[PATCH 0/2] mmc: improve power-on for sdio wifi card.

[PATCH 0/2] mmc: improve power-on for sdio wifi card.

[NeilBrown]

These two patches improve power-on management for my 'libertas'
wifi card.

On my board the card shares a regulator with a bluetooth device, so
turning off the regulator may not powercycle the card.  To get it to a
clean state it is necessary to hold the reset line down while enabling
the regulator.

So the first patch add a reset-gpio function for all sdio cards
which is configured through devicetree.

The sequence of commands sent to the sdio device for power-up differs
between runtime power resume (which works nicely) and system-suspend
resume (which doesn't).
The second patch add to calls to make these sequences the same and
allowed my device to work reliably after system suspend (though the
libertas driver needs a bit of work before it is completely reliable).

Thanks,
NeilBrown
---

NeilBrown (2):
      mmc: core: allow a reset gpio to be configured.
      mmc: core: reset sdio card properly on resume.


 Documentation/devicetree/bindings/mmc/mmc.txt |    3 +
 drivers/mmc/core/core.c                       |    3 +
 drivers/mmc/core/host.c                       |   12 ++++
 drivers/mmc/core/sdio.c                       |    8 ++-
 drivers/mmc/core/slot-gpio.c                  |   70 +++++++++++++++++++++++++
 include/linux/mmc/slot-gpio.h                 |    4 +
 6 files changed, 97 insertions(+), 3 deletions(-)

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[PATCH 1/2] mmc: core: allow a reset gpio to be configured.

[NeilBrown]

If the regulator supplying an SDIO device is shared
with another device, the turning the regulator 'on' and 'off'
will not actually cycle power and so will not reset
the device.

This is particularly a problem for some wi2si wireless modules which
have a BT module on chip and can share power lines.
Without the power-cycle, subsequent reset commands fail.

So allow a 'reset' gpio to be specified.  If provided, the
line is asserted during power-up.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 Documentation/devicetree/bindings/mmc/mmc.txt |    3 +
 drivers/mmc/core/core.c                       |    3 +
 drivers/mmc/core/host.c                       |   12 ++++
 drivers/mmc/core/slot-gpio.c                  |   70 +++++++++++++++++++++++++
 include/linux/mmc/slot-gpio.h                 |    4 +
 5 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
index 431716e37a39..06b84b3bb3ee 100644
--- a/Documentation/devicetree/bindings/mmc/mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/mmc.txt
@@ -21,6 +21,9 @@ Optional properties:
   below for the case, when a GPIO is used for the CD line
 - wp-inverted: when present, polarity on the WP line is inverted. See the note
   below for the case, when a GPIO is used for the WP line
+- reset-gpios: Specify a GPIO to be asserted during power-up. This is
+  useful is power is not actually removed (e.g. due to shared
+  regulator) but a reset is needed before reconfiguration.
 - max-frequency: maximum operating clock frequency
 - no-1-8-v: when present, denotes that 1.8v card voltage is not supported on
   this system, even if the controller claims it is.
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index d03a080fb9cd..64572c44f9b5 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1533,6 +1533,8 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
 
 	mmc_host_clk_hold(host);
 
+	/* Reset during power-off */
+	mmc_gpio_set_rs(host, 1);
 	host->ios.vdd = fls(ocr) - 1;
 	if (mmc_host_is_spi(host))
 		host->ios.chip_select = MMC_CS_HIGH;
@@ -1568,6 +1570,7 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
 	 * time required to reach a stable voltage.
 	 */
 	mmc_delay(10);
+	mmc_gpio_set_rs(host, 0);
 
 	mmc_host_clk_release(host);
 }
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 95cceae96944..42dbf7a521d4 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -415,6 +415,18 @@ int mmc_of_parse(struct mmc_host *host)
 	if (explicit_inv_wp ^ gpio_inv_wp)
 		host->caps2 |= MMC_CAP2_RO_ACTIVE_HIGH;
 
