Re: [PATCH v2 2/2] Input: atmel_mxt_ts - wake mXT1386 from deep-sleep mode

From: Wang, Jiada
Date: Fri Sep 18 2020 - 11:55:13 EST

Hi Dmitry

Thanks for your quick comments

On 2020/09/18 22:32, Dmitry Osipenko wrote:
18.09.2020 15:56, Jiada Wang пишет:
According to datasheet, mXT1386 chip has a WAKE line, it is used
to wake the chip up from deep sleep mode before communicating with
it via the I2C-compatible interface.

if the WAKE line is connected to a GPIO line, the line must be
asserted 25 ms before the host attempts to communicate with the mXT1386.
If the WAKE line is connected to the SCL pin, the mXT1386 will send a
NACK on the first attempt to address it, the host must then retry 25 ms

This patch introduces mxt_wake() which does a dummy i2c read, follows
with a 25 ms sleep for mXT1386 chip. mxt_wake() is added to
mxt_initialize(), mxt_load_fw() and mxt_start() to ensure before any
actual i2c transfer, mxt_wake() can be executed.

Added new compatible string "atmel,mXT1386".

Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>

Hello, Jiada!

This not critical, but yours suggested-by tag always should be the last
line of the commit message. It's like you're signing all the words that
were written by you.

Suggested-by: Dmitry Osipenko <digetx@xxxxxxxxx>
drivers/input/touchscreen/atmel_mxt_ts.c | 27 ++++++++++++++++++++++++
1 file changed, 27 insertions(+)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index a2189739e30f..d580050a237f 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -196,6 +196,7 @@ enum t100_type {
#define MXT_CRC_TIMEOUT 1000 /* msec */
#define MXT_FW_RESET_TIME 3000 /* msec */
#define MXT_FW_CHG_TIMEOUT 300 /* msec */
+#define MXT_WAKEUP_TIME 25 /* msec */
/* Command to unlock bootloader */
#define MXT_UNLOCK_CMD_MSB 0xaa
@@ -2099,12 +2100,33 @@ static void mxt_config_cb(const struct firmware *cfg, void *ctx)
+static void mxt_wake(struct mxt_data *data)
+ struct i2c_client *client = data->client;
+ struct device *dev = &data->client->dev;
+ struct device_node *np = dev->of_node;
+ union i2c_smbus_data dummy;
+ if (!of_device_is_compatible(np, "atmel,mXT1386"))
+ return;
I'm not sure whether you misses the previous answers from Dmitry
Torokhov and Rob Herring, but they suggested to add a new device-tree
property which should specify the atmel,wakeup-method.

I think Rob Herring prefers for the compatible solution than property.

There are 3 possible variants:


Hence we should bail out from mxt_wake() if method is set to NONE or GPIO.

for "GPIO", we still need 25 ms sleep. but rather than a dummy read, WAKE line need to be asserted before sleep.

Perhaps we could even skip the GPIO method entirely by not mentioning it
anywhere, since this method isn't needed for now.

Nevertheless, I think it will be good to add DT compatible for the
"atmel,mXT1386", hence this part is good to me.

+ /* TODO: add WAKE-GPIO support */
+ i2c_smbus_xfer(client->adapter, client->addr,
+ &dummy);

There is no need to sleep if there was no I2C error, meaning that device
wasn't in a deep-sleep mode. Please add a check for the value returned
by i2c_smbus_xfer() and invoke the msleep() only in a case of the I2C
error condition.

OK. will do this

+ msleep(MXT_WAKEUP_TIME);
static int mxt_initialize(struct mxt_data *data)
struct i2c_client *client = data->client;
int recovery_attempts = 0;
int error;
+ mxt_wake(data);
while (1) {

I assume the mxt_wake() should be placed here, since there is a 3
seconds timeout in the end of the while-loop, meaning that device may
get back into deep-sleep on a retry.

Can you elaborate a little more why exit from bootload mode after sleep for 3 second could enter deep-sleep mode.

error = mxt_read_info_block(data);
if (!error)
@@ -2787,6 +2809,8 @@ static int mxt_load_fw(struct device *dev, const char *fn)
if (ret)
goto release_firmware;
+ mxt_wake(data);
if (!data->in_bootloader) {
/* Change to the bootloader mode */
data->in_bootloader = true;
@@ -2928,6 +2952,7 @@ static const struct attribute_group mxt_attr_group = {
static void mxt_start(struct mxt_data *data)
+ mxt_wake(data);

Shouldn't the mxt_wake() be under the MXT_SUSPEND_DEEP_SLEEP switch? The
wake-up should be needed only for waking from deep-sleep mode.
OK, I will move it under MXT_SUSPEND_DEEP_SLEEP


switch (data->suspend_mode) {
@@ -3185,6 +3210,7 @@ static SIMPLE_DEV_PM_OPS(mxt_pm_ops, mxt_suspend, mxt_resume);
static const struct of_device_id mxt_of_match[] = {
{ .compatible = "atmel,maxtouch", },
+ { .compatible = "atmel,mXT1386", },
/* Compatibles listed below are deprecated */
{ .compatible = "atmel,qt602240_ts", },
{ .compatible = "atmel,atmel_mxt_ts", },
@@ -3209,6 +3235,7 @@ static const struct i2c_device_id mxt_id[] = {
{ "atmel_mxt_tp", 0 },
{ "maxtouch", 0 },
{ "mXT224", 0 },
+ { "mXT1386", 0 },
{ }