>>>> Fix this by returning -EINVAL if the requested value does not fit into
> > >>>>> the register field. If there is no debounce clock available at all,
> > >>>>> return -ENOTSUPP.
> > >>>>
> > >>>> In general this patch looks good, but there is one thing I'm worry about..
> > >>>>
> > >>>>>
> > >>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> > >>>>> Cc: <stable@vger.kernel.org> # 4.3+
> > >>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
> > >>>>> ---
> > >>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> > >>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
> > >>>>>
> > >>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> > >>>>> index efc85a2..33ec02d 100644
> > >>>>> --- a/drivers/gpio/gpio-omap.c
> > >>>>> +++ b/drivers/gpio/gpio-omap.c
> > >>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> > >>>>> * OMAP's debounce time is in 31us steps
> > >>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> > >>>>> * so we need to convert and round up to the closest unit.
> > >>>>> + *
> > >>>>> + * Return: 0 on success, negative error otherwise.
> > >>>>> */
> > >>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> unsigned debounce)
> > >>>>> {
> > >>>>> void __iomem *reg;
> > >>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> > >>>>> bool enable = !!debounce;
> > >>>>>
> > >>>>> if (!bank->dbck_flag)
> > >>>>> - return;
> > >>>>> + return -ENOTSUPP;
> > >>>>>
> > >>>>> if (enable) {
> > >>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> > >>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> > >>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> > >>>>> + return -EINVAL;
> > >>>>
> > >>>> This might cause boot issues as current drivers may expect this op to succeed even if
> > >>>> configured value is wrong - just think, may be we can do warn here and use max value as
> > >>>> fallback?
> > >>>
> > >>> I have not looked through all drivers to be sure, but at least the gpio-keys
> > >>> driver requires set_debounce to return an error if it can't satisfy the request.
> > >>> In that case gpio-keys will use a software timer instead.
> > >>>
> > >>> if (button->debounce_interval) {
> > >>> error = gpiod_set_debounce(bdata->gpiod,
> > >>> button->debounce_interval * 1000);
> > >>> /* use timer if gpiolib doesn't provide debounce */
> > >>> if (error < 0)
> > >>> bdata->software_debounce =
> > >>> button->debounce_interval;
> > >>> }
> > >>>
> > >>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
> > >>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
> > >>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
> > >>> handle error returns gracefully.
> > >>>
> > >>> So I certainly understand the concern about backwards compatibility, but I
> > >>> think clipping to max is the greater of the evils in this case. Even a
> > >>> warning may be too much, because it's not necessarily anything wrong.
> > >>> Perhaps an info or debug message would be helpful, though?
> > >>>
> > >>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
> > >>> and see how they'd handle an error return. The handful I've looked through so
> > >>> far all behave like gpio-keys. The only ones I'd be particularly concerned
> > >>> about are platform-specific drivers which were perhaps never used with other
> > >>> gpio drivers. Do you know of that I should pay special attention to?
> > >>
> > >> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
> > >> As result, even gpio-keys driver will just silently switch to software_debounce
> > >> without any notification.
> > >
> > > I think that switching to software_debounce silently is exactly the
> > > intended/desired behavior of gpio-keys (and other drivers). For example,
> > > if the DT requests a 20ms debounce on a gpio-key, the existing math
> > > resulted in a hardware debounce of just 2ms. With the error return,
> > > gpio-keys would silently switch to software_debounce of the requested
> > > 20ms (potentially longer if the CPU is busy, but I don't think that's
> > > a problem for correctness), exactly what the DT asked for.
> > >
[...snip...]
> > >>
> > >> But agree - max might not be a good choose, so can you add dev_err() below, pls.
> > >
> > > Given the above, I personally feel that a dev_err() is undesirable in most
> > > cases. If I have a system and matching DT that just happens to need a longer
> > > debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
> > > anything to be fixed.
> > > I can understanding wanting to draw attention to a change in behavior (just
> > > in case the DT is incorrect), but I'd personally lean towards dev_info() if
> > > anything.
> > >
> > > That said: if you still prefer dev_err(), I will certainly do so.
> >
> > Fair enough :) thanks.
> >
> > Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
> Just to make sure I don't misunderstand, would you like me to:
> A) put in a dev_err()
> B) put in a dev_info()
> C) leave it as-is without any message
> ?
>
[...snip...]
FYI, I have searched for all uses of gpio{,d}_set_debounce (in v4.11-rc1),
and found nothing concerning. Most drivers fall back to software debounce.