+	gpio = of_get_named_gpio_flags(np, "reset-gpios", 0, &flags);
+	if (gpio == -EPROBE_DEFER) {
+		ret = -EPROBE_DEFER;
+		goto out;
+	}
+	if (gpio_is_valid(gpio)) {
+		ret = mmc_gpio_request_rs(host, gpio,
+					  flags & OF_GPIO_ACTIVE_LOW);
+		if (ret < 0)
+			goto out;
+	}
+
 	if (of_find_property(np, "cap-sd-highspeed", &len))
 		host->caps |= MMC_CAP_SD_HIGHSPEED;
 	if (of_find_property(np, "cap-mmc-highspeed", &len))
diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c
index f3bc51f9aba9..354034a8519f 100644
--- a/drivers/mmc/core/slot-gpio.c
+++ b/drivers/mmc/core/slot-gpio.c
@@ -21,10 +21,12 @@
 struct mmc_gpio {
 	struct gpio_desc *ro_gpio;
 	struct gpio_desc *cd_gpio;
+	struct gpio_desc *rs_gpio; /* reset line */
 	bool override_ro_active_level;
 	bool override_cd_active_level;
 	irqreturn_t (*cd_gpio_isr)(int irq, void *dev_id);
 	char *ro_label;
+	char *rs_label;
 	char cd_label[0];
 };
 
@@ -53,12 +55,14 @@ static int mmc_gpio_alloc(struct mmc_host *host)
 		 * before device_add(), i.e., between mmc_alloc_host() and
 		 * mmc_add_host()
 		 */
-		ctx = devm_kzalloc(&host->class_dev, sizeof(*ctx) + 2 * len,
+		ctx = devm_kzalloc(&host->class_dev, sizeof(*ctx) + 3 * len,
 				   GFP_KERNEL);
 		if (ctx) {
 			ctx->ro_label = ctx->cd_label + len;
+			ctx->rs_label = ctx->ro_label + len;
 			snprintf(ctx->cd_label, len, "%s cd", dev_name(host->parent));
 			snprintf(ctx->ro_label, len, "%s ro", dev_name(host->parent));
+			snprintf(ctx->rs_label, len, "%s rs", dev_name(host->parent));
 			host->slot.handler_priv = ctx;
 		}
 	}
@@ -98,6 +102,18 @@ int mmc_gpio_get_cd(struct mmc_host *host)
 }
 EXPORT_SYMBOL(mmc_gpio_get_cd);
 
+void mmc_gpio_set_rs(struct mmc_host *host, int state)
+{
+	struct mmc_gpio *ctx = host->slot.handler_priv;
+
+	if (!ctx || !ctx->rs_gpio)
+		return;
+
+	gpiod_set_value_cansleep(ctx->rs_gpio, state);
+}
+EXPORT_SYMBOL(mmc_gpio_set_rs);
+
+
 /**
  * mmc_gpio_request_ro - request a gpio for write-protection
  * @host: mmc host
@@ -138,6 +154,36 @@ int mmc_gpio_request_ro(struct mmc_host *host, unsigned int gpio)
 }
 EXPORT_SYMBOL(mmc_gpio_request_ro);
 
+int mmc_gpio_request_rs(struct mmc_host *host, unsigned int gpio, int low)
+{
+	struct mmc_gpio *ctx;
+	int ret;
+	int flags;
+
+	if (!gpio_is_valid(gpio))
+		return -EINVAL;
+
+	ret = mmc_gpio_alloc(host);
+	if (ret < 0)
+		return ret;
+
+	ctx = host->slot.handler_priv;
+	if (low)
+		flags = GPIOF_DIR_OUT | GPIOF_INIT_HIGH | GPIOF_ACTIVE_LOW;
+	else
+		flags = GPIOF_DIR_OUT | GPIOF_INIT_LOW;
+
+	ret = devm_gpio_request_one(&host->class_dev, gpio,
+				    flags, ctx->rs_label);
+	if (ret < 0)
+		return ret;
+
+	ctx->rs_gpio = gpio_to_desc(gpio);
+
+	return 0;
+}
+EXPORT_SYMBOL(mmc_gpio_request_rs);
+
 void mmc_gpiod_request_cd_irq(struct mmc_host *host)
 {
 	struct mmc_gpio *ctx = host->slot.handler_priv;
@@ -269,6 +315,28 @@ void mmc_gpio_free_ro(struct mmc_host *host)
 EXPORT_SYMBOL(mmc_gpio_free_ro);
 
