[PATCH 5.15 117/245] Input: ads7846 - always set last command to PWRDOWN

Greg Kroah-Hartman
2024-02-27T14:06:19Z

From: Luca Ellero <l.ellero@asem.it>

[ Upstream commit 13f82ca3878db8284a70ef9711d7f710a31eb562 ]

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.

Fixes: ffa458c1bd9b ("spi: ads7846 driver")
Signed-off-by: Luca Ellero <l.ellero@asem.it>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230126105227.47648-3-l.ellero@asem.it
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 ef04988edf0c2..f416a4bcd72bf 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -1074,6 +1074,9 @@ 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
@@ -1110,7 +1113,12 @@ 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;
--
2.43.0