The only exception I found was mmc_spi (via mmc_gpio_request_cd), but the
only time that has a non-zero debounce requested is for vision_ep9307 which
is hardcoded to ask for a 1us debounce via platform data. I don't believe
ep93xx would use the gpio-omap driver anyways. The mmc-spi-slot devicetree
binding doesn't support setting a debounce on any of the GPIOs.
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
2017-04-20 14:44 ` David Rivshin
(?)
@ 2017-04-20 15:19 ` Grygorii Strashko
-1 siblings, 0 replies; 35+ messages in thread
From: Grygorii Strashko @ 2017-04-20 15:19 UTC (permalink / raw)
To: David Rivshin
Cc: Alexandre Courbot, Kevin Hilman, Linus Walleij, linux-kernel,
stable, linux-gpio, Santosh Shilimkar, linux-omap,
linux-arm-kernel
On 04/20/2017 09:44 AM, David Rivshin wrote:
> Hi Grygorii,
>
> Not sure if you saw the question at the bottom asking for clarification
> on what you'd prefer as far as any dev_xxx() message for this case. If
> there is still concern on the other patch, I could just resubmit this
> standalone (perhaps aiming for 4.12 at this point).
Could you add dev info and resubmit this alone, pls
>
> On Fri, 17 Mar 2017 19:42:35 -0400
> David Rivshin <drivshin@awxrd.com> wrote:
>
>> On Fri, 17 Mar 2017 16:43:56 -0500
>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>
>>> On 03/17/2017 03:50 PM, David Rivshin wrote:
>>>> On Fri, 17 Mar 2017 13:54:28 -0500
>>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>>
>>>>> On 03/17/2017 12:54 PM, David Rivshin wrote:
>>>>>> Hi Grygorii,
>>>>>>
>>>>>> On Fri, 17 Mar 2017 11:45:56 -0500
>>>>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>>>>
>>>>>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
>>>>>>>> From: David Rivshin <DRivshin@allworx.com>
>>>>>>>>
>>>>>>>> omap_gpio_debounce() does not validate that the requested debounce
>>>>>>>> is within a range it can handle. Instead it lets the register value
>>>>>>>> wrap silently, and always returns success.
>>>>>>>>
>>>>>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
>>>>>>>> asking for a too-long debounce, but getting a very short debounce in
>>>>>>>> practice.
>>>>>>>>
>>>>>>>> Fix this by returning -EINVAL if the requested value does not fit into
>>>>>>>> the register field. If there is no debounce clock available at all,
>>>>>>>> return -ENOTSUPP.
>>>>>>>
>>>>>>> In general this patch looks good, but there is one thing I'm worry about..
>>>>>>>
>>>>>>>>
>>>>>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
>>>>>>>> Cc: <stable@vger.kernel.org> # 4.3+
>>>>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>>>>> ---
>>>>>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
>>>>>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>>>>>> index efc85a2..33ec02d 100644
>>>>>>>> --- a/drivers/gpio/gpio-omap.c
>>>>>>>> +++ b/drivers/gpio/gpio-omap.c
>>>>>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
>>>>>>>> * OMAP's debounce time is in 31us steps
>>>>>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
>>>>>>>> * so we need to convert and round up to the closest unit.
>>>>>>>> + *
>>>>>>>> + * Return: 0 on success, negative error otherwise.
>>>>>>>> */
>>>>>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> unsigned debounce)
>>>>>>>> {
>>>>>>>> void __iomem *reg;
>>>>>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> bool enable = !!debounce;
>>>>>>>>
>>>>>>>> if (!bank->dbck_flag)
>>>>>>>> - return;
>>>>>>>> + return -ENOTSUPP;
>>>>>>>>
>>>>>>>> if (enable) {
>>>>>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
>>>>>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
>>>>>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
>>>>>>>> + return -EINVAL;
>>>>>>>
>>>>>>> This might cause boot issues as current drivers may expect this op to succeed even if
>>>>>>> configured value is wrong - just think, may be we can do warn here and use max value as
>>>>>>> fallback?
>>>>>>
>>>>>> I have not looked through all drivers to be sure, but at least the gpio-keys
>>>>>> driver requires set_debounce to return an error if it can't satisfy the request.
>>>>>> In that case gpio-keys will use a software timer instead.