 /**
+ * mmc_gpio_free_rs - free the reset gpio
+ * @host: mmc host
+ *
+ * It's provided only for cases that client drivers need to manually free
+ * up the write-protection gpio requested by mmc_gpio_request_rs().
+ */
+void mmc_gpio_free_rs(struct mmc_host *host)
+{
+	struct mmc_gpio *ctx = host->slot.handler_priv;
+	int gpio;
+
+	if (!ctx || !ctx->rs_gpio)
+		return;
+
+	gpio = desc_to_gpio(ctx->rs_gpio);
+	ctx->rs_gpio = NULL;
+
+	devm_gpio_free(&host->class_dev, gpio);
+}
+EXPORT_SYMBOL(mmc_gpio_free_rs);
+
+/**
  * mmc_gpio_free_cd - free the card-detection gpio
  * @host: mmc host
  *
diff --git a/include/linux/mmc/slot-gpio.h b/include/linux/mmc/slot-gpio.h
index a119892cebdb..630e39af2035 100644
--- a/include/linux/mmc/slot-gpio.h
+++ b/include/linux/mmc/slot-gpio.h
@@ -22,6 +22,10 @@ int mmc_gpio_request_cd(struct mmc_host *host, unsigned int gpio,
 			unsigned int debounce);
 void mmc_gpio_free_cd(struct mmc_host *host);
 
+void mmc_gpio_set_rs(struct mmc_host *host, int state);
+int mmc_gpio_request_rs(struct mmc_host *host, unsigned int gpio, int inv);
+void mmc_gpio_free_rs(struct mmc_host *host);
+
 int mmc_gpiod_request_cd(struct mmc_host *host, const char *con_id,
 			 unsigned int idx, bool override_active_level,
 			 unsigned int debounce);

[PATCH 2/2] mmc: core: reset sdio card properly on resume.

[NeilBrown]

mmc_sdio_power_restore calls
	mmc_send_if_cond(host, host->ocr_avail);

	ret = mmc_send_io_op_cond(host, 0, NULL);

between mmc_go_idle() and  mmc_sdio_init_card().
mmc_sdio_resume needs to as well, else my libertas sdio wifi
device doesn't resume properly from suspend.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 drivers/mmc/core/sdio.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index e636d9e99e4a..3f069a6f448f 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -981,8 +981,12 @@ static int mmc_sdio_resume(struct mmc_host *host)
 	if (mmc_card_is_removable(host) || !mmc_card_keep_power(host)) {
 		sdio_reset(host);
 		mmc_go_idle(host);
-		err = mmc_sdio_init_card(host, host->card->ocr, host->card,
-					mmc_card_keep_power(host));
+		mmc_send_if_cond(host, host->ocr_avail);
+		err = mmc_send_io_op_cond(host, 0, NULL);
+		if (!err)
+			err = mmc_sdio_init_card(host, host->card->ocr,
+						 host->card,
+						 mmc_card_keep_power(host));
 	} else if (mmc_card_keep_power(host) && mmc_card_wake_sdio_irq(host)) {
 		/* We may have switched to 1-bit mode during suspend */
 		err = sdio_enable_4bit_bus(host->card);

Re: [PATCH 2/2] mmc: core: reset sdio card properly on resume.

