* [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
@ 2021-04-01 21:45 Konstantin Aladyshev
2021-04-05 21:41 ` Guenter Roeck
0 siblings, 1 reply; 9+ messages in thread
From: Konstantin Aladyshev @ 2021-04-01 21:45 UTC (permalink / raw)
Cc: kunyi, aladyshev22, Konstantin Aladyshev, Jean Delvare,
Guenter Roeck, linux-hwmon, linux-kernel
From: Konstantin Aladyshev <aladyshev@nicevt.ru>
SBTSI sensors don't work when the CPU is off.
In this case every 'i2c_smbus_read_byte_data' function would fail
by a timeout.
Currently temp1_max/temp1_min file reads can cause two such timeouts
for every read.
Restructure code so there will be no more than one timeout for every
read opeartion.
Signed-off-by: Konstantin Aladyshev <aladyshev@nicevt.ru>
---
drivers/hwmon/sbtsi_temp.c | 59 +++++++++++++++++++-------------------
1 file changed, 29 insertions(+), 30 deletions(-)
diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
index e35357c48b8e..e09a8cf6de45 100644
--- a/drivers/hwmon/sbtsi_temp.c
+++ b/drivers/hwmon/sbtsi_temp.c
@@ -74,53 +74,52 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long *val)
{
struct sbtsi_data *data = dev_get_drvdata(dev);
+ u8 temp_int_reg, temp_dec_reg;
s32 temp_int, temp_dec;
int err;
switch (attr) {
case hwmon_temp_input:
- /*
- * ReadOrder bit specifies the reading order of integer and
- * decimal part of CPU temp for atomic reads. If bit == 0,
- * reading integer part triggers latching of the decimal part,
- * so integer part should be read first. If bit == 1, read
- * order should be reversed.
- */
- err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
- if (err < 0)
- return err;
-
- mutex_lock(&data->lock);
- if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
- } else {
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
- }
- mutex_unlock(&data->lock);
+ temp_int_reg = SBTSI_REG_TEMP_INT;
+ temp_dec_reg = SBTSI_REG_TEMP_DEC;
break;
case hwmon_temp_max:
- mutex_lock(&data->lock);
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
- mutex_unlock(&data->lock);
+ temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
+ temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
break;
case hwmon_temp_min:
- mutex_lock(&data->lock);
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
- mutex_unlock(&data->lock);
+ temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
+ temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
break;
default:
return -EINVAL;
}
+ /*
+ * ReadOrder bit specifies the reading order of integer and
+ * decimal part of CPU temp for atomic reads. If bit == 0,
+ * reading integer part triggers latching of the decimal part,
+ * so integer part should be read first. If bit == 1, read
+ * order should be reversed.
+ */
+ err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
+ if (err < 0)
+ return err;
+
+ mutex_lock(&data->lock);
+ if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
+ temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
+ temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
+ } else {
+ temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
+ temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
+ }
+ mutex_unlock(&data->lock);
- if (temp_int < 0)
- return temp_int;
if (temp_dec < 0)
return temp_dec;
+ if (temp_int < 0)
+ return temp_int;
*val = sbtsi_reg_to_mc(temp_int, temp_dec);
--
2.17.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-01 21:45 [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond Konstantin Aladyshev
@ 2021-04-05 21:41 ` Guenter Roeck
2021-04-06 18:16 ` [PATCH v2] " Konstantin Aladyshev
0 siblings, 1 reply; 9+ messages in thread
From: Guenter Roeck @ 2021-04-05 21:41 UTC (permalink / raw)
To: Konstantin Aladyshev
Cc: kunyi, Konstantin Aladyshev, Jean Delvare, linux-hwmon, linux-kernel
On 4/1/21 2:45 PM, Konstantin Aladyshev wrote:
> From: Konstantin Aladyshev <aladyshev@nicevt.ru>
>
> SBTSI sensors don't work when the CPU is off.
> In this case every 'i2c_smbus_read_byte_data' function would fail
> by a timeout.
> Currently temp1_max/temp1_min file reads can cause two such timeouts
> for every read.
> Restructure code so there will be no more than one timeout for every
> read opeartion.
>
operation
> Signed-off-by: Konstantin Aladyshev <aladyshev@nicevt.ru>
> ---
> drivers/hwmon/sbtsi_temp.c | 59 +++++++++++++++++++-------------------
> 1 file changed, 29 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
> index e35357c48b8e..e09a8cf6de45 100644
> --- a/drivers/hwmon/sbtsi_temp.c
> +++ b/drivers/hwmon/sbtsi_temp.c
> @@ -74,53 +74,52 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
> u32 attr, int channel, long *val)
> {
> struct sbtsi_data *data = dev_get_drvdata(dev);
> + u8 temp_int_reg, temp_dec_reg;
> s32 temp_int, temp_dec;
> int err;
>
> switch (attr) {
> case hwmon_temp_input:
> - /*
> - * ReadOrder bit specifies the reading order of integer and
> - * decimal part of CPU temp for atomic reads. If bit == 0,
> - * reading integer part triggers latching of the decimal part,
> - * so integer part should be read first. If bit == 1, read
> - * order should be reversed.
> - */
> - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> - if (err < 0)
> - return err;
> -
> - mutex_lock(&data->lock);
> - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> - } else {
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> - }
> - mutex_unlock(&data->lock);
> + temp_int_reg = SBTSI_REG_TEMP_INT;
> + temp_dec_reg = SBTSI_REG_TEMP_DEC;
> break;
> case hwmon_temp_max:
> - mutex_lock(&data->lock);
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
> - mutex_unlock(&data->lock);
> + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
> + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
> break;
> case hwmon_temp_min:
> - mutex_lock(&data->lock);
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
> - mutex_unlock(&data->lock);
> + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
> + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
> break;
> default:
> return -EINVAL;
> }
>
> + /*
> + * ReadOrder bit specifies the reading order of integer and
> + * decimal part of CPU temp for atomic reads. If bit == 0,
> + * reading integer part triggers latching of the decimal part,
> + * so integer part should be read first. If bit == 1, read
> + * order should be reversed.
