Hi, On Mon, Jul 29, 2013 at 07:45:10PM +0300, Illia Smyrnov wrote: > From: Axel Haslam <axelhaslam@xxxxxx> > > Set debounce time value to 12ms to workaround the errata. > > ERRATA DESCRIPTION: > When a key is released for a time shorter than the debounce time, > in-between 2 key press (KP1 and KP2), the keyboard state machine will go to > idle mode and will never detect the key release (after KP1,and also after KP2), > and thus will never generate a new IRQ indicating the key release. > From the operating system standpoint, only a key press as been detected, > and the key will keep on being printed on the screen until another or > the same key is pressed again.When the failing state has been reached, > the KBD_STATEMACHINE register will show "idle state" and the KBD_FULLCODE > register won't be empty, this is the signature of the bug.There is no impact > on the power consumption of the system as the state machine goes to IDLE state. > > WORKAROUND: > First thing is to program the debounce time correctly: > If X (us) is the maximum time of bounces when a key is pressed or released, > and Y (us) is the minimum time of a key release that is expected to be detected, > then the debounce time should be set to a value inbetween X and Y. > > In case it is still possible to get shorter than debounce time key-release > events, then the only solution is to implement a software workaround: > > Before printing a second character on the screen, the software must check if > the keyboard has hit the failing condition (cf signature of the bug above) > or if the key is still really pressed and then take the appropriate actions. > > Silicon revisions impacted: OMAP4430 ES 1.0,2.0,2.1,2.2,2.3 > OMAP4460 ES 1.0,1.1 > OMAP5430 ES 1.0 if only these are affected, should you have revision check ? Also we don't support OMAP5430 ES 1.0. I say this because, IMO, debouncing time is likely to be board-specific and/or application-specific. > diff --git a/drivers/input/keyboard/omap4-keypad.c b/drivers/input/keyboard/omap4-keypad.c > index feab00f..e8bdc76 100644 > --- a/drivers/input/keyboard/omap4-keypad.c > +++ b/drivers/input/keyboard/omap4-keypad.c > @@ -62,8 +62,10 @@ > > /* OMAP4 values */ > #define OMAP4_VAL_IRQDISABLE 0x0 > -#define OMAP4_VAL_DEBOUNCINGTIME 0x7 > -#define OMAP4_VAL_PVT 0x7 > + > +/* Errata i689: set debounce time value to 12ms */ > +#define OMAP4_VAL_DEBOUNCINGTIME 0x2 > +#define OMAP4_VAL_PVT 0x6 to make this easier to understand, you might want to convert this into a better macro that takes an argument in microseconds and you calculate the debouncing time which should be written to HW. -- balbi
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