>>>>>>
>>>>>> if (button->debounce_interval) {
>>>>>> error = gpiod_set_debounce(bdata->gpiod,
>>>>>> button->debounce_interval * 1000);
>>>>>> /* use timer if gpiolib doesn't provide debounce */
>>>>>> if (error < 0)
>>>>>> bdata->software_debounce =
>>>>>> button->debounce_interval;
>>>>>> }
>>>>>>
>>>>>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
>>>>>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
>>>>>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
>>>>>> handle error returns gracefully.
>>>>>>
>>>>>> So I certainly understand the concern about backwards compatibility, but I
>>>>>> think clipping to max is the greater of the evils in this case. Even a
>>>>>> warning may be too much, because it's not necessarily anything wrong.
>>>>>> Perhaps an info or debug message would be helpful, though?
>>>>>>
>>>>>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
>>>>>> and see how they'd handle an error return. The handful I've looked through so
>>>>>> far all behave like gpio-keys. The only ones I'd be particularly concerned
>>>>>> about are platform-specific drivers which were perhaps never used with other
>>>>>> gpio drivers. Do you know of that I should pay special attention to?
>>>>>
>>>>> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
>>>>> As result, even gpio-keys driver will just silently switch to software_debounce
>>>>> without any notification.
>>>>
>>>> I think that switching to software_debounce silently is exactly the
>>>> intended/desired behavior of gpio-keys (and other drivers). For example,
>>>> if the DT requests a 20ms debounce on a gpio-key, the existing math
>>>> resulted in a hardware debounce of just 2ms. With the error return,
>>>> gpio-keys would silently switch to software_debounce of the requested
>>>> 20ms (potentially longer if the CPU is busy, but I don't think that's
>>>> a problem for correctness), exactly what the DT asked for.
>>>>
> [...snip...]
>>>>>
>>>>> But agree - max might not be a good choose, so can you add dev_err() below, pls.
>>>>
>>>> Given the above, I personally feel that a dev_err() is undesirable in most
>>>> cases. If I have a system and matching DT that just happens to need a longer
>>>> debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
>>>> anything to be fixed.
>>>> I can understanding wanting to draw attention to a change in behavior (just
>>>> in case the DT is incorrect), but I'd personally lean towards dev_info() if
>>>> anything.
>>>>
>>>> That said: if you still prefer dev_err(), I will certainly do so.
>>>
>>> Fair enough :) thanks.
>>>
>>> Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>
>> Just to make sure I don't misunderstand, would you like me to:
>> A) put in a dev_err()
>> B) put in a dev_info()
>> C) leave it as-is without any message
>> ?
>>
> [...snip...]
>
> FYI, I have searched for all uses of gpio{,d}_set_debounce (in v4.11-rc1),
> and found nothing concerning. Most drivers fall back to software debounce.
>
> The only exception I found was mmc_spi (via mmc_gpio_request_cd), but the
> only time that has a non-zero debounce requested is for vision_ep9307 which
> is hardcoded to ask for a 1us debounce via platform data. I don't believe
> ep93xx would use the gpio-omap driver anyways. The mmc-spi-slot devicetree
> binding doesn't support setting a debounce on any of the GPIOs.
>
--
regards,
-grygorii
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-04-20 15:19 ` Grygorii Strashko
0 siblings, 0 replies; 35+ messages in thread
From: Grygorii Strashko @ 2017-04-20 15:19 UTC (permalink / raw)
To: linux-arm-kernel
On 04/20/2017 09:44 AM, David Rivshin wrote:
> Hi Grygorii,
>
> Not sure if you saw the question at the bottom asking for clarification
> on what you'd prefer as far as any dev_xxx() message for this case. If
> there is still concern on the other patch, I could just resubmit this
> standalone (perhaps aiming for 4.12 at this point).
Could you add dev info and resubmit this alone, pls
>
> On Fri, 17 Mar 2017 19:42:35 -0400
> David Rivshin <drivshin@awxrd.com> wrote:
>
>> On Fri, 17 Mar 2017 16:43:56 -0500
>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>
>>> On 03/17/2017 03:50 PM, David Rivshin wrote:
>>>> On Fri, 17 Mar 2017 13:54:28 -0500
>>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>>
>>>>> On 03/17/2017 12:54 PM, David Rivshin wrote:
>>>>>> Hi Grygorii,
>>>>>>
>>>>>> On Fri, 17 Mar 2017 11:45:56 -0500
>>>>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>>>>
>>>>>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
>>>>>>>> From: David Rivshin <DRivshin@allworx.com>
>>>>>>>>
>>>>>>>> omap_gpio_debounce() does not validate that the requested debounce
>>>>>>>> is within a range it can handle. Instead it lets the register value
>>>>>>>> wrap silently, and always returns success.