> + */
> + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> + if (err < 0)
> + return err;
> +
It seems the "fix" is to always execute above code, which presumably
fails if the CPU is off. The downside of this approach is that it forces
an unnecessary extra and unnecessary i2c operation when reading
the limits.
The real fix would be to check for error after each i2c operation,
not only after both operations are complete.
> + mutex_lock(&data->lock);
> + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> + } else {
> + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> + }
> + mutex_unlock(&data->lock);
>
> - if (temp_int < 0)
> - return temp_int;
> if (temp_dec < 0)
> return temp_dec;
> + if (temp_int < 0)
> + return temp_int;
I don't see a value in swapping the checks.
Guenter
>
> *val = sbtsi_reg_to_mc(temp_int, temp_dec);
>
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-05 21:41 ` Guenter Roeck
@ 2021-04-06 18:16 ` Konstantin Aladyshev
2021-04-06 18:42 ` Guenter Roeck
0 siblings, 1 reply; 9+ messages in thread
From: Konstantin Aladyshev @ 2021-04-06 18:16 UTC (permalink / raw)
Cc: kunyi, Konstantin Aladyshev, Jean Delvare, Guenter Roeck,
linux-hwmon, linux-kernel
SBTSI sensors don't work when the CPU is off.
In this case every 'i2c_smbus_read_byte_data' function would fail
by a timeout.
Currently temp1_max/temp1_min file reads can cause two such timeouts
for every read.
Restructure code so there will be no more than one timeout for every
read operation.
Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
---
Changes in v2:
- Fix typo in a commit message
- Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
1 file changed, 27 insertions(+), 28 deletions(-)
diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
index e35357c48b8e..4ae48635bb31 100644
--- a/drivers/hwmon/sbtsi_temp.c
+++ b/drivers/hwmon/sbtsi_temp.c
@@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long *val)
{
struct sbtsi_data *data = dev_get_drvdata(dev);
+ u8 temp_int_reg, temp_dec_reg;
s32 temp_int, temp_dec;
int err;
switch (attr) {
case hwmon_temp_input:
- /*
- * ReadOrder bit specifies the reading order of integer and
- * decimal part of CPU temp for atomic reads. If bit == 0,
- * reading integer part triggers latching of the decimal part,
- * so integer part should be read first. If bit == 1, read
- * order should be reversed.
- */
- err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
- if (err < 0)
- return err;
-
- mutex_lock(&data->lock);
- if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
- } else {
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
- }
- mutex_unlock(&data->lock);
+ temp_int_reg = SBTSI_REG_TEMP_INT;
+ temp_dec_reg = SBTSI_REG_TEMP_DEC;
break;
case hwmon_temp_max:
- mutex_lock(&data->lock);
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
- mutex_unlock(&data->lock);
+ temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
+ temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
break;
case hwmon_temp_min:
- mutex_lock(&data->lock);
- temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
- temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
- mutex_unlock(&data->lock);
+ temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
+ temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
break;
default:
return -EINVAL;
}
+ /*
+ * ReadOrder bit specifies the reading order of integer and
+ * decimal part of CPU temp for atomic reads. If bit == 0,
+ * reading integer part triggers latching of the decimal part,
+ * so integer part should be read first. If bit == 1, read
+ * order should be reversed.
+ */
+ err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
+ if (err < 0)
+ return err;
+
+ mutex_lock(&data->lock);
+ if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
+ temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
+ temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
+ } else {
+ temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
+ temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
+ }
+ mutex_unlock(&data->lock);
if (temp_int < 0)
return temp_int;
--
2.25.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-06 18:16 ` [PATCH v2] " Konstantin Aladyshev
@ 2021-04-06 18:42 ` Guenter Roeck
[not found] ` <CACSj6VUCgxCQeA9EF4Oz+pKY+TdF9Gp=DV1V=-TcVE4ixtg45Q@mail.gmail.com>
0 siblings, 1 reply; 9+ messages in thread
From: Guenter Roeck @ 2021-04-06 18:42 UTC (permalink / raw)
To: Konstantin Aladyshev; +Cc: kunyi, Jean Delvare, linux-hwmon, linux-kernel
On 4/6/21 11:16 AM, Konstantin Aladyshev wrote:
> SBTSI sensors don't work when the CPU is off.
> In this case every 'i2c_smbus_read_byte_data' function would fail
> by a timeout.
> Currently temp1_max/temp1_min file reads can cause two such timeouts
> for every read.
> Restructure code so there will be no more than one timeout for every
> read operation.
>
> Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
> ---
> Changes in v2:
> - Fix typo in a commit message
> - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
>
This doesn't explain the reason for the extra read operation for
limits. Preventing a second read in error cases is not an argument
for adding an extra read for non-error cases.
Guenter
> drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
> 1 file changed, 27 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
> index e35357c48b8e..4ae48635bb31 100644
> --- a/drivers/hwmon/sbtsi_temp.c
> +++ b/drivers/hwmon/sbtsi_temp.c
> @@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
> u32 attr, int channel, long *val)
> {
> struct sbtsi_data *data = dev_get_drvdata(dev);
> + u8 temp_int_reg, temp_dec_reg;
> s32 temp_int, temp_dec;
> int err;
>
> switch (attr) {
> case hwmon_temp_input:
> - /*
> - * ReadOrder bit specifies the reading order of integer and
> - * decimal part of CPU temp for atomic reads. If bit == 0,
> - * reading integer part triggers latching of the decimal part,
> - * so integer part should be read first. If bit == 1, read
> - * order should be reversed.
> - */
> - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> - if (err < 0)
> - return err;
> -
> - mutex_lock(&data->lock);
> - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> - } else {
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> - }
> - mutex_unlock(&data->lock);
> + temp_int_reg = SBTSI_REG_TEMP_INT;
> + temp_dec_reg = SBTSI_REG_TEMP_DEC;
> break;
> case hwmon_temp_max:
> - mutex_lock(&data->lock);
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
> - mutex_unlock(&data->lock);
> + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
> + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
> break;
> case hwmon_temp_min:
> - mutex_lock(&data->lock);
> - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
> - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
> - mutex_unlock(&data->lock);
> + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
> + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
> break;
> default:
> return -EINVAL;
> }
>
> + /*
> + * ReadOrder bit specifies the reading order of integer and
> + * decimal part of CPU temp for atomic reads. If bit == 0,
> + * reading integer part triggers latching of the decimal part,
> + * so integer part should be read first. If bit == 1, read
> + * order should be reversed.
