Hi,
On Wed, Mar 04, 2009 at 11:59:13AM -0800, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> From: Eric Miao <eric.miao@xxxxxxxxxxx>
>
> Noises can be introduced when LCD signals are being driven, some platforms
> provide a signal to assist the synchronization of this sampling procedure.
>
> Signed-off-by: Eric Miao <eric.miao@xxxxxxxxxxx>
> Cc: David Brownell <david-b@xxxxxxxxxxx>
> Cc: Dmitry Torokhov <dtor@xxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> drivers/input/touchscreen/ads7846.c | 10 ++++++++++
> include/linux/spi/ads7846.h | 2 ++
> 2 files changed, 12 insertions(+)
>
> diff -puN drivers/input/touchscreen/ads7846.c~input-ads7846-introduce-platform-specific-way-to-synchronize-sampling drivers/input/touchscreen/ads7846.c
> --- a/drivers/input/touchscreen/ads7846.c~input-ads7846-introduce-platform-specific-way-to-synchronize-sampling
> +++ a/drivers/input/touchscreen/ads7846.c
> @@ -127,6 +127,8 @@ struct ads7846 {
> void (*filter_cleanup)(void *data);
> int (*get_pendown_state)(void);
> int gpio_pendown;
> +
> + void (*wait_for_sync)(void);
> };
>
> /* leave chip selected when we're done, for quicker re-select? */
> @@ -511,6 +513,10 @@ static int get_pendown_state(struct ads7
> return !gpio_get_value(ts->gpio_pendown);
> }
>
> +static void null_wait_for_sync(void)
> +{
> +}
> +
> /*
> * PENIRQ only kicks the timer. The timer only reissues the SPI transfer,
> * to retrieve touchscreen status.
> @@ -686,6 +692,7 @@ static void ads7846_rx_val(void *ads)
> default:
> BUG();
> }
> + ts->wait_for_sync();
> status = spi_async(ts->spi, m);
> if (status)
> dev_err(&ts->spi->dev, "spi_async --> %d\n",
> @@ -723,6 +730,7 @@ static enum hrtimer_restart ads7846_time
> } else {
> /* pen is still down, continue with the measurement */
> ts->msg_idx = 0;
> + ts->wait_for_sync();
We are in hard IRQ context here. What is the expectation of
wait_for_sync()? How long are we waiting here?
--
Dmitry
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