linux-kernel - Re: [PATCH 21/21] panel: startek-kd070fhfid015: add support of this display

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Date:   Wed, 15 Mar 2023 16:59:29 +0100
From:   Alexandre Mergnat <amergnat@...libre.com>
To:     neil.armstrong@...aro.org
Cc:     Daniel Vetter <daniel@...ll.ch>, CK Hu <ck.hu@...iatek.com>,
        Jitao Shi <jitao.shi@...iatek.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sam Ravnborg <sam@...nborg.org>,
        Rob Herring <robh+dt@...nel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        David Airlie <airlied@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Xinlei Lee <xinlei.lee@...iatek.com>,
        Guillaume La Roque <glaroque@...libre.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org,
        Fabien Parent <fparent@...libre.com>,
        linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 21/21] panel: startek-kd070fhfid015: add support of this display

Hi Neil,

Le jeu. 9 mars 2023 à 15:51, Neil Armstrong
<neil.armstrong@...aro.org> a écrit :
> > +
> > +#include <drm/drm_crtc.h>
>
> Is this include needed ?

Seems not, I remove it.

> > +     struct gpio_desc *enable_gpio;
> > +     struct gpio_desc *reset_gpio;
> > +     struct gpio_desc *dcdc_en_gpio;
>
> Isn't this "DCDC" a regulator ???

According to the panel datasheet, this is an input signal needed
passing through TFT connector (PIN30):
"Power IC supply enable, High active"

> > +     /* Interface setting, video mode */
> > +     ret = mipi_dsi_generic_write(dsi,
> > +                     (u8[]){DSI_REG_IS, 0x14, 0x08, 0x00, 0x22, 0x00}, 6);
> > +     if (ret < 0) {
> > +             dev_err(dev, "failed to set display interface setting: %d\n",
> > +                     ret);
> > +             return ret;
> > +     }
>
> Use mipi_dsi_generic_write_seq(dsi, DSI_REG_IS, 0x14, 0x08, 0x00, 0x22, 0x00); instead,
> it's simpler and doesn't need explicit return check.

"mipi_dsi_generic_write_seq" doesn't exist but I will add it below
"mipi_dsi_dcs_write_seq" in drm_mipi_dsi.h
I must keep the return check to jump out of "stk_panel_init" if
something goes wrong, but I can drop the error print.

> > +static int stk_panel_enable(struct drm_panel *panel)
> > +{
> > +     struct stk_panel *stk = to_stk_panel(panel);
> > +
> > +     if (stk->enabled)
> > +             return 0;
> > +
> > +     backlight_enable(stk->backlight);
> > +
> > +     stk->enabled = true;
> > +
> > +     return 0;
> > +}
>
> Is this really needed ? the backlight core will enable it automatically.

Ok, it's managed by drm_panel.c driver.
Then I can also remove stuff from stk_panel_disable.


Regards,
Alex