> + */
> + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> + if (err < 0)
> + return err;
> +
> + mutex_lock(&data->lock);
> + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> + } else {
> + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> + }
> + mutex_unlock(&data->lock);
>
> if (temp_int < 0)
> return temp_int;
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
[not found] ` <CACSj6VUCgxCQeA9EF4Oz+pKY+TdF9Gp=DV1V=-TcVE4ixtg45Q@mail.gmail.com>
@ 2021-04-06 20:09 ` Guenter Roeck
2021-04-06 21:09 ` Konstantin Aladyshev
0 siblings, 1 reply; 9+ messages in thread
From: Guenter Roeck @ 2021-04-06 20:09 UTC (permalink / raw)
To: Konstantin Aladyshev; +Cc: Kun Yi, Jean Delvare, linux-hwmon, linux-kernel
On 4/6/21 12:20 PM, Konstantin Aladyshev wrote:
> Thanks for the comment.
> Yes, you are correct, this patch adds an extra 'i2c_smbus_read_byte_data' call for the temp_max/temp_min reads.
> I guess I did that intentionally because I just wanted to keep the restructured code concise. After all I thought, 'temp_input' generally is read more often than 'temp_max/temp_min'.
> As I understand now, it seems like it is not acceptable. Therefore could you point me in the right direction about what I should do?
> Should I just stick with the original driver version and simply add two more i2c call checks for the first operations for min/max?
>
Correct, it is not acceptable. A normal use case for hwmon devices is to use the "sensors"
command which _will_ read all attributes. i2c reads are expensive, and unnecessary read
operations should be avoided.
There are several ways to solve the problem. Checking return values after each
read is the simple option. There are other possibilities, such as reading the limits
and the read order only once during probe, but I don't know enough about the
hardware to suggest a more sophisticated solution. For example, I don't know
what "CPU is off" means. Offline ? Not present ? If it means "not present",
or if the status is permanent, the condition should be handled in the is_visible
function (or the driver should not be instantiated in the first place).
Otherwise, the code should possibly return -ENODATA instead of -ETIMEDOUT
on error. But, again, I can not really suggest a better solution since
I don't know enough (nothing, actually) about the hardware (and the public
part of the SBTSI specification doesn't say anything about expected behavior
for offline CPUs or CPU cores).
What I did find, though, is that the driver does not implement temperature
offset support, and it that doesn't support reporting alerts. I'd have assumed
this to be more important than optimizing error handling, but that is just
my personal opinion.
Thanks,
Guenter
> Best regards,
> Konstantin Aladyshev
>
>
> On Tue, Apr 6, 2021 at 9:42 PM Guenter Roeck <linux@roeck-us.net <mailto:linux@roeck-us.net>> wrote:
>
> On 4/6/21 11:16 AM, Konstantin Aladyshev wrote:
> > SBTSI sensors don't work when the CPU is off.
> > In this case every 'i2c_smbus_read_byte_data' function would fail
> > by a timeout.
> > Currently temp1_max/temp1_min file reads can cause two such timeouts
> > for every read.
> > Restructure code so there will be no more than one timeout for every
> > read operation.
> >
> > Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com <mailto:aladyshev22@gmail.com>>
> > ---
> > Changes in v2:
> > - Fix typo in a commit message
> > - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
> >
>
> This doesn't explain the reason for the extra read operation for
> limits. Preventing a second read in error cases is not an argument
> for adding an extra read for non-error cases.
>
> Guenter
>
> > drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
> > 1 file changed, 27 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
> > index e35357c48b8e..4ae48635bb31 100644
> > --- a/drivers/hwmon/sbtsi_temp.c
> > +++ b/drivers/hwmon/sbtsi_temp.c
> > @@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
> > u32 attr, int channel, long *val)
> > {
> > struct sbtsi_data *data = dev_get_drvdata(dev);
> > + u8 temp_int_reg, temp_dec_reg;
> > s32 temp_int, temp_dec;
> > int err;
> >
> > switch (attr) {
> > case hwmon_temp_input:
> > - /*
> > - * ReadOrder bit specifies the reading order of integer and
> > - * decimal part of CPU temp for atomic reads. If bit == 0,
> > - * reading integer part triggers latching of the decimal part,
> > - * so integer part should be read first. If bit == 1, read
> > - * order should be reversed.
> > - */
> > - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> > - if (err < 0)
> > - return err;
> > -
> > - mutex_lock(&data->lock);
> > - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> > - } else {
> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> > - }
> > - mutex_unlock(&data->lock);
> > + temp_int_reg = SBTSI_REG_TEMP_INT;
> > + temp_dec_reg = SBTSI_REG_TEMP_DEC;
> > break;
> > case hwmon_temp_max:
> > - mutex_lock(&data->lock);
> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
> > - mutex_unlock(&data->lock);
> > + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
> > + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
> > break;
> > case hwmon_temp_min:
> > - mutex_lock(&data->lock);
> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
> > - mutex_unlock(&data->lock);
> > + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
> > + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
> > break;
> > default:
> > return -EINVAL;
> > }
> >
> > + /*
> > + * ReadOrder bit specifies the reading order of integer and
> > + * decimal part of CPU temp for atomic reads. If bit == 0,
> > + * reading integer part triggers latching of the decimal part,
> > + * so integer part should be read first. If bit == 1, read
> > + * order should be reversed.
> > + */
> > + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> > + if (err < 0)
> > + return err;
> > +
> > + mutex_lock(&data->lock);
> > + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> > + } else {
> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> > + }
> > + mutex_unlock(&data->lock);
> >
> > if (temp_int < 0)
> > return temp_int;
> >
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-06 20:09 ` Guenter Roeck
@ 2021-04-06 21:09 ` Konstantin Aladyshev
2021-04-06 21:34 ` Guenter Roeck
0 siblings, 1 reply; 9+ messages in thread
From: Konstantin Aladyshev @ 2021-04-06 21:09 UTC (permalink / raw)
To: Guenter Roeck; +Cc: Kun Yi, Jean Delvare, linux-hwmon, linux-kernel
Thanks for the answer!
