Re: [PATCH 5/5] Input: ads7846: set proper debounce time in driver level

Igor Grinberg
2012-06-12T07:53:58Z

On 06/12/12 05:49, Zumeng Chen wrote:
>
>
> 2012/6/11 Igor Grinberg <grinberg@compulab.co.il <mailto:grinberg@compulab.co.il>>
>
> Hi,
>
> This is input subsystem, add Dmitry and linux-input.
>
> On 06/11/12 17:00, Zumeng Chen wrote:
> > If we don't set proper debouce time for ads7846, then there are
> > flooded interrupt counters of ads7846 responding to one time
> > touch on screen, so the driver couldn't work well.
> >
> > And since most OMAP3 series boards pass NULL pointer of board_pdata
> > to omap_ads7846_init, so it's more proper to set it in driver level
> > after having gpio_request done.
>
> What about other non-OMAP platforms?
>
> Good point, I thought it should be the same situation, and I have no other boards
> to validate it :) Then I'll fall back on my original patch to bracket them with OMAP3EVM

This isn't a good solution either...

>
>
> NULL pointer for board_pdata, only means that the default pdata is used.
> Please, see the common-board-devices.c file more closely.
>
> Yes, I just went through again, two points:
>
> 1 ) get_pendown_state is not set for OMAP3 boards, and the state

You can supply your own pdata and provide the get_pendown_state() callback.

> will be get by gpio_get_value(gpio-omap.c)
> The second path will be available in the ads7846_setup_pendown
> if (pdata->get_pendown_state) {
> ts->get_pendown_state = pdata->get_pendown_state;
> } else if (gpio_is_valid(pdata->gpio_pendown)) {
>
> 2 ) All omap3 boards set gpio_pendown for pdata.
> So it had better we set_debounce in driver level after gpio_request_one
> having done
> I'll remove DEBOUNCE_TIME in V2 and change into like following:
>
> +#ifdef CONFIG_MACH_OMAP3EVM
> + /* 310 means 10 microsecond for omap3 */
> + gpio_set_debounce(pdata->gpio_pendown, 310);
> +#endif

I don't think this kind of fix is acceptable...

>
>
> >
> > This patch has been validated on 3530evm.
> >
> > Signed-off-by: Zumeng Chen <zumeng.chen@gmail.com <mailto:zumeng.chen@gmail.com>>
> > Signed-off-by: Syed Mohammed Khasim <khasim@ti.com <mailto:khasim@ti.com>>
> > Signed-off-by: Tony Lindgren <tony@atomide.com <mailto:tony@atomide.com>>
> > ---
> > drivers/input/touchscreen/ads7846.c | 2 ++
> > 1 files changed, 2 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
> > index f02028e..a82a5fb 100644
> > --- a/drivers/input/touchscreen/ads7846.c
> > +++ b/drivers/input/touchscreen/ads7846.c
> > @@ -61,6 +61,7 @@
> >
> > /* this driver doesn't aim at the peak continuous sample rate */
> > #define SAMPLE_BITS (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
> > +#define DEBOUNCE_TIME 310 /* About 10 ms */
>
> I think hard coding this value is wrong.
>
> Yes, me too.
>
> Can't it be derived from the pdata->debounce_* fields?
>
> Yes, I agreed this way, and to be honest, my first choice
> is to find if there is a member for debounce, but no. And
> there is no more sense to derive it from debounce_max,
> although which is the right value for us.

It makes sense to me... Why do you think there is no sense?

--
Regards,
Igor.