On Fri, Oct 26, 2012 at 9:26 PM, Jon Hunter <jon-hunter@xxxxxx> wrote: > This change was originally titled "gpio/omap: fix off-mode bug: clear debounce > clock enable mask on free/reset". The title has been updated slightly to > reflect (what should be) the final fix. > > When a GPIO is freed or shutdown, we need to ensure that any debounce settings > are cleared and if the GPIO is the only GPIO in the bank that is currently > using debounce, then disable the debounce clock as well to save power. > > Currently, the debounce settings are not cleared on a GPIO free or shutdown and > so during a context restore on subsequent off-mode transition, the previous > debounce values are restored 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 this, introduce a new function called _clear_gpio_debounce() to clear > any debounce settings when the GPIO is freed or shutdown. If this GPIO is the > last debounce-enabled GPIO in the bank, the debounce will also be cut. > > Please note that we cannot use _gpio_dbck_disable() to disable the debounce > clock because this has been specifically created for the gpio suspend path > and is intended to shutdown the debounce clock while debounce is enabled. > > Special thanks to Kevin Hilman for root causing the bug. This fix is a > collaborative effort with inputs from Kevin Hilman, Grazvydas Ignotas and > Santosh Shilimkar. > > Testing: > - This has been unit tested on an OMAP3430 Beagle board, by requesting a gpio, > enabling debounce and then freeing the gpio and checking the register > contents, the saved register context and the debounce clock state. > - Kevin Hilman tested on 37xx/EVM board which configures GPIO debounce for the > ads7846 touchscreen in its board file using the above sequence, and so was > failing off-mode tests in dynamic idle. Verified that off-mode tests are > passing with this patch. > > V5 changes: > - Corrected author > > Reported-by: Paul Walmsley <paul@xxxxxxxxx> > Cc: Igor Grinberg <grinberg@xxxxxxxxxxxxxx> > Cc: Grazvydas Ignotas <notasas@xxxxxxxxx> > Cc: Jon Hunter <jon-hunter@xxxxxx> > Signed-off-by: Jon Hunter <jon-hunter@xxxxxx> > Reviewed-by: Kevin Hilman <khilman@xxxxxx> > Tested-by: Kevin Hilman <khilman@xxxxxx> > Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> Hey there is a version I requested, with ACKs and all. You must be reading my mind :-D OK patch applied for fixes. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