Sorry for the confusion, by the "CPU is off" I meant "CPU is present,
but currently it is in the powered off state".
Therefore it is not possible to put these checks only in a probe
function. And I don't know either if it is a good idea to cache
config/min/max values.
I use this driver on an OpenBMC system, which uses other software
rather than lm-sensors utility. I guess that is why my priorities are
shifted.
By the way, I've noticed that the mutex check is absent in a
SBTSI_REG_CONFIG read call both in the original driver version and in
my patch, is this an error?
Best regards,
Konstantin Aladyshev
On Tue, Apr 6, 2021 at 11:09 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 4/6/21 12:20 PM, Konstantin Aladyshev wrote:
> > Thanks for the comment.
> > Yes, you are correct, this patch adds an extra 'i2c_smbus_read_byte_data' call for the temp_max/temp_min reads.
> > I guess I did that intentionally because I just wanted to keep the restructured code concise. After all I thought, 'temp_input' generally is read more often than 'temp_max/temp_min'.
> > As I understand now, it seems like it is not acceptable. Therefore could you point me in the right direction about what I should do?
> > Should I just stick with the original driver version and simply add two more i2c call checks for the first operations for min/max?
> >
>
> Correct, it is not acceptable. A normal use case for hwmon devices is to use the "sensors"
> command which _will_ read all attributes. i2c reads are expensive, and unnecessary read
> operations should be avoided.
>
> There are several ways to solve the problem. Checking return values after each
> read is the simple option. There are other possibilities, such as reading the limits
> and the read order only once during probe, but I don't know enough about the
> hardware to suggest a more sophisticated solution. For example, I don't know
> what "CPU is off" means. Offline ? Not present ? If it means "not present",
> or if the status is permanent, the condition should be handled in the is_visible
> function (or the driver should not be instantiated in the first place).
> Otherwise, the code should possibly return -ENODATA instead of -ETIMEDOUT
> on error. But, again, I can not really suggest a better solution since
> I don't know enough (nothing, actually) about the hardware (and the public
> part of the SBTSI specification doesn't say anything about expected behavior
> for offline CPUs or CPU cores).
>
> What I did find, though, is that the driver does not implement temperature
> offset support, and it that doesn't support reporting alerts. I'd have assumed
> this to be more important than optimizing error handling, but that is just
> my personal opinion.
>
> Thanks,
> Guenter
>
> > Best regards,
> > Konstantin Aladyshev
> >
> >
> > On Tue, Apr 6, 2021 at 9:42 PM Guenter Roeck <linux@roeck-us.net <mailto:linux@roeck-us.net>> wrote:
> >
> > On 4/6/21 11:16 AM, Konstantin Aladyshev wrote:
> > > SBTSI sensors don't work when the CPU is off.
> > > In this case every 'i2c_smbus_read_byte_data' function would fail
> > > by a timeout.
> > > Currently temp1_max/temp1_min file reads can cause two such timeouts
> > > for every read.
> > > Restructure code so there will be no more than one timeout for every
> > > read operation.
> > >
> > > Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com <mailto:aladyshev22@gmail.com>>
> > > ---
> > > Changes in v2:
> > > - Fix typo in a commit message
> > > - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
> > >
> >
> > This doesn't explain the reason for the extra read operation for
> > limits. Preventing a second read in error cases is not an argument
> > for adding an extra read for non-error cases.
> >
> > Guenter
> >
> > > drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
> > > 1 file changed, 27 insertions(+), 28 deletions(-)
> > >
> > > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
> > > index e35357c48b8e..4ae48635bb31 100644
> > > --- a/drivers/hwmon/sbtsi_temp.c
> > > +++ b/drivers/hwmon/sbtsi_temp.c
> > > @@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
> > > u32 attr, int channel, long *val)
> > > {
> > > struct sbtsi_data *data = dev_get_drvdata(dev);
> > > + u8 temp_int_reg, temp_dec_reg;
> > > s32 temp_int, temp_dec;
> > > int err;
> > >
> > > switch (attr) {
> > > case hwmon_temp_input:
> > > - /*
> > > - * ReadOrder bit specifies the reading order of integer and
> > > - * decimal part of CPU temp for atomic reads. If bit == 0,
> > > - * reading integer part triggers latching of the decimal part,
> > > - * so integer part should be read first. If bit == 1, read
> > > - * order should be reversed.
> > > - */
> > > - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> > > - if (err < 0)
> > > - return err;
> > > -
> > > - mutex_lock(&data->lock);
> > > - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> > > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> > > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> > > - } else {
> > > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> > > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> > > - }
> > > - mutex_unlock(&data->lock);
> > > + temp_int_reg = SBTSI_REG_TEMP_INT;
> > > + temp_dec_reg = SBTSI_REG_TEMP_DEC;
> > > break;
> > > case hwmon_temp_max:
> > > - mutex_lock(&data->lock);
> > > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
> > > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
> > > - mutex_unlock(&data->lock);
> > > + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
> > > + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
> > > break;
> > > case hwmon_temp_min:
> > > - mutex_lock(&data->lock);
> > > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
> > > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
> > > - mutex_unlock(&data->lock);
> > > + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
> > > + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
> > > break;
> > > default:
> > > return -EINVAL;
> > > }
> > >
> > > + /*
> > > + * ReadOrder bit specifies the reading order of integer and
> > > + * decimal part of CPU temp for atomic reads. If bit == 0,
> > > + * reading integer part triggers latching of the decimal part,
> > > + * so integer part should be read first. If bit == 1, read
> > > + * order should be reversed.
> > > + */
> > > + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> > > + if (err < 0)
> > > + return err;
> > > +
> > > + mutex_lock(&data->lock);
> > > + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> > > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> > > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> > > + } else {
> > > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> > > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> > > + }
> > > + mutex_unlock(&data->lock);
> > >
> > > if (temp_int < 0)
> > > return temp_int;
> > >
> >
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-06 21:09 ` Konstantin Aladyshev
@ 2021-04-06 21:34 ` Guenter Roeck
2021-04-06 22:25 ` Konstantin Aladyshev
0 siblings, 1 reply; 9+ messages in thread
From: Guenter Roeck @ 2021-04-06 21:34 UTC (permalink / raw)
To: Konstantin Aladyshev; +Cc: Kun Yi, Jean Delvare, linux-hwmon, linux-kernel
On 4/6/21 2:09 PM, Konstantin Aladyshev wrote:
> Thanks for the answer!