[Ulf Hansson]

On 8 November 2014 01:14, NeilBrown <neilb@suse.de> wrote:
> mmc_sdio_power_restore calls
>         mmc_send_if_cond(host, host->ocr_avail);
>
>         ret = mmc_send_io_op_cond(host, 0, NULL);
>
> between mmc_go_idle() and  mmc_sdio_init_card().
> mmc_sdio_resume needs to as well, else my libertas sdio wifi
> device doesn't resume properly from suspend.
>
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  drivers/mmc/core/sdio.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index e636d9e99e4a..3f069a6f448f 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -981,8 +981,12 @@ static int mmc_sdio_resume(struct mmc_host *host)
>         if (mmc_card_is_removable(host) || !mmc_card_keep_power(host)) {
>                 sdio_reset(host);
>                 mmc_go_idle(host);
> -               err = mmc_sdio_init_card(host, host->card->ocr, host->card,
> -                                       mmc_card_keep_power(host));
> +               mmc_send_if_cond(host, host->ocr_avail);

/s /host->ocr_avail /host->card->ocr

I would expect that to work. I do realize that "host->ocr_avail" is
being used in the ->power_restore() callback, but I think that's wrong
as well. Could you maybe verify that changing to host->card->ocr works
in this path as well? That's would of course be a separate patch.

> +               err = mmc_send_io_op_cond(host, 0, NULL);
> +               if (!err)
> +                       err = mmc_sdio_init_card(host, host->card->ocr,
> +                                                host->card,
> +                                                mmc_card_keep_power(host));
>         } else if (mmc_card_keep_power(host) && mmc_card_wake_sdio_irq(host)) {
>                 /* We may have switched to 1-bit mode during suspend */
>                 err = sdio_enable_4bit_bus(host->card);
>
>

Kind regards
Uffe

Re: [PATCH 2/2] mmc: core: reset sdio card properly on resume.

[NeilBrown]

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On Mon, 10 Nov 2014 14:29:19 +0100 Ulf Hansson <ulf.hansson-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:

> On 8 November 2014 01:14, NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org> wrote:
> > mmc_sdio_power_restore calls
> >         mmc_send_if_cond(host, host->ocr_avail);
> >
> >         ret = mmc_send_io_op_cond(host, 0, NULL);
> >
> > between mmc_go_idle() and  mmc_sdio_init_card().
> > mmc_sdio_resume needs to as well, else my libertas sdio wifi
> > device doesn't resume properly from suspend.
> >
> > Signed-off-by: NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org>
> > ---
> >  drivers/mmc/core/sdio.c |    8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> > index e636d9e99e4a..3f069a6f448f 100644
> > --- a/drivers/mmc/core/sdio.c
> > +++ b/drivers/mmc/core/sdio.c
> > @@ -981,8 +981,12 @@ static int mmc_sdio_resume(struct mmc_host *host)
> >         if (mmc_card_is_removable(host) || !mmc_card_keep_power(host)) {
> >                 sdio_reset(host);
> >                 mmc_go_idle(host);
> > -               err = mmc_sdio_init_card(host, host->card->ocr, host->card,
> > -                                       mmc_card_keep_power(host));
> > +               mmc_send_if_cond(host, host->ocr_avail);
> 
> /s /host->ocr_avail /host->card->ocr
> 
> I would expect that to work. I do realize that "host->ocr_avail" is
> being used in the ->power_restore() callback, but I think that's wrong
> as well. Could you maybe verify that changing to host->card->ocr works
> in this path as well? That's would of course be a separate patch.

Hi Ulf,
 I made the substitution in mmc_sdio_resume and mmc_sdio_power_restore
and my sdio device continues to work, including after resume.

The  host->card->ocr value is 0x10000, the host->ocr_avail value is 0x18000.

If you like I'll send the two patches formally, but it might be a day or so.

