linux-kernel - Re: [PATCH 2/2] drm/panel: Add ilitek ili9341 panel driver

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Date:   Sun, 18 Jul 2021 02:31:48 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     dillon min <dillon.minfei@...il.com>
Cc:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Dave Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        Doug Anderson <dianders@...omium.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/panel: Add ilitek ili9341 panel driver

Hi Dillon,

thanks for your patch!

On Fri, Jul 16, 2021 at 12:20 PM <dillon.minfei@...il.com> wrote:

> From: Dillon Min <dillon.minfei@...il.com>
>
> This driver combine tiny/ili9341.c mipi_dbi_interface driver
> with mipi_dpi_interface driver, can support ili9341 with serial
> mode or parallel rgb interface mode by register configuration.
>
> Signed-off-by: Dillon Min <dillon.minfei@...il.com>

Nice!

> +config DRM_PANEL_ILITEK_ILI9341
> +       tristate "Ilitek ILI9341 240x320 QVGA panels"
> +       depends on OF && SPI
> +       depends on DRM_KMS_HELPER
> +       depends on DRM_KMS_CMA_HELPER
(...)
> +#include <drm/drm_gem_framebuffer_helper.h>
> +#include <drm/drm_gem_cma_helper.h>
> +#include <drm/drm_fb_helper.h>
> +#include <drm/drm_gem_atomic_helper.h>
> +#include <drm/drm_atomic_helper.h>

Hm now there is a (partial) KMS driver in the panel driver, kinda, sorta.
Is this the right split? I'm not the best with DRM infrastructure,
just asking.

> +struct ili9341_config {
> +       u32 max_spi_speed;
> +       /** @mode: the drm display mode */
> +       const struct drm_display_mode mode;
> +       /* @ca: TODO: need comments for this register */
> +       u8 ca[ILI9341_CA_LEN];

These are all in the datasheet but I guess you plan to add these
TODOs later. (It's fine I suppose, the driver is already very nice.)

> +       struct regulator *vcc;

Use the right name of the pin for the regulator. I guess this is actually
vci. I would implement all three regulators and get them as bulk.
See e.g. drivers/gpu/drm/panel/panel-samsung-s6e3ha2.c
for an example on how to get and enable several regulators
using bulk.

The regulator framework will provide dummy regulators if you
didn't define some of them so it is fine to just provide one or two.

Yours,
Linus Walleij