> Sorry for the confusion, by the "CPU is off" I meant "CPU is present,
> but currently it is in the powered off state".
> Therefore it is not possible to put these checks only in a probe
> function. And I don't know either if it is a good idea to cache
> config/min/max values.
>
> I use this driver on an OpenBMC system, which uses other software
> rather than lm-sensors utility. I guess that is why my priorities are
> shifted.
>
> By the way, I've noticed that the mutex check is absent in a
> SBTSI_REG_CONFIG read call both in the original driver version and in
> my patch, is this an error?
>
What do you mean with "mutex check" ?
Thanks,
Guenter
> Best regards,
> Konstantin Aladyshev
>
>
> On Tue, Apr 6, 2021 at 11:09 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On 4/6/21 12:20 PM, Konstantin Aladyshev wrote:
>>> Thanks for the comment.
>>> Yes, you are correct, this patch adds an extra 'i2c_smbus_read_byte_data' call for the temp_max/temp_min reads.
>>> I guess I did that intentionally because I just wanted to keep the restructured code concise. After all I thought, 'temp_input' generally is read more often than 'temp_max/temp_min'.
>>> As I understand now, it seems like it is not acceptable. Therefore could you point me in the right direction about what I should do?
>>> Should I just stick with the original driver version and simply add two more i2c call checks for the first operations for min/max?
>>>
>>
>> Correct, it is not acceptable. A normal use case for hwmon devices is to use the "sensors"
>> command which _will_ read all attributes. i2c reads are expensive, and unnecessary read
>> operations should be avoided.
>>
>> There are several ways to solve the problem. Checking return values after each
>> read is the simple option. There are other possibilities, such as reading the limits
>> and the read order only once during probe, but I don't know enough about the
>> hardware to suggest a more sophisticated solution. For example, I don't know
>> what "CPU is off" means. Offline ? Not present ? If it means "not present",
>> or if the status is permanent, the condition should be handled in the is_visible
>> function (or the driver should not be instantiated in the first place).
>> Otherwise, the code should possibly return -ENODATA instead of -ETIMEDOUT
>> on error. But, again, I can not really suggest a better solution since
>> I don't know enough (nothing, actually) about the hardware (and the public
>> part of the SBTSI specification doesn't say anything about expected behavior
>> for offline CPUs or CPU cores).
>>
>> What I did find, though, is that the driver does not implement temperature
>> offset support, and it that doesn't support reporting alerts. I'd have assumed
>> this to be more important than optimizing error handling, but that is just
>> my personal opinion.
>>
>> Thanks,
>> Guenter
>>
>>> Best regards,
>>> Konstantin Aladyshev
>>>
>>>
>>> On Tue, Apr 6, 2021 at 9:42 PM Guenter Roeck <linux@roeck-us.net <mailto:linux@roeck-us.net>> wrote:
>>>
>>> On 4/6/21 11:16 AM, Konstantin Aladyshev wrote:
>>> > SBTSI sensors don't work when the CPU is off.
>>> > In this case every 'i2c_smbus_read_byte_data' function would fail
>>> > by a timeout.
>>> > Currently temp1_max/temp1_min file reads can cause two such timeouts
>>> > for every read.
>>> > Restructure code so there will be no more than one timeout for every
>>> > read operation.
>>> >
>>> > Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com <mailto:aladyshev22@gmail.com>>
>>> > ---
>>> > Changes in v2:
>>> > - Fix typo in a commit message
>>> > - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
>>> >
>>>
>>> This doesn't explain the reason for the extra read operation for
>>> limits. Preventing a second read in error cases is not an argument
>>> for adding an extra read for non-error cases.
>>>
>>> Guenter
>>>
>>> > drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
>>> > 1 file changed, 27 insertions(+), 28 deletions(-)
>>> >
>>> > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
>>> > index e35357c48b8e..4ae48635bb31 100644
>>> > --- a/drivers/hwmon/sbtsi_temp.c
>>> > +++ b/drivers/hwmon/sbtsi_temp.c
>>> > @@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
>>> > u32 attr, int channel, long *val)
>>> > {
>>> > struct sbtsi_data *data = dev_get_drvdata(dev);
>>> > + u8 temp_int_reg, temp_dec_reg;
>>> > s32 temp_int, temp_dec;
>>> > int err;
>>> >
>>> > switch (attr) {
>>> > case hwmon_temp_input:
>>> > - /*
>>> > - * ReadOrder bit specifies the reading order of integer and
>>> > - * decimal part of CPU temp for atomic reads. If bit == 0,
>>> > - * reading integer part triggers latching of the decimal part,
>>> > - * so integer part should be read first. If bit == 1, read
>>> > - * order should be reversed.
>>> > - */
>>> > - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
>>> > - if (err < 0)
>>> > - return err;
>>> > -
>>> > - mutex_lock(&data->lock);
>>> > - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
>>> > - } else {
>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
>>> > - }
>>> > - mutex_unlock(&data->lock);
>>> > + temp_int_reg = SBTSI_REG_TEMP_INT;
>>> > + temp_dec_reg = SBTSI_REG_TEMP_DEC;
>>> > break;
>>> > case hwmon_temp_max:
>>> > - mutex_lock(&data->lock);
>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
>>> > - mutex_unlock(&data->lock);
>>> > + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
>>> > + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
>>> > break;
>>> > case hwmon_temp_min:
>>> > - mutex_lock(&data->lock);
>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
>>> > - mutex_unlock(&data->lock);
>>> > + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
>>> > + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
>>> > break;
>>> > default:
>>> > return -EINVAL;
>>> > }
>>> >
>>> > + /*
>>> > + * ReadOrder bit specifies the reading order of integer and
>>> > + * decimal part of CPU temp for atomic reads. If bit == 0,
>>> > + * reading integer part triggers latching of the decimal part,
>>> > + * so integer part should be read first. If bit == 1, read
>>> > + * order should be reversed.
