Re: [PATCH] pinctrl: cherryview: Preserve CHV_PADCTRL1_INVRXTX_TXDATA flag on GPIOs

[Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>]

On Fri, Sep 04, 2020 at 07:21:41PM +0200, Hans de Goede wrote:
> One some devices the GPIO should output the inverted value from what
> device-drivers / ACPI code expects. The reason for this is unknown,
> perhaps these systems use an external buffer chip on the GPIO which
> inverts the signal. The BIOS makes this work by setting the
> CHV_PADCTRL1_INVRXTX_TXDATA flag.
> 
> Before this commit we would unconditionally clear all INVRXTX flags,
> including the CHV_PADCTRL1_INVRXTX_TXDATA flag when a GPIO is requested
> by a driver (from chv_gpio_request_enable()).
> 
> This breaks systems using this setup. Specifically it is causing
> problems for systems with a goodix touchscreen, where the BIOS sets the
> INVRXTX_TXDATA flag on the GPIO used for the touchscreen's reset pin.
> 
> The goodix touchscreen driver by defaults configures this pin as input
> (relying on the pull-up to keep it high), but the clearing of the
> INVRXTX_TXDATA flag done by chv_gpio_request_enable() causes it to be
> driven low for a brief time before the GPIO gets set to input mode.
> 
> This causes the touchscreen controller to get reset. On most CHT devs
> with this touchscreen this leads to:
> 
> [   31.596534] Goodix-TS i2c-GDIX1001:00: i2c test failed attempt 1: -121
> 
> The driver retries this though and then everything is fine. But during
> reset the touchscreen uses its interrupt pin as bootstrap to determine
> which i2c address to use and on the Acer One S1003 the spurious reset
> caused by the clearing of the INVRXTX_TXDATA flag causes the controller
> to come back up again on the wrong i2c address, breaking things.
> 
> This commit fixes both the -121 errors, as well as the total breakage
> on the Acer One S1003, by making chv_gpio_clear_triggering() not clear
> the INVRXTX_TXDATA flag if the pin is already configured as a GPIO.
> 
> Note that chv_pinmux_set_mux() does still unconditionally clear the
> flag, so this only affects GPIO usage.
> 
> Fixes: a7d4b171660c ("Input: goodix - add support for getting IRQ + reset GPIOs on Cherry Trail devices")
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>

Acked-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>