Thanks,
NeilBrown


> 
> > +               err = mmc_send_io_op_cond(host, 0, NULL);
> > +               if (!err)
> > +                       err = mmc_sdio_init_card(host, host->card->ocr,
> > +                                                host->card,
> > +                                                mmc_card_keep_power(host));
> >         } else if (mmc_card_keep_power(host) && mmc_card_wake_sdio_irq(host)) {
> >                 /* We may have switched to 1-bit mode during suspend */
> >                 err = sdio_enable_4bit_bus(host->card);
> >
> >
> 
> Kind regards
> Uffe


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Re: [PATCH 2/2] mmc: core: reset sdio card properly on resume.

[Ulf Hansson]

On 11 November 2014 01:17, NeilBrown <neilb@suse.de> wrote:
> On Mon, 10 Nov 2014 14:29:19 +0100 Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
>> On 8 November 2014 01:14, NeilBrown <neilb@suse.de> wrote:
>> > mmc_sdio_power_restore calls
>> >         mmc_send_if_cond(host, host->ocr_avail);
>> >
>> >         ret = mmc_send_io_op_cond(host, 0, NULL);
>> >
>> > between mmc_go_idle() and  mmc_sdio_init_card().
>> > mmc_sdio_resume needs to as well, else my libertas sdio wifi
>> > device doesn't resume properly from suspend.
>> >
>> > Signed-off-by: NeilBrown <neilb@suse.de>
>> > ---
>> >  drivers/mmc/core/sdio.c |    8 ++++++--
>> >  1 file changed, 6 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
>> > index e636d9e99e4a..3f069a6f448f 100644
>> > --- a/drivers/mmc/core/sdio.c
>> > +++ b/drivers/mmc/core/sdio.c
>> > @@ -981,8 +981,12 @@ static int mmc_sdio_resume(struct mmc_host *host)
>> >         if (mmc_card_is_removable(host) || !mmc_card_keep_power(host)) {
>> >                 sdio_reset(host);
>> >                 mmc_go_idle(host);
>> > -               err = mmc_sdio_init_card(host, host->card->ocr, host->card,
>> > -                                       mmc_card_keep_power(host));
>> > +               mmc_send_if_cond(host, host->ocr_avail);
>>
>> /s /host->ocr_avail /host->card->ocr
>>
>> I would expect that to work. I do realize that "host->ocr_avail" is
>> being used in the ->power_restore() callback, but I think that's wrong
>> as well. Could you maybe verify that changing to host->card->ocr works
>> in this path as well? That's would of course be a separate patch.
>
> Hi Ulf,
>  I made the substitution in mmc_sdio_resume and mmc_sdio_power_restore
> and my sdio device continues to work, including after resume.
>
> The  host->card->ocr value is 0x10000, the host->ocr_avail value is 0x18000.

That makes sense.

The host->card->ocr mask has been negotiated at initialization between
the host and the card.

>
> If you like I'll send the two patches formally, but it might be a day or so.

Please do.

Kind regards
Uffe

Re: [PATCH 1/2] mmc: core: allow a reset gpio to be configured.

[Ulf Hansson]

On 8 November 2014 at 01:14, NeilBrown <neilb@suse.de> wrote:
> If the regulator supplying an SDIO device is shared
> with another device, the turning the regulator 'on' and 'off'
> will not actually cycle power and so will not reset
> the device.
>
> This is particularly a problem for some wi2si wireless modules which
> have a BT module on chip and can share power lines.
> Without the power-cycle, subsequent reset commands fail.
>
> So allow a 'reset' gpio to be specified.  If provided, the
> line is asserted during power-up.

There have been several attempts to fix similar issues as this patch
does. The latest one I posted a few month ago, which wasn't accepted.
http://comments.gmane.org/gmane.linux.power-management.general/46635

There has also been some off-list discussions on especially how we
should describe this in DT and there were actually some consensus made
around that. Still I haven't seen any patches on the mailing lists.

So to summarize, I am really concerned that we keep having these power
sequence issues for SDIO devices and right now the discussion has been
on hold. I am considering to hack on it myself, since I am tired of
waiting. :-)

Regarding this patch, I don't intent to apply it.

