[Letux-kernel] [REGRESSION] omapdrm/N900 display broken

[H. Nikolaus Schaller]

Hi Ivaylo,

> Am 27.11.2020 um 19:44 schrieb Ivaylo Dimitrov <ivo.g.dimitrov.75 at gmail.com>:
> 
> Hi,
> 
> On 27.11.20 г. 19:30 ч., Tomi Valkeinen wrote:
>> On 27/11/2020 17:37, Ivaylo Dimitrov wrote:
>>> With 5.9.11 and the patch on top, n900 boots fine, albeit display remains blank, could be related to
>>> brightness, we're still investigating.
>> Ok. A DSS regdump for a working version and the latest one would be good too. There's a omapdss
>> debugfs dir, with dss, dispc and clk files which are of interest here.
> 
> It turned out to be a long standing bug in the panel driver, with the bellow fix it works fine:
> 
> 
> diff --git a/drivers/gpu/drm/panel/panel-sony-acx565akm.c b/drivers/gpu/drm/panel/panel-sony-acx565akm.c
> index fc6a7e451abe..304267f7849a
> --- a/drivers/gpu/drm/panel/panel-sony-acx565akm.c
> +++ b/drivers/gpu/drm/panel/panel-sony-acx565akm.c
> @@ -629,7 +629,7 @@ static int acx565akm_probe(struct spi_device *spi)
>        lcd->spi = spi;
>        mutex_init(&lcd->mutex);
> 
> -       lcd->reset_gpio = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_LOW);
> +       lcd->reset_gpio = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_HIGH);
>        if (IS_ERR(lcd->reset_gpio)) {
>                dev_err(&spi->dev, "failed to get reset GPIO\n");
>                return PTR_ERR(lcd->reset_gpio);
> 
> Proper patch will follow.

I just found another issue which seems to hit a handful of SPI based panel drivers,
for example the panel-tpo-td028ttec1.

It is commit

766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")

which breaks our DM3730 based GTA04 panel drivers/gpu/drm/panel/panel-tpo-td028ttec1.c.
It may also affect other SPI based drivers if they are operated though spi-gpio (I would
have to look up the N900 hardware setup).

BR,
Nikolaus