linux-kernel - Re: [PATCH v2 3/3] drm/panel: Add ilitek ili9341 panel driver

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Message-ID: <1e4743b0-250f-975a-f83d-5d000c6496e3@tronnes.org>
Date:   Thu, 22 Jul 2021 09:03:41 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Dillon Min <dillon.minfei@...il.com>
Cc:     Thierry Reding <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>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre TORGUE <alexandre.torgue@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Doug Anderson <dianders@...omium.org>,
        linux-stm32@...md-mailman.stormreply.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "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 Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] drm/panel: Add ilitek ili9341 panel driver



Den 22.07.2021 04.07, skrev Dillon Min:
> Hi Noralf
> 
> Thanks for your time to review my patch.
> 
> On Thu, 22 Jul 2021 at 01:42, Noralf Trønnes <noralf@...nnes.org> wrote:
>>
>>
>>
>> Den 21.07.2021 09.41, skrev dillon.minfei@...il.com:
>>> 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.
>>>
>>> Cc: Linus Walleij <linus.walleij@...aro.org>
>>> Signed-off-by: Dillon Min <dillon.minfei@...il.com>
>>> ---
>>
>>> +static const struct of_device_id ili9341_of_match[] = {
>>> +     {
>>> +             .compatible = "st,sf-tc240t-9370-t",
>>> +             .data = &ili9341_stm32f429_disco_data,
>>> +     },
>>> +     {
>>> +             /* porting from tiny/ili9341.c
>>> +              * for original mipi dbi compitable
>>> +              */
>>> +             .compatible = "adafruit,yx240qv29",
>>
>> I don't understand this, now there will be 2 drivers that support the
>> same display?
> 
> There is no reason to create two drivers to support the same display.
> 
> To support only-dbi and dbi+dpi panel at drm/panel or drm/tiny both
> fine with me.
> 
>>
>> AFAICT drm/tiny/ili9341.c is just copied into this driver, is the plan
>> to remove the tiny/ driver? If so I couldn't see this mentioned anywhere.
> 
> Yes, I'd like to merge the code from drm/tiny/ili9341.c to this driver
> (to make a single driver to support different bus).
> 
> I have two purpose to extend the feature drm/tiny/ili9341.c
> 
> - keep compatible = "adafruit,yx240qv29", add bus mode dts bindings (panel_bus)
>   to define the interface which host wants to use. such as
> panel_bus="dbi" or "rgb"
>   or "i80" for this case, i will add dpi code to drm/tiny/ili9341.c.
> 
> - merge tiny/ili9341.c to this driver,remove drm/tiny/ili9341.c, add
> new dts compatible
>   string to support other interfaces. just like what i'm doing now.
> 
> I have no idea about your plan on drm/tiny drivers, actually some of
> these panels under
> the diny folder can support both dbi and dbi+dpi (much faster, need
> more pins). no
> doubt the requirement to support dpi is always there.
> 
> What is your preference?
> 

I have no plans for tiny/, it's just a place to put tiny DRM drivers of
all sorts.

Whether or not to have "full" DRM drivers in panel/ is up to Sam and
Laurent I guess, currently there's only drm_panel drivers in there. I
have no objections to doing that though.

I just wanted to make sure we don't have 2 drivers for the same display.

Noralf.

> Thanks & Regards
> Dillon
> 
>>
>> Noralf.
>>
>>> +             .data = NULL,
>>> +     },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, ili9341_of_match);