Kind regards
Uffe

Re: [PATCH 1/2] mmc: core: allow a reset gpio to be configured.

[Mark Brown]

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On Fri, Nov 28, 2014 at 12:56:33PM +0100, Ulf Hansson wrote:
> On 8 November 2014 at 01:14, NeilBrown <neilb@suse.de> wrote:

> > If the regulator supplying an SDIO device is shared
> > with another device, the turning the regulator 'on' and 'off'
> > will not actually cycle power and so will not reset
> > the device.

> > This is particularly a problem for some wi2si wireless modules which
> > have a BT module on chip and can share power lines.
> > Without the power-cycle, subsequent reset commands fail.

> > So allow a 'reset' gpio to be specified.  If provided, the
> > line is asserted during power-up.

> There have been several attempts to fix similar issues as this patch
> does. The latest one I posted a few month ago, which wasn't accepted.
> http://comments.gmane.org/gmane.linux.power-management.general/46635

Note also that if the issue is about needing to take different actions
depending on if the power actually got pulled you can request
notification from the regulator API when things actually happen.

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Re: [PATCH 1/2] mmc: core: allow a reset gpio to be configured.

[NeilBrown]

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On Fri, 28 Nov 2014 12:56:33 +0100 Ulf Hansson <ulf.hansson@linaro.org> wrote:

> On 8 November 2014 at 01:14, NeilBrown <neilb@suse.de> wrote:
> > If the regulator supplying an SDIO device is shared
> > with another device, the turning the regulator 'on' and 'off'
> > will not actually cycle power and so will not reset
> > the device.
> >
> > This is particularly a problem for some wi2si wireless modules which
> > have a BT module on chip and can share power lines.
> > Without the power-cycle, subsequent reset commands fail.
> >
> > So allow a 'reset' gpio to be specified.  If provided, the
> > line is asserted during power-up.
> 
> There have been several attempts to fix similar issues as this patch
> does. The latest one I posted a few month ago, which wasn't accepted.
> http://comments.gmane.org/gmane.linux.power-management.general/46635

Thanks for that link.

> 
> There has also been some off-list discussions on especially how we
> should describe this in DT and there were actually some consensus made
> around that. Still I haven't seen any patches on the mailing lists.

Wish I could have a link for those off-list discussions :-)

Based on what I read and my own thoughts about other devices that I'm having
trouble managing I wonder if the right approach might be to admit that these
buses are *not* 100% discoverable.

i.e. you can discover what is there once it is turned on, but you cannot
discover how to turn it on.

So the *fix* is to allow attached devices to be explicitly listed.
In my case I would create a child node of the mmc1 node, which is
compatible="libertas,wifi" (or whatever the proper name is).

Then when the mmc1 wants to power-up, it does:

   device_for_each_child(mmc_dev, NULL, power_up)

where:

static int power_up(struct device *dev, void *data)
{
       pm_runtime_get_sync(dev);
       return 0;
}

Then I can put my reset-line management in the libertas driver instead of
trying to include some of it in the mmc driver.

This has the advantage of the devicetree actually describing the hardware
(there is a libertas wifi SDIO chip attached) rather than the behaviour
(please turn on this regulator and toggle this GPIO to initialise the device).

I want to do a very similar thing for UARTs (so my GPS and Bluetooth turn on
when /dev/ttyO? is opened), and I've been thinking about something similar
for USB - I have a USB attached GSM module, but it also has an Audio link and
some reset/interrupt lines that need to be configured.
If I could say to device tree "This USB port has this device attached", I
think it would be a step in the right direction.



> 
> So to summarize, I am really concerned that we keep having these power
> sequence issues for SDIO devices and right now the discussion has been
> on hold. I am considering to hack on it myself, since I am tired of
> waiting. :-)

Please Cc me if you do.  Meanwhile I'll try to hack together code supporting
my latest idea and let you know if I get anywhere.