>>> > + */
>>> > + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
>>> > + if (err < 0)
>>> > + return err;
>>> > +
>>> > + mutex_lock(&data->lock);
>>> > + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
>>> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
>>> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
>>> > + } else {
>>> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
>>> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
>>> > + }
>>> > + mutex_unlock(&data->lock);
>>> >
>>> > if (temp_int < 0)
>>> > return temp_int;
>>> >
>>>
>>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-06 21:34 ` Guenter Roeck
@ 2021-04-06 22:25 ` Konstantin Aladyshev
2021-04-06 23:28 ` Guenter Roeck
0 siblings, 1 reply; 9+ messages in thread
From: Konstantin Aladyshev @ 2021-04-06 22:25 UTC (permalink / raw)
To: Guenter Roeck; +Cc: Kun Yi, Jean Delvare, linux-hwmon, linux-kernel
What I'm trying to say, shouldn't the call
"i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG)" be
surrounded with the "mutex_lock/mutex_unlock" like it is done for the
others "i2c_smbus_read_byte_data" calls?
Something like:
```
mutex_lock(&data->lock);
err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
if (err < 0)
return err;
mutex_unlock(&data->lock);
```
Because it is not surrounded with the mutex lock/unlock in the original driver.
Best regards,
Konstantin Aladyshev
On Wed, Apr 7, 2021 at 12:34 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 4/6/21 2:09 PM, Konstantin Aladyshev wrote:
> > Thanks for the answer!
> > Sorry for the confusion, by the "CPU is off" I meant "CPU is present,
> > but currently it is in the powered off state".
> > Therefore it is not possible to put these checks only in a probe
> > function. And I don't know either if it is a good idea to cache
> > config/min/max values.
> >
> > I use this driver on an OpenBMC system, which uses other software
> > rather than lm-sensors utility. I guess that is why my priorities are
> > shifted.
> >
> > By the way, I've noticed that the mutex check is absent in a
> > SBTSI_REG_CONFIG read call both in the original driver version and in
> > my patch, is this an error?
> >
>
> What do you mean with "mutex check" ?
>
> Thanks,
> Guenter
>
>
> > Best regards,
> > Konstantin Aladyshev
> >
> >
> > On Tue, Apr 6, 2021 at 11:09 PM Guenter Roeck <linux@roeck-us.net> wrote:
> >>
> >> On 4/6/21 12:20 PM, Konstantin Aladyshev wrote:
> >>> Thanks for the comment.
> >>> Yes, you are correct, this patch adds an extra 'i2c_smbus_read_byte_data' call for the temp_max/temp_min reads.
> >>> I guess I did that intentionally because I just wanted to keep the restructured code concise. After all I thought, 'temp_input' generally is read more often than 'temp_max/temp_min'.
> >>> As I understand now, it seems like it is not acceptable. Therefore could you point me in the right direction about what I should do?
> >>> Should I just stick with the original driver version and simply add two more i2c call checks for the first operations for min/max?
> >>>
> >>
> >> Correct, it is not acceptable. A normal use case for hwmon devices is to use the "sensors"
> >> command which _will_ read all attributes. i2c reads are expensive, and unnecessary read
> >> operations should be avoided.
> >>
> >> There are several ways to solve the problem. Checking return values after each
> >> read is the simple option. There are other possibilities, such as reading the limits
> >> and the read order only once during probe, but I don't know enough about the
> >> hardware to suggest a more sophisticated solution. For example, I don't know
> >> what "CPU is off" means. Offline ? Not present ? If it means "not present",
> >> or if the status is permanent, the condition should be handled in the is_visible
> >> function (or the driver should not be instantiated in the first place).
> >> Otherwise, the code should possibly return -ENODATA instead of -ETIMEDOUT
> >> on error. But, again, I can not really suggest a better solution since
> >> I don't know enough (nothing, actually) about the hardware (and the public
> >> part of the SBTSI specification doesn't say anything about expected behavior
> >> for offline CPUs or CPU cores).
> >>
> >> What I did find, though, is that the driver does not implement temperature
> >> offset support, and it that doesn't support reporting alerts. I'd have assumed
> >> this to be more important than optimizing error handling, but that is just
> >> my personal opinion.
> >>
> >> Thanks,
> >> Guenter
> >>
> >>> Best regards,
> >>> Konstantin Aladyshev
> >>>
> >>>
> >>> On Tue, Apr 6, 2021 at 9:42 PM Guenter Roeck <linux@roeck-us.net <mailto:linux@roeck-us.net>> wrote:
> >>>
> >>> On 4/6/21 11:16 AM, Konstantin Aladyshev wrote:
> >>> > SBTSI sensors don't work when the CPU is off.
> >>> > In this case every 'i2c_smbus_read_byte_data' function would fail
> >>> > by a timeout.
> >>> > Currently temp1_max/temp1_min file reads can cause two such timeouts
> >>> > for every read.
> >>> > Restructure code so there will be no more than one timeout for every
> >>> > read operation.
> >>> >
> >>> > Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com <mailto:aladyshev22@gmail.com>>
> >>> > ---
> >>> > Changes in v2:
> >>> > - Fix typo in a commit message
> >>> > - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
> >>> >
> >>>
> >>> This doesn't explain the reason for the extra read operation for
> >>> limits. Preventing a second read in error cases is not an argument
> >>> for adding an extra read for non-error cases.
> >>>
> >>> Guenter
> >>>
> >>> > drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
> >>> > 1 file changed, 27 insertions(+), 28 deletions(-)
> >>> >
> >>> > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
> >>> > index e35357c48b8e..4ae48635bb31 100644
> >>> > --- a/drivers/hwmon/sbtsi_temp.c
> >>> > +++ b/drivers/hwmon/sbtsi_temp.c
> >>> > @@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
> >>> > u32 attr, int channel, long *val)
> >>> > {
> >>> > struct sbtsi_data *data = dev_get_drvdata(dev);
> >>> > + u8 temp_int_reg, temp_dec_reg;
> >>> > s32 temp_int, temp_dec;
> >>> > int err;
> >>> >
> >>> > switch (attr) {
> >>> > case hwmon_temp_input:
> >>> > - /*
> >>> > - * ReadOrder bit specifies the reading order of integer and
> >>> > - * decimal part of CPU temp for atomic reads. If bit == 0,
> >>> > - * reading integer part triggers latching of the decimal part,
> >>> > - * so integer part should be read first. If bit == 1, read
> >>> > - * order should be reversed.
