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Input: cyttsp - reduce reset pulse timings 

The data sheet for CY8CTMA340 specifies that the reset pulse shall be at
least 1 ms. Specify 1-2 ms with usleep_range() to cut some slack for the
scheduler.

Curiously the datasheet does not specify how long we have to wait after a
hard reset until the chip is up, but I have found a vendor tree (Samsung
GT-S7710) that has code for this touch screen and there this is set to 5
ms so I use this with the same 1 ms fuzz.

Reviewed-by: Javier Martinez Canillas <javier@dowhile0.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20210408131153.3446138-6-linus.walleij@linaro.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
Linus Walleij 2021-04-10 00:31:52 -07:00 committed by Dmitry Torokhov
parent 3984113676
commit c61ac36fd5
1 changed files with 8 additions and 2 deletions
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10
drivers/input/touchscreen/cyttsp_core.c
View File

@ -229,10 +229,16 @@ static int cyttsp_set_sysinfo_regs(struct cyttsp *ts)
static void cyttsp_hard_reset(struct cyttsp *ts)
{
if (ts->reset_gpio) {
/*
* According to the CY8CTMA340 datasheet page 21, the external
* reset pulse width should be >= 1 ms. The datasheet does not
* specify how long we have to wait after reset but a vendor
* tree specifies 5 ms here.
*/
gpiod_set_value_cansleep(ts->reset_gpio, 1);
msleep(CY_DELAY_DFLT);
usleep_range(1000, 2000);
gpiod_set_value_cansleep(ts->reset_gpio, 0);
msleep(CY_DELAY_DFLT);
usleep_range(5000, 6000);
}
}