> 
> Regarding this patch, I don't intent to apply it.

Fair enough, I'm starting to not like it so much anyway.

Thanks,
NeilBrown



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Re: [Gta04-owner] [PATCH 1/2] mmc: core: allow a reset gpio to be configured.

[Dr. H. Nikolaus Schaller]

Hi Neil,

Am 02.12.2014 um 02:55 schrieb NeilBrown <neilb@suse.de>:

> On Fri, 28 Nov 2014 12:56:33 +0100 Ulf Hansson <ulf.hansson@linaro.org> wrote:
> 
>> On 8 November 2014 at 01:14, NeilBrown <neilb@suse.de> wrote:
>>> If the regulator supplying an SDIO device is shared
>>> with another device, the turning the regulator 'on' and 'off'
>>> will not actually cycle power and so will not reset
>>> the device.
>>> 
>>> This is particularly a problem for some wi2si wireless modules which
>>> have a BT module on chip and can share power lines.
>>> Without the power-cycle, subsequent reset commands fail.
>>> 
>>> So allow a 'reset' gpio to be specified.  If provided, the
>>> line is asserted during power-up.
>> 
>> There have been several attempts to fix similar issues as this patch
>> does. The latest one I posted a few month ago, which wasn't accepted.
>> http://comments.gmane.org/gmane.linux.power-management.general/46635
> 
> Thanks for that link.
> 
>> 
>> There has also been some off-list discussions on especially how we
>> should describe this in DT and there were actually some consensus made
>> around that. Still I haven't seen any patches on the mailing lists.
> 
> Wish I could have a link for those off-list discussions :-)
> 
> Based on what I read and my own thoughts about other devices that I'm having
> trouble managing I wonder if the right approach might be to admit that these
> buses are *not* 100% discoverable.
> 
> i.e. you can discover what is there once it is turned on, but you cannot
> discover how to turn it on.

Indeed.

> 
> So the *fix* is to allow attached devices to be explicitly listed.
> In my case I would create a child node of the mmc1 node, which is
> compatible=“libertas,wifi" (or whatever the proper name is).

Sounds like a good idea to me.

> 
> Then when the mmc1 wants to power-up, it does:
> 
>   device_for_each_child(mmc_dev, NULL, power_up)
> 
> where:
> 
> static int power_up(struct device *dev, void *data)
> {
>       pm_runtime_get_sync(dev);
>       return 0;
> }
> 
> Then I can put my reset-line management in the libertas driver instead of
> trying to include some of it in the mmc driver.
> 
> This has the advantage of the devicetree actually describing the hardware
> (there is a libertas wifi SDIO chip attached) rather than the behaviour
> (please turn on this regulator and toggle this GPIO to initialise the device).
> 
> I want to do a very similar thing for UARTs (so my GPS and Bluetooth turn on
> when /dev/ttyO? is opened), and I've been thinking about something similar
> for USB - I have a USB attached GSM module, but it also has an Audio link and
> some reset/interrupt lines that need to be configured.
> If I could say to device tree "This USB port has this device attached", I
> think it would be a step in the right direction.

Thinking a little further, it could either be the core driver of the device/bus/protocol
or a special driver that only does power management. Or audio.

And we should consider using a list of strings in the compatible entry so that
several drivers can be loaded if the subsystem structure shows that this is simpler.

It could be one for power, one for audio. Or in the case of the libertas a separate
power&reset driver for a specific chip that uses the libertas driver so that chip
specific reset management is not introduced into the libertas core but separate.

For the usb connected modem the subnode to be attached is likely the PHY
where the self-powered device is connected to.