>>>>>>>>
>>>>>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
>>>>>>>> asking for a too-long debounce, but getting a very short debounce in
>>>>>>>> practice.
>>>>>>>>
>>>>>>>> Fix this by returning -EINVAL if the requested value does not fit into
>>>>>>>> the register field. If there is no debounce clock available at all,
>>>>>>>> return -ENOTSUPP.
>>>>>>>
>>>>>>> In general this patch looks good, but there is one thing I'm worry about..
>>>>>>>
>>>>>>>>
>>>>>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
>>>>>>>> Cc: <stable@vger.kernel.org> # 4.3+
>>>>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>>>>> ---
>>>>>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
>>>>>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>>>>>> index efc85a2..33ec02d 100644
>>>>>>>> --- a/drivers/gpio/gpio-omap.c
>>>>>>>> +++ b/drivers/gpio/gpio-omap.c
>>>>>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
>>>>>>>> * OMAP's debounce time is in 31us steps
>>>>>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
>>>>>>>> * so we need to convert and round up to the closest unit.
>>>>>>>> + *
>>>>>>>> + * Return: 0 on success, negative error otherwise.
>>>>>>>> */
>>>>>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> unsigned debounce)
>>>>>>>> {
>>>>>>>> void __iomem *reg;
>>>>>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> bool enable = !!debounce;
>>>>>>>>
>>>>>>>> if (!bank->dbck_flag)
>>>>>>>> - return;
>>>>>>>> + return -ENOTSUPP;
>>>>>>>>
>>>>>>>> if (enable) {
>>>>>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
>>>>>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
>>>>>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
>>>>>>>> + return -EINVAL;
>>>>>>>
>>>>>>> This might cause boot issues as current drivers may expect this op to succeed even if
>>>>>>> configured value is wrong - just think, may be we can do warn here and use max value as
>>>>>>> fallback?
>>>>>>
>>>>>> I have not looked through all drivers to be sure, but at least the gpio-keys
>>>>>> driver requires set_debounce to return an error if it can't satisfy the request.
>>>>>> In that case gpio-keys will use a software timer instead.
>>>>>>
>>>>>> if (button->debounce_interval) {
>>>>>> error = gpiod_set_debounce(bdata->gpiod,
>>>>>> button->debounce_interval * 1000);
>>>>>> /* use timer if gpiolib doesn't provide debounce */
>>>>>> if (error < 0)
>>>>>> bdata->software_debounce =
>>>>>> button->debounce_interval;
>>>>>> }
>>>>>>
>>>>>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
>>>>>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
>>>>>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
>>>>>> handle error returns gracefully.
>>>>>>
>>>>>> So I certainly understand the concern about backwards compatibility, but I
>>>>>> think clipping to max is the greater of the evils in this case. Even a
>>>>>> warning may be too much, because it's not necessarily anything wrong.
>>>>>> Perhaps an info or debug message would be helpful, though?
>>>>>>
>>>>>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
>>>>>> and see how they'd handle an error return. The handful I've looked through so
>>>>>> far all behave like gpio-keys. The only ones I'd be particularly concerned
>>>>>> about are platform-specific drivers which were perhaps never used with other
>>>>>> gpio drivers. Do you know of that I should pay special attention to?
>>>>>
>>>>> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
>>>>> As result, even gpio-keys driver will just silently switch to software_debounce
>>>>> without any notification.
>>>>
>>>> I think that switching to software_debounce silently is exactly the
>>>> intended/desired behavior of gpio-keys (and other drivers). For example,
>>>> if the DT requests a 20ms debounce on a gpio-key, the existing math
>>>> resulted in a hardware debounce of just 2ms. With the error return,
>>>> gpio-keys would silently switch to software_debounce of the requested
>>>> 20ms (potentially longer if the CPU is busy, but I don't think that's
>>>> a problem for correctness), exactly what the DT asked for.
>>>>
> [...snip...]
>>>>>
>>>>> But agree - max might not be a good choose, so can you add dev_err() below, pls.
>>>>
>>>> Given the above, I personally feel that a dev_err() is undesirable in most
>>>> cases. If I have a system and matching DT that just happens to need a longer
>>>> debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
>>>> anything to be fixed.
>>>> I can understanding wanting to draw attention to a change in behavior (just
>>>> in case the DT is incorrect), but I'd personally lean towards dev_info() if
>>>> anything.
