[PATCH v2] gpio/omap: fix off-mode bug: clear debounce clock enable mask on free/reset
From: Jon Hunter <hidden>
Date: 2012-10-25 13:11:13
Also in:
linux-omap
On 10/25/2012 02:00 AM, Santosh Shilimkar wrote:
On Thursday 25 October 2012 04:24 AM, Jon Hunter wrote:quoted
On 10/24/2012 12:10 PM, Kevin Hilman wrote:quoted
From: Kevin Hilman <redacted> When a GPIO bank is freed or shutdown, ensure that the banks dbck_enable_mask is cleared also. Otherwise, context restore on subsequent off-mode transition will restore previous value from the shadow copies (bank->context.debounce*) leading to mismatch state between driver state and hardware state. This was discovered when board code was doing gpio_request_one() gpio_set_debounce() gpio_free() which was leaving the GPIO debounce settings in a confused state. If that GPIO bank is subsequently used with off-mode enabled, bogus state would be restored, leaving GPIO debounce enabled which then prevented the CORE powerdomain from transitioning. To fix, ensure that bank->dbck_enable_mask is cleared when the bank is freed/shutdown so debounce state doesn't persist.The freed part is fine but I don't understand why it needs to be done on _a_ gpio irq shutdown callback where IRQs related configuration on that one GPIO needs to be cleared. De-bounce clock is surely not IRQ related configuration.
If we are freeing the IRQs related to gpio and resetting the gpio, then I don't see why we should not. We should not leave the debounce clock on if these gpios are no longer being used.
quoted hunk ↗ jump to hunk
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Special thanks to Grazvydas Ignotas for pointing out a bug in an earlier version that would've disabled debounce on any runtime PM transition. Reported-by: Paul Walmsley <paul@pwsan.com> Cc: Igor Grinberg <redacted> Cc: Grazvydas Ignotas <redacted> Signed-off-by: Kevin Hilman <redacted> --- v2: only clear mask in free/shutdown, not in runtime PM paths, clarified changelog Applies on v3.7-rc2. drivers/gpio/gpio-omap.c | 1 + 1 file changed, 1 insertion(+)diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c index 94cbc84..113b167 100644 --- a/drivers/gpio/gpio-omap.c +++ b/drivers/gpio/gpio-omap.c@@ -539,6 +539,7 @@ static void _reset_gpio(struct gpio_bank *bank,int gpio) _set_gpio_irqenable(bank, gpio, 0); _clear_gpio_irqstatus(bank, gpio); _set_gpio_triggering(bank, GPIO_INDEX(bank, gpio), IRQ_TYPE_NONE); + bank->dbck_enable_mask = 0; }Does this need to be ... + bank->dbck_enable_mask &= ~(GPIO_BIT(bank, gpio)); + _gpio_dbck_disable(bank);Yes, its a per bank clock. There is an alternate. See below.quoted
There could be more than one gpio using debounce and so we should only clear the appropriate bit. Also after clearing a bit we could see if we can disable the debounce clock too.When I mentioned the clearing in gpio_free() path will do trick, I had something like below in mind.diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c index dee2856..8574105 100644 --- a/drivers/gpio/gpio-omap.c +++ b/drivers/gpio/gpio-omap.c@@ -629,8 +629,10 @@ static void omap_gpio_free(struct gpio_chip *chip,unsigned offset) * If this is the last gpio to be freed in the bank, * disable the bank module. */ - if (!bank->mod_usage) + if (!bank->mod_usage) { + bank->dbck_enable_mask = 0; pm_runtime_put(bank->dev); + }
However, with this we could be leaving the debounce clock on longer than needed. I think we need to call _gpio_dbck_disable() each time we free a gpio and this function will determine if it can turn off the debounce clock. In fact, there appears to be another bug in the current driver, that we do not clear the debounce_en register when freeing the gpio. Your patch addresses this, but I think that debounce should be disabled when a gpio is freed and not just when the last one is freed. Also, with the above change, can't we still run into the original problem? In other words, if a gpio is freed, but there is still another one active in the back that is not using debounce, then we could restore a incorrect debounce context because we have not clean-up the debounce settings? So may be we need to add a _clear_gpio_debounce() function and call this when freeing a gpio. Cheers Jon