> 
> 
> 
>> 
>> So to summarize, I am really concerned that we keep having these power
>> sequence issues for SDIO devices and right now the discussion has been
>> on hold. I am considering to hack on it myself, since I am tired of
>> waiting. :-)
> 
> Please Cc me if you do.  Meanwhile I'll try to hack together code supporting
> my latest idea and let you know if I get anywhere.
> 
>> 
>> Regarding this patch, I don't intent to apply it.
> 
> Fair enough, I’m starting to not like it so much anyway.
> 

BR,
Nikolaus

Re: [PATCH 1/2] mmc: core: allow a reset gpio to be configured.

[Ulf Hansson]

On 2 December 2014 at 02:55, NeilBrown <neilb@suse.de> wrote:
> On Fri, 28 Nov 2014 12:56:33 +0100 Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
>> On 8 November 2014 at 01:14, NeilBrown <neilb@suse.de> wrote:
>> > If the regulator supplying an SDIO device is shared
>> > with another device, the turning the regulator 'on' and 'off'
>> > will not actually cycle power and so will not reset
>> > the device.
>> >
>> > This is particularly a problem for some wi2si wireless modules which
>> > have a BT module on chip and can share power lines.
>> > Without the power-cycle, subsequent reset commands fail.
>> >
>> > So allow a 'reset' gpio to be specified.  If provided, the
>> > line is asserted during power-up.
>>
>> There have been several attempts to fix similar issues as this patch
>> does. The latest one I posted a few month ago, which wasn't accepted.
>> http://comments.gmane.org/gmane.linux.power-management.general/46635
>
> Thanks for that link.
>
>>
>> There has also been some off-list discussions on especially how we
>> should describe this in DT and there were actually some consensus made
>> around that. Still I haven't seen any patches on the mailing lists.
>
> Wish I could have a link for those off-list discussions :-)
>
> Based on what I read and my own thoughts about other devices that I'm having
> trouble managing I wonder if the right approach might be to admit that these
> buses are *not* 100% discoverable.
>
> i.e. you can discover what is there once it is turned on, but you cannot
> discover how to turn it on.
>
> So the *fix* is to allow attached devices to be explicitly listed.
> In my case I would create a child node of the mmc1 node, which is
> compatible="libertas,wifi" (or whatever the proper name is).
>
> Then when the mmc1 wants to power-up, it does:
>
>    device_for_each_child(mmc_dev, NULL, power_up)
>
> where:
>
> static int power_up(struct device *dev, void *data)
> {
>        pm_runtime_get_sync(dev);

No. We must not rely on runtime PM to be able to power up the device.

>        return 0;
> }
>
> Then I can put my reset-line management in the libertas driver instead of
> trying to include some of it in the mmc driver.

Well, "somewhere" we need to handle the different power up scenarios.
These scenarios should be considered as SOC specific, and if we could
keep that as a separate piece of code, that would be the best.

So, I agree that we shouldn't pollute mmc host drivers with such code,
but I also think SDIO func drivers should be remained untouched.

Instead, my plan is to let the mmc core handle it.

>
> This has the advantage of the devicetree actually describing the hardware
> (there is a libertas wifi SDIO chip attached) rather than the behaviour
> (please turn on this regulator and toggle this GPIO to initialise the device).

I think both ways are viable, since they are both describing the
hardware and the characteristics of it.

>
> I want to do a very similar thing for UARTs (so my GPS and Bluetooth turn on
> when /dev/ttyO? is opened), and I've been thinking about something similar
> for USB - I have a USB attached GSM module, but it also has an Audio link and
> some reset/interrupt lines that need to be configured.
> If I could say to device tree "This USB port has this device attached", I
> think it would be a step in the right direction.
>
>
>
>>
>> So to summarize, I am really concerned that we keep having these power
>> sequence issues for SDIO devices and right now the discussion has been
>> on hold. I am considering to hack on it myself, since I am tired of
>> waiting. :-)
>
> Please Cc me if you do.  Meanwhile I'll try to hack together code supporting
> my latest idea and let you know if I get anywhere.

Sounds good. I have started hacking on it as well, let's see where we end up.

Kind regards
Uffe