> >>> > - */
> >>> > - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> >>> > - if (err < 0)
> >>> > - return err;
> >>> > -
> >>> > - mutex_lock(&data->lock);
> >>> > - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> >>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> >>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> >>> > - } else {
> >>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
> >>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
> >>> > - }
> >>> > - mutex_unlock(&data->lock);
> >>> > + temp_int_reg = SBTSI_REG_TEMP_INT;
> >>> > + temp_dec_reg = SBTSI_REG_TEMP_DEC;
> >>> > break;
> >>> > case hwmon_temp_max:
> >>> > - mutex_lock(&data->lock);
> >>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
> >>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
> >>> > - mutex_unlock(&data->lock);
> >>> > + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
> >>> > + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
> >>> > break;
> >>> > case hwmon_temp_min:
> >>> > - mutex_lock(&data->lock);
> >>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
> >>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
> >>> > - mutex_unlock(&data->lock);
> >>> > + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
> >>> > + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
> >>> > break;
> >>> > default:
> >>> > return -EINVAL;
> >>> > }
> >>> >
> >>> > + /*
> >>> > + * ReadOrder bit specifies the reading order of integer and
> >>> > + * decimal part of CPU temp for atomic reads. If bit == 0,
> >>> > + * reading integer part triggers latching of the decimal part,
> >>> > + * so integer part should be read first. If bit == 1, read
> >>> > + * order should be reversed.
> >>> > + */
> >>> > + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> >>> > + if (err < 0)
> >>> > + return err;
> >>> > +
> >>> > + mutex_lock(&data->lock);
> >>> > + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
> >>> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> >>> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> >>> > + } else {
> >>> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
> >>> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
> >>> > + }
> >>> > + mutex_unlock(&data->lock);
> >>> >
> >>> > if (temp_int < 0)
> >>> > return temp_int;
> >>> >
> >>>
> >>
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH v2] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond
2021-04-06 22:25 ` Konstantin Aladyshev
@ 2021-04-06 23:28 ` Guenter Roeck
0 siblings, 0 replies; 9+ messages in thread
From: Guenter Roeck @ 2021-04-06 23:28 UTC (permalink / raw)
To: Konstantin Aladyshev; +Cc: Kun Yi, Jean Delvare, linux-hwmon, linux-kernel
On 4/6/21 3:25 PM, Konstantin Aladyshev wrote:
> What I'm trying to say, shouldn't the call
> "i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG)" be
> surrounded with the "mutex_lock/mutex_unlock" like it is done for the
> others "i2c_smbus_read_byte_data" calls?
> Something like:
> ```
> mutex_lock(&data->lock);
> err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
> if (err < 0)
> return err;
> mutex_unlock(&data->lock);
> ```
> Because it is not surrounded with the mutex lock/unlock in the original driver.
>
Why would that be necessary ? My understanding is that the returned value
is read-only and won't change. FWIW, I don't even understand why it is
read more than once to start with.
On a side note, the above code would leave the mutex locked on error.
Guenter
> Best regards,
> Konstantin Aladyshev
>
>
> On Wed, Apr 7, 2021 at 12:34 AM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On 4/6/21 2:09 PM, Konstantin Aladyshev wrote:
>>> Thanks for the answer!
>>> Sorry for the confusion, by the "CPU is off" I meant "CPU is present,
>>> but currently it is in the powered off state".
>>> Therefore it is not possible to put these checks only in a probe
>>> function. And I don't know either if it is a good idea to cache
>>> config/min/max values.
>>>
>>> I use this driver on an OpenBMC system, which uses other software
>>> rather than lm-sensors utility. I guess that is why my priorities are
>>> shifted.
>>>
>>> By the way, I've noticed that the mutex check is absent in a
>>> SBTSI_REG_CONFIG read call both in the original driver version and in
>>> my patch, is this an error?
>>>
>>
>> What do you mean with "mutex check" ?
>>
>> Thanks,
>> Guenter
>>
>>
>>> Best regards,
>>> Konstantin Aladyshev
>>>
>>>
>>> On Tue, Apr 6, 2021 at 11:09 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>>>
>>>> On 4/6/21 12:20 PM, Konstantin Aladyshev wrote:
>>>>> Thanks for the comment.
>>>>> Yes, you are correct, this patch adds an extra 'i2c_smbus_read_byte_data' call for the temp_max/temp_min reads.
>>>>> I guess I did that intentionally because I just wanted to keep the restructured code concise. After all I thought, 'temp_input' generally is read more often than 'temp_max/temp_min'.
>>>>> As I understand now, it seems like it is not acceptable. Therefore could you point me in the right direction about what I should do?
>>>>> Should I just stick with the original driver version and simply add two more i2c call checks for the first operations for min/max?
>>>>>
>>>>
>>>> Correct, it is not acceptable. A normal use case for hwmon devices is to use the "sensors"
>>>> command which _will_ read all attributes. i2c reads are expensive, and unnecessary read
>>>> operations should be avoided.
>>>>
>>>> There are several ways to solve the problem. Checking return values after each
>>>> read is the simple option. There are other possibilities, such as reading the limits
>>>> and the read order only once during probe, but I don't know enough about the
>>>> hardware to suggest a more sophisticated solution. For example, I don't know
>>>> what "CPU is off" means. Offline ? Not present ? If it means "not present",
>>>> or if the status is permanent, the condition should be handled in the is_visible
>>>> function (or the driver should not be instantiated in the first place).
>>>> Otherwise, the code should possibly return -ENODATA instead of -ETIMEDOUT
>>>> on error. But, again, I can not really suggest a better solution since
>>>> I don't know enough (nothing, actually) about the hardware (and the public
>>>> part of the SBTSI specification doesn't say anything about expected behavior
>>>> for offline CPUs or CPU cores).