>>>>
>>>> That said: if you still prefer dev_err(), I will certainly do so.
>>>
>>> Fair enough :) thanks.
>>>
>>> Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>
>> Just to make sure I don't misunderstand, would you like me to:
>> A) put in a dev_err()
>> B) put in a dev_info()
>> C) leave it as-is without any message
>> ?
>>
> [...snip...]
>
> FYI, I have searched for all uses of gpio{,d}_set_debounce (in v4.11-rc1),
> and found nothing concerning. Most drivers fall back to software debounce.
>
> The only exception I found was mmc_spi (via mmc_gpio_request_cd), but the
> only time that has a non-zero debounce requested is for vision_ep9307 which
> is hardcoded to ask for a 1us debounce via platform data. I don't believe
> ep93xx would use the gpio-omap driver anyways. The mmc-spi-slot devicetree
> binding doesn't support setting a debounce on any of the GPIOs.
>
--
regards,
-grygorii
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH 1/2] gpio: omap: return error if requested debounce time is not possible
@ 2017-04-20 15:19 ` Grygorii Strashko
0 siblings, 0 replies; 35+ messages in thread
From: Grygorii Strashko @ 2017-04-20 15:19 UTC (permalink / raw)
To: David Rivshin
Cc: linux-gpio, linux-omap, Santosh Shilimkar, Kevin Hilman,
Linus Walleij, Alexandre Courbot, linux-arm-kernel, linux-kernel,
stable
On 04/20/2017 09:44 AM, David Rivshin wrote:
> Hi Grygorii,
>
> Not sure if you saw the question at the bottom asking for clarification
> on what you'd prefer as far as any dev_xxx() message for this case. If
> there is still concern on the other patch, I could just resubmit this
> standalone (perhaps aiming for 4.12 at this point).
Could you add dev info and resubmit this alone, pls
>
> On Fri, 17 Mar 2017 19:42:35 -0400
> David Rivshin <drivshin@awxrd.com> wrote:
>
>> On Fri, 17 Mar 2017 16:43:56 -0500
>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>
>>> On 03/17/2017 03:50 PM, David Rivshin wrote:
>>>> On Fri, 17 Mar 2017 13:54:28 -0500
>>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>>
>>>>> On 03/17/2017 12:54 PM, David Rivshin wrote:
>>>>>> Hi Grygorii,
>>>>>>
>>>>>> On Fri, 17 Mar 2017 11:45:56 -0500
>>>>>> Grygorii Strashko <grygorii.strashko@ti.com> wrote:
>>>>>>
>>>>>>> On 03/16/2017 07:57 PM, David Rivshin wrote:
>>>>>>>> From: David Rivshin <DRivshin@allworx.com>
>>>>>>>>
>>>>>>>> omap_gpio_debounce() does not validate that the requested debounce
>>>>>>>> is within a range it can handle. Instead it lets the register value
>>>>>>>> wrap silently, and always returns success.
>>>>>>>>
>>>>>>>> This can lead to all sorts of unexpected behavior, such as gpio_keys
>>>>>>>> asking for a too-long debounce, but getting a very short debounce in
>>>>>>>> practice.
>>>>>>>>
>>>>>>>> Fix this by returning -EINVAL if the requested value does not fit into
>>>>>>>> the register field. If there is no debounce clock available at all,
>>>>>>>> return -ENOTSUPP.
>>>>>>>
>>>>>>> In general this patch looks good, but there is one thing I'm worry about..
>>>>>>>
>>>>>>>>
>>>>>>>> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
>>>>>>>> Cc: <stable@vger.kernel.org> # 4.3+
>>>>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>>>>> ---
>>>>>>>> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
>>>>>>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>>>>>> index efc85a2..33ec02d 100644
>>>>>>>> --- a/drivers/gpio/gpio-omap.c
>>>>>>>> +++ b/drivers/gpio/gpio-omap.c
>>>>>>>> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
>>>>>>>> * OMAP's debounce time is in 31us steps
>>>>>>>> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
>>>>>>>> * so we need to convert and round up to the closest unit.
>>>>>>>> + *
>>>>>>>> + * Return: 0 on success, negative error otherwise.
