[PATCH 8/8] gpio/omap: fix missing check in *_runtime_suspend()

DebBarma, Tarun Kanti
2012-05-18T05:12:48Z

On Fri, May 18, 2012 at 3:51 AM, Kevin Hilman <khilman@ti.com> wrote:
> Tarun, Santosh,
>
> Tarun Kanti DebBarma <tarun.kanti@ti.com> writes:
>
>> We do checking for bank->enabled_non_wakeup_gpios in order
>> to skip redundant operations. Somehow, the check got missed
>> while doing the cleanup series.
>>
>> Just to make sure that we do context restore correctly in
>> *_runtime_resume(), the bank->workaround_enabled check is
>> moved after context restore. Otherwise, it would prevent
>> context restore when bank->enabled_non_wakeup_gpios is 0.
>>
>> Cc: Kevin Hilman <khilman@ti.com>
>> Cc: Tony Lindgren <tony@atomide.com>
>> Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
>> Cc: Cousson, Benoit <b-cousson@ti.com>
>> Cc: Grant Likely <grant.likely@secretlab.ca>
>> Signed-off-by: Tarun Kanti DebBarma <tarun.kanti@ti.com>
>
> I just noticed that this patch has caused some strange problems, notably
> with the GPIO IRQ used by smsc911x NIC (Overo, Zoom3, 2430SDP, etc. etc.)
>
> The patch itself is OK, but it has exposed a bug in other parts of the
> context restore path that was previously hidden.
>
> We seem to have been finding lots of GPIO bugs by just testing the
> network chips with GPIO IRQs. ?Can I suggest that a platform with a GPIO
> IRQ NIC be added to the test platforms you're using?
>
>> ---
>> ?drivers/gpio/gpio-omap.c | ? 13 ++++++++-----
>> ?1 files changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>> index d238f84..59a4af1 100644
>> --- a/drivers/gpio/gpio-omap.c
>> +++ b/drivers/gpio/gpio-omap.c
>> @@ -1160,6 +1160,9 @@ static int omap_gpio_runtime_suspend(struct device *dev)
>>
>> ? ? ? spin_lock_irqsave(&bank->lock, flags);
>>
>> + ? ? if (!bank->enabled_non_wakeup_gpios)
>> + ? ? ? ? ? ? goto update_gpio_context_count;
>> +
>> ? ? ? /*
>> ? ? ? ?* Only edges can generate a wakeup event to the PRCM.
>> ? ? ? ?*
>> @@ -1235,11 +1238,6 @@ static int omap_gpio_runtime_resume(struct device *dev)
>> ? ? ? __raw_writel(bank->context.risingdetect,
>> ? ? ? ? ? ? ? ? ? ?bank->base + bank->regs->risingdetect);
>>
>> - ? ? if (!bank->workaround_enabled) {
>> - ? ? ? ? ? ? spin_unlock_irqrestore(&bank->lock, flags);
>> - ? ? ? ? ? ? return 0;
>> - ? ? }
>> -
>
> My moving this below, you exposed some buggy code that can now get
> executed in non-OFF mode, wherease before $SUBJECT patch, it would never
> be exectued in non-OFF mode.
>
>> ? ? ? if (bank->get_context_loss_count) {
>> ? ? ? ? ? ? ? context_lost_cnt_after =
>> ? ? ? ? ? ? ? ? ? ? ? bank->get_context_loss_count(bank->dev);
>
> ...right below this line, we have:
>
> ? ? ? ? ? ? ? ?if (context_lost_cnt_after != bank->context_loss_count ||
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?!context_lost_cnt_after) {
> ? ? ? ? ? ? ? ? ? ? ? ?omap_gpio_restore_context(bank);
>
> While we've never hit off-mode, context_lost_cnt_after will always be
> zero. ?However, becasue of the !context_lost_cnt_after check there, we
> will *always* restore the bank context, even though context has never
> been lost.
>
> I have no idea why that !context_lost_cnt_after check is there, but
> clearly it is wrong. ?Now that you moved the 'workraound_enabled' check
> below this section, as long as off-mode is disabled, the some GPIO
> context will be restored here on *every* runtime PM transition.
>
> The patch below fixes the problem.
>
> Grant, after Tarun/Santosh have a chance to review/ack this, can you
> still get this in for 3.5? ?If not, getting it into -rc should be fine.
>
> Kevin
>
>
> From 83874df8e0dd78a3609f5ba81d608df7217fd212 Mon Sep 17 00:00:00 2001
> From: Kevin Hilman <khilman@ti.com>
> Date: Thu, 17 May 2012 14:52:56 -0700
> Subject: [PATCH] gpio/omap: fix broken context restore for non-OFF mode
> ?transitions
>
> The fix in commit 1b12870 (gpio/omap: fix missing check in
> *_runtime_suspend()) exposed another bug in the context restore path.
>
> Currently, the per-bank context restore happens whenever the context
> loss count is different in runtime suspend and runtime resume *and*
> whenever the per-bank contex_loss_count == 0:
>
> ? ? ? ?if (context_lost_cnt_after != bank->context_loss_count ||
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?!context_lost_cnt_after) {
> ? ? ? ? ? ? ? ?omap_gpio_restore_context(bank);
>
> Restoring context when the context_lost_cnt_after == 0 is clearly
> wrong, since this will be true until the first off-mode transition
> (which could be never, if off-mode is never enabled.) ?This check
> causes the context to be restored on *every* runtime PM transition.
>
> Before commit 1b12870 (gpio/omap: fix missing check in
> *_runtime_suspend()), this code was never executed in non-OFF mode, so
> there were never spurious context restores happening. ?After that
> change though, spurious context restores could happen.
>
> To fix, simply remove the !context_lost_cnt_after check. It is not
> needed.
>
> This bug was found when noticing that the smc911x NIC on 3530/Overo
> was not working, and git bisect tracked it down to this patch. ?It
> seems that the spurious context restore was causing the smsc911x to
> not be properly probed on this platform.
>
> Cc: Tarun Kanti DebBarma <tarun.kanti@ti.com>
> Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
> Signed-off-by: Kevin Hilman <khilman@ti.com>

Acked-by: Tarun Kanti DebBarma <tarun.kanti@ti.com>

> ---
> ?drivers/gpio/gpio-omap.c | ? ?3 +--
> ?1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index 9b71f04..b570a6a 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -1238,8 +1238,7 @@ static int omap_gpio_runtime_resume(struct device *dev)
> ? ? ? ?if (bank->get_context_loss_count) {
> ? ? ? ? ? ? ? ?context_lost_cnt_after =
> ? ? ? ? ? ? ? ? ? ? ? ?bank->get_context_loss_count(bank->dev);
> - ? ? ? ? ? ? ? if (context_lost_cnt_after != bank->context_loss_count ||
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? !context_lost_cnt_after) {
> + ? ? ? ? ? ? ? if (context_lost_cnt_after != bank->context_loss_count) {
> ? ? ? ? ? ? ? ? ? ? ? ?omap_gpio_restore_context(bank);
> ? ? ? ? ? ? ? ?} else {
> ? ? ? ? ? ? ? ? ? ? ? ?spin_unlock_irqrestore(&bank->lock, flags);
> --
> 1.7.9.2
>