>>>>
>>>> What I did find, though, is that the driver does not implement temperature
>>>> offset support, and it that doesn't support reporting alerts. I'd have assumed
>>>> this to be more important than optimizing error handling, but that is just
>>>> my personal opinion.
>>>>
>>>> Thanks,
>>>> Guenter
>>>>
>>>>> Best regards,
>>>>> Konstantin Aladyshev
>>>>>
>>>>>
>>>>> On Tue, Apr 6, 2021 at 9:42 PM Guenter Roeck <linux@roeck-us.net <mailto:linux@roeck-us.net>> wrote:
>>>>>
>>>>> On 4/6/21 11:16 AM, Konstantin Aladyshev wrote:
>>>>> > SBTSI sensors don't work when the CPU is off.
>>>>> > In this case every 'i2c_smbus_read_byte_data' function would fail
>>>>> > by a timeout.
>>>>> > Currently temp1_max/temp1_min file reads can cause two such timeouts
>>>>> > for every read.
>>>>> > Restructure code so there will be no more than one timeout for every
>>>>> > read operation.
>>>>> >
>>>>> > Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com <mailto:aladyshev22@gmail.com>>
>>>>> > ---
>>>>> > Changes in v2:
>>>>> > - Fix typo in a commit message
>>>>> > - Don't swap temp_int/temp_dec checks at the end of the 'sbtsi_read' function
>>>>> >
>>>>>
>>>>> This doesn't explain the reason for the extra read operation for
>>>>> limits. Preventing a second read in error cases is not an argument
>>>>> for adding an extra read for non-error cases.
>>>>>
>>>>> Guenter
>>>>>
>>>>> > drivers/hwmon/sbtsi_temp.c | 55 +++++++++++++++++++-------------------
>>>>> > 1 file changed, 27 insertions(+), 28 deletions(-)
>>>>> >
>>>>> > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c
>>>>> > index e35357c48b8e..4ae48635bb31 100644
>>>>> > --- a/drivers/hwmon/sbtsi_temp.c
>>>>> > +++ b/drivers/hwmon/sbtsi_temp.c
>>>>> > @@ -74,48 +74,47 @@ static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
>>>>> > u32 attr, int channel, long *val)
>>>>> > {
>>>>> > struct sbtsi_data *data = dev_get_drvdata(dev);
>>>>> > + u8 temp_int_reg, temp_dec_reg;
>>>>> > s32 temp_int, temp_dec;
>>>>> > int err;
>>>>> >
>>>>> > switch (attr) {
>>>>> > case hwmon_temp_input:
>>>>> > - /*
>>>>> > - * ReadOrder bit specifies the reading order of integer and
>>>>> > - * decimal part of CPU temp for atomic reads. If bit == 0,
>>>>> > - * reading integer part triggers latching of the decimal part,
>>>>> > - * so integer part should be read first. If bit == 1, read
>>>>> > - * order should be reversed.
>>>>> > - */
>>>>> > - err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
>>>>> > - if (err < 0)
>>>>> > - return err;
>>>>> > -
>>>>> > - mutex_lock(&data->lock);
>>>>> > - if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
>>>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
>>>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
>>>>> > - } else {
>>>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
>>>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
>>>>> > - }
>>>>> > - mutex_unlock(&data->lock);
>>>>> > + temp_int_reg = SBTSI_REG_TEMP_INT;
>>>>> > + temp_dec_reg = SBTSI_REG_TEMP_DEC;
>>>>> > break;
>>>>> > case hwmon_temp_max:
>>>>> > - mutex_lock(&data->lock);
>>>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
>>>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
>>>>> > - mutex_unlock(&data->lock);
>>>>> > + temp_int_reg = SBTSI_REG_TEMP_HIGH_INT;
>>>>> > + temp_dec_reg = SBTSI_REG_TEMP_HIGH_DEC;
>>>>> > break;
>>>>> > case hwmon_temp_min:
>>>>> > - mutex_lock(&data->lock);
>>>>> > - temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
>>>>> > - temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
>>>>> > - mutex_unlock(&data->lock);
>>>>> > + temp_int_reg = SBTSI_REG_TEMP_LOW_INT;
>>>>> > + temp_dec_reg = SBTSI_REG_TEMP_LOW_DEC;
>>>>> > break;
>>>>> > default:
>>>>> > return -EINVAL;
>>>>> > }
>>>>> >
>>>>> > + /*
>>>>> > + * ReadOrder bit specifies the reading order of integer and
>>>>> > + * decimal part of CPU temp for atomic reads. If bit == 0,
>>>>> > + * reading integer part triggers latching of the decimal part,
>>>>> > + * so integer part should be read first. If bit == 1, read
>>>>> > + * order should be reversed.
>>>>> > + */
>>>>> > + err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
>>>>> > + if (err < 0)
>>>>> > + return err;
>>>>> > +
>>>>> > + mutex_lock(&data->lock);
>>>>> > + if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
>>>>> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
>>>>> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
>>>>> > + } else {
>>>>> > + temp_int = i2c_smbus_read_byte_data(data->client, temp_int_reg);
>>>>> > + temp_dec = i2c_smbus_read_byte_data(data->client, temp_dec_reg);
>>>>> > + }
>>>>> > + mutex_unlock(&data->lock);
>>>>> >
>>>>> > if (temp_int < 0)
>>>>> > return temp_int;
>>>>> >
>>>>>
>>>>
>>
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2021-04-06 23:28 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-04-01 21:45 [PATCH] hwmon: (sbtsi) Don't read sensor more than once if it doesn't respond Konstantin Aladyshev
2021-04-05 21:41 ` Guenter Roeck
2021-04-06 18:16 ` [PATCH v2] " Konstantin Aladyshev
2021-04-06 18:42 ` Guenter Roeck
[not found] ` <CACSj6VUCgxCQeA9EF4Oz+pKY+TdF9Gp=DV1V=-TcVE4ixtg45Q@mail.gmail.com>
2021-04-06 20:09 ` Guenter Roeck
2021-04-06 21:09 ` Konstantin Aladyshev
2021-04-06 21:34 ` Guenter Roeck
2021-04-06 22:25 ` Konstantin Aladyshev
2021-04-06 23:28 ` Guenter Roeck
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