>>>>>>>> */
>>>>>>>> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> unsigned debounce)
>>>>>>>> {
>>>>>>>> void __iomem *reg;
>>>>>>>> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
>>>>>>>> bool enable = !!debounce;
>>>>>>>>
>>>>>>>> if (!bank->dbck_flag)
>>>>>>>> - return;
>>>>>>>> + return -ENOTSUPP;
>>>>>>>>
>>>>>>>> if (enable) {
>>>>>>>> debounce = DIV_ROUND_UP(debounce, 31) - 1;
>>>>>>>> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
>>>>>>>> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
>>>>>>>> + return -EINVAL;
>>>>>>>
>>>>>>> This might cause boot issues as current drivers may expect this op to succeed even if
>>>>>>> configured value is wrong - just think, may be we can do warn here and use max value as
>>>>>>> fallback?
>>>>>>
>>>>>> I have not looked through all drivers to be sure, but at least the gpio-keys
>>>>>> driver requires set_debounce to return an error if it can't satisfy the request.
>>>>>> In that case gpio-keys will use a software timer instead.
>>>>>>
>>>>>> if (button->debounce_interval) {
>>>>>> error = gpiod_set_debounce(bdata->gpiod,
>>>>>> button->debounce_interval * 1000);
>>>>>> /* use timer if gpiolib doesn't provide debounce */
>>>>>> if (error < 0)
>>>>>> bdata->software_debounce =
>>>>>> button->debounce_interval;
>>>>>> }
>>>>>>
>>>>>> Also, at least some other GPIO drivers (e.g. gpio-max7760) return -EINVAL in
>>>>>> such a case. And gpiolib will return -ENOTSUPP if there is no debounce
>>>>>> callback at all. So I expect all drivers which use gpiod_set_debounce() to
>>>>>> handle error returns gracefully.
>>>>>>
>>>>>> So I certainly understand the concern about backwards compatibility, but I
>>>>>> think clipping to max is the greater of the evils in this case. Even a
>>>>>> warning may be too much, because it's not necessarily anything wrong.
>>>>>> Perhaps an info or debug message would be helpful, though?
>>>>>>
>>>>>> If you prefer, I can try to go through all callers of gpiod_set_debounce()
>>>>>> and see how they'd handle an error return. The handful I've looked through so
>>>>>> far all behave like gpio-keys. The only ones I'd be particularly concerned
>>>>>> about are platform-specific drivers which were perhaps never used with other
>>>>>> gpio drivers. Do you know of that I should pay special attention to?
>>>>>
>>>>> Yeh agree. But the problem here will be not only with drivers itself - it can be wrong data in DT :(
>>>>> As result, even gpio-keys driver will just silently switch to software_debounce
>>>>> without any notification.
>>>>
>>>> I think that switching to software_debounce silently is exactly the
>>>> intended/desired behavior of gpio-keys (and other drivers). For example,
>>>> if the DT requests a 20ms debounce on a gpio-key, the existing math
>>>> resulted in a hardware debounce of just 2ms. With the error return,
>>>> gpio-keys would silently switch to software_debounce of the requested
>>>> 20ms (potentially longer if the CPU is busy, but I don't think that's
>>>> a problem for correctness), exactly what the DT asked for.
>>>>
> [...snip...]
>>>>>
>>>>> But agree - max might not be a good choose, so can you add dev_err() below, pls.
>>>>
>>>> Given the above, I personally feel that a dev_err() is undesirable in most
>>>> cases. If I have a system and matching DT that just happens to need a longer
>>>> debounce than the GPIO HW is capable of, gpio-keys (etc) does the best it can automatically. I don't consider that there is any error in that case, or
>>>> anything to be fixed.
>>>> I can understanding wanting to draw attention to a change in behavior (just
>>>> in case the DT is incorrect), but I'd personally lean towards dev_info() if
>>>> anything.
>>>>
>>>> That said: if you still prefer dev_err(), I will certainly do so.
>>>
>>> Fair enough :) thanks.
>>>
>>> Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>
>> Just to make sure I don't misunderstand, would you like me to:
>> A) put in a dev_err()
>> B) put in a dev_info()
>> C) leave it as-is without any message
>> ?
>>
> [...snip...]
>
> FYI, I have searched for all uses of gpio{,d}_set_debounce (in v4.11-rc1),
> and found nothing concerning. Most drivers fall back to software debounce.
>
> The only exception I found was mmc_spi (via mmc_gpio_request_cd), but the
> only time that has a non-zero debounce requested is for vision_ep9307 which
> is hardcoded to ask for a 1us debounce via platform data. I don't believe
> ep93xx would use the gpio-omap driver anyways. The mmc-spi-slot devicetree
> binding doesn't support setting a debounce on any of the GPIOs.
>
--
regards,
-grygorii
^ permalink raw reply [flat|nested] 35+ messages in thread