linux-kernel - Re: [PATCH v3 2/3] dt-bindings: Add header for the ingenic-drm driver bindings

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Message-Id: <1555949582.1483.0@crapouillou.net>
Date:   Mon, 22 Apr 2019 18:13:02 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:     Rob Herring <robh+dt@...nel.org>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, od@...c.me,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] dt-bindings: Add header for the ingenic-drm driver
 bindings

Hi,

Le sam. 20 avril 2019 à 14:23, Ezequiel Garcia 
<ezequiel@...guardiasur.com.ar> a écrit :
> On Wed, 17 Apr 2019 at 10:48, Rob Herring <robh+dt@...nel.org> wrote:
>> 
>>  On Sun, Apr 14, 2019 at 3:08 PM Paul Cercueil 
>> <paul@...pouillou.net> wrote:
>>  >
>>  > Add macros that can be used with the ingenic,lcd-mode property in 
>> the
>>  > devicetree node that corresponds to the ingenic-drm driver.
>> 
>>  DRM is a Linuxism.
>> 
>>  >
>>  > Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>  > Tested-by: Artur Rojek <contact@...ur-rojek.eu>
>>  > ---
>>  >
>>  > Notes:
>>  >     v2: No change
>>  >
>>  >     v3: s/_DRM//
>>  >
>>  >  include/dt-bindings/display/ingenic,drm.h | 28 
>> ++++++++++++++++++++++++++++
>> 
>>  DRM is a Linuxism...
>> 
>>  >  1 file changed, 28 insertions(+)
>>  >  create mode 100644 include/dt-bindings/display/ingenic,drm.h
>>  >
>>  > diff --git a/include/dt-bindings/display/ingenic,drm.h 
>> b/include/dt-bindings/display/ingenic,drm.h
>>  > new file mode 100644
>>  > index 000000000000..c749b8c346fc
>>  > --- /dev/null
>>  > +++ b/include/dt-bindings/display/ingenic,drm.h
>>  > @@ -0,0 +1,28 @@
>>  > +/* SPDX-License-Identifier: GPL-2.0 */
>>  > +/*
>>  > + *  Ingenic JZ47xx KMS driver
>> 
>>  Pretty sure this file is not a KMS driver.
>> 
>>  > + *
>>  > + *  Copyright (C) 2019, Paul Cercueil <paul@...pouillou.net>
>>  > + */
>>  > +#ifndef __INCLUDE_DT_BINDINGS_DISPLAY_INGENIC_DRM_H__
>>  > +#define __INCLUDE_DT_BINDINGS_DISPLAY_INGENIC_DRM_H__
>>  > +
>>  > +#define JZ_LCD_GENERIC_16BIT                   0
>>  > +#define JZ_LCD_GENERIC_18BIT                   16
>> 
>>  We have some generic properties for defining the bus width already.
>>  Plus, in many cases this can be implied by the panel compatible. The
>>  exceptions are cases such as when both the ctrlr and panel support
>>  multiple modes.
>> 
> 
> In the same direction as Rob's comment, I'd like to see these 
> decoupled
> from the register value.
> 
> Ideally, we'd like to reuse this driver and its bindings for JZ4780,
> and these values are already different.

Well they are not any different on the JZ4780, I just checked on the 
manual.
But yes, I don't mind getting rid of that devicetree property and its
corresponding bindings file.

The major problem is that we don't have a way to map some of the values 
there
to DRM macros. I sumitted a PR to add a MEDIA_BUS_FMT_RGB888_3X8_BE bus 
format
(that I could detect to support 8-bit serial TFT panels, which is what 
the
Ben Nanonote uses), but I miss a way to detect the special* TFT panels.
I will leave these aside for now, but I want to support them eventually.

Thanks,
-Paul

* "special" TFT panels have extra pins (CLS, SPL, REV, PS) and seem to 
be a
thing from Sharp. Ingenic SoCs (as well as i.MX SoCs) have the required
hardware to drive these panels.

> Thanks!
> --
> Ezequiel García, VanguardiaSur
> www.vanguardiasur.com.ar