[PATCH v3 0/3] ads7846: fix support for ADS7845

[PATCH v3 0/3] ads7846: fix support for ADS7845

[Luca Ellero]

ADS7845 support is buggy in this driver.
These patches fix various issues to get it work properly.

Changes for v2:
 - add missing period in patch 0001 message
 - elaborate comment in patch 0002
 
Changes for v3:
 - send from the same email address of "Signed-off"

Luca Ellero (3):
  ads7846: don't report pressure for ads7845
  ads7846: always set last command to PWRDOWN
  ads7846: don't check penirq immediately for 7845

 drivers/input/touchscreen/ads7846.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

-- 
2.25.1

[PATCH v3 1/3] ads7846: don't report pressure for ads7845

[Luca Ellero]

ADS7845 doesn't support pressure.
This patch avoids the following error reported by libinput-list-devices:
"ADS7845 Touchscreen: kernel bug: device has min == max on ABS_PRESSURE".

Signed-off-by: Luca Ellero <l.ellero@asem.it>
---
 drivers/input/touchscreen/ads7846.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index bed68a68f330..24605c40d039 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -1316,8 +1316,9 @@ static int ads7846_probe(struct spi_device *spi)
 			pdata->y_min ? : 0,
 			pdata->y_max ? : MAX_12BIT,
 			0, 0);
-	input_set_abs_params(input_dev, ABS_PRESSURE,
-			pdata->pressure_min, pdata->pressure_max, 0, 0);
+	if (ts->model != 7845)
+		input_set_abs_params(input_dev, ABS_PRESSURE,
+				pdata->pressure_min, pdata->pressure_max, 0, 0);
 
 	/*
 	 * Parse common framework properties. Must be done here to ensure the
-- 
2.25.1

[PATCH v3 2/3] ads7846: always set last command to PWRDOWN

[Luca Ellero]

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.

This patch fixes it.

Signed-off-by: Luca Ellero <l.ellero@asem.it>
---
 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 24605c40d039..9e15cdf6faa0 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

[PATCH v3 3/3] ads7846: don't check penirq immediately for 7845

[Luca Ellero]

To discard false readings, one should use "ti,penirq-recheck-delay-usecs".
Checking get_pendown_state() at the beginning, most of the time fails
causing malfunctioning.

Signed-off-by: Luca Ellero <l.ellero@asem.it>
---
 drivers/input/touchscreen/ads7846.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 9e15cdf6faa0..122d3a13b7c5 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -843,14 +843,8 @@ static void ads7846_report_state(struct ads7846 *ts)
 	if (x == MAX_12BIT)
 		x = 0;
 
-	if (ts->model == 7843) {
+	if (ts->model == 7843 || ts->model == 7845) {
 		Rt = ts->pressure_max / 2;
-	} else if (ts->model == 7845) {
-		if (get_pendown_state(ts))
-			Rt = ts->pressure_max / 2;
-		else
-			Rt = 0;
-		dev_vdbg(&ts->spi->dev, "x/y: %d/%d, PD %d\n", x, y, Rt);
 	} else if (likely(x && z1)) {
 		/* compute touch pressure resistance using equation #2 */
 		Rt = z2;
-- 
2.25.1

Re: [PATCH v3 0/3] ads7846: fix support for ADS7845

[Andy Shevchenko]

On Fri, Aug 12, 2022 at 10:42:45AM +0200, Luca Ellero wrote:
> ADS7845 support is buggy in this driver.
> These patches fix various issues to get it work properly.

Don't remember if I given a tag already (note, it's contributor's
responsibility to carry tags if received), so here it is:

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Changes for v2:
>  - add missing period in patch 0001 message
>  - elaborate comment in patch 0002
>  
> Changes for v3:
>  - send from the same email address of "Signed-off"
> 
> Luca Ellero (3):
>   ads7846: don't report pressure for ads7845
>   ads7846: always set last command to PWRDOWN
>   ads7846: don't check penirq immediately for 7845
> 
>  drivers/input/touchscreen/ads7846.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> -- 
> 2.25.1
> 

-- 
With Best Regards,
Andy Shevchenko