On Tue, Oct 06, 2015 at 05:00:10PM +0300, Igor Grinberg wrote:
> From: Andrey Gelman <[email protected]>
>
> According to the touch controller spec, SPI return a 16 bit value,
> only 12 bits are valid, they are bit[14-3].
>
> The value of MISO and MOSI can be configured when SPI is in idle mode.
> Currently this touch driver assumes the SPI bus sets the MOSI and
> MISO in low level when SPI bus is in idle mode. So the bit[15] of the
> value got from SPI bus is always 0. But when SPI bus congfigures the
> MOSI and MISO in high level during the SPI idle mode, the bit[15] of
> the value get from SPI is always 1. If bit[15] is not masked, we may
> get the wrong value.
>
> Mask the invalid bit to make sure the correct value gets returned.
> Regardless of the SPI bus idle configuration.
>
> Signed-off-by: Andrey Gelman <[email protected]>
> Signed-off-by: Haibo Chen <[email protected]>
> Signed-off-by: Igor Grinberg <[email protected]>
Applied, thank you.
> ---
> drivers/input/touchscreen/ads7846.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/input/touchscreen/ads7846.c
> b/drivers/input/touchscreen/ads7846.c
> index 727d88c..8e2a44d 100644
> --- a/drivers/input/touchscreen/ads7846.c
> +++ b/drivers/input/touchscreen/ads7846.c
> @@ -666,18 +666,22 @@ static int ads7846_no_filter(void *ads, int data_idx,
> int *val)
>
> static int ads7846_get_value(struct ads7846 *ts, struct spi_message *m)
> {
> + int value;
> struct spi_transfer *t =
> list_entry(m->transfers.prev, struct spi_transfer,
> transfer_list);
>
> if (ts->model == 7845) {
> - return be16_to_cpup((__be16 *)&(((char*)t->rx_buf)[1])) >> 3;
> + value = be16_to_cpup((__be16 *)&(((char*)t->rx_buf)[1]));
> } else {
> /*
> * adjust: on-wire is a must-ignore bit, a BE12 value, then
> * padding; built from two 8 bit values written msb-first.
> */
> - return be16_to_cpup((__be16 *)t->rx_buf) >> 3;
> + value = be16_to_cpup((__be16 *)t->rx_buf);
> }
> +
> + /* enforce ADC output is 12 bits width */
> + return (value >> 3) & 0xfff;
> }
>
> static void ads7846_update_value(struct spi_message *m, int val)
> --
> 2.4.9
>
--
Dmitry
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