2023-01-20 13:20:05

by Luca Ellero

Subject: [PATCH 2/3] Input: ads7846 - always set last command to PWRDOWN

Controllers that report pressure (e.g. ADS7846) use 5 commands and the
correct sequence is READ_X, READ_Y, READ_Z1, READ_Z2, PWRDOWN.

Controllers that don't report pressure (e.g. ADS7845/ADS7843) use only 3
commands and the correct sequence should be READ_X, READ_Y, PWRDOWN. But
the sequence sent was incorrect: READ_X, READ_Y, READ_Z1.

Fix this by setting the third (and last) command to PWRDOWN.

Signed-off-by: Luca Ellero <[email protected]>
---
drivers/input/touchscreen/ads7846.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index f11b444f2138..15da1047a577 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -1066,6 +1066,9 @@ static int ads7846_setup_spi_msg(struct ads7846 *ts,
struct ads7846_buf_layout *l = &packet->l[cmd_idx];
unsigned int max_count;

+ if (cmd_idx == packet->cmds - 1)
+ cmd_idx = ADS7846_PWDOWN;
+
if (ads7846_cmd_need_settle(cmd_idx))
max_count = packet->count + packet->count_skip;
else
@@ -1102,7 +1105,12 @@ static int ads7846_setup_spi_msg(struct ads7846 *ts,

for (cmd_idx = 0; cmd_idx < packet->cmds; cmd_idx++) {
struct ads7846_buf_layout *l = &packet->l[cmd_idx];
- u8 cmd = ads7846_get_cmd(cmd_idx, vref);
+ u8 cmd;
+
+ if (cmd_idx == packet->cmds - 1)
+ cmd_idx = ADS7846_PWDOWN;
+
+ cmd = ads7846_get_cmd(cmd_idx, vref);

for (b = 0; b < l->count; b++)
packet->tx[l->offset + b].cmd = cmd;
--
2.25.1

2023-01-20 15:38:03

by Andy Shevchenko

Subject: Re: [PATCH 2/3] Input: ads7846 - always set last command to PWRDOWN

On Fri, Jan 20, 2023 at 01:45:43PM +0100, Luca Ellero wrote:
> Controllers that report pressure (e.g. ADS7846) use 5 commands and the
> correct sequence is READ_X, READ_Y, READ_Z1, READ_Z2, PWRDOWN.
>
> Controllers that don't report pressure (e.g. ADS7845/ADS7843) use only 3
> commands and the correct sequence should be READ_X, READ_Y, PWRDOWN. But
> the sequence sent was incorrect: READ_X, READ_Y, READ_Z1.
>
> Fix this by setting the third (and last) command to PWRDOWN.

Provide a Fixes: tag?

> Signed-off-by: Luca Ellero <[email protected]>

--
With Best Regards,
Andy Shevchenko