Re: [RFCv1 11/42] ARM: dts: omap: add channel to DSI panels

From: "H. Nikolaus Schaller" <hns@goldelico.com>
To: Sebastian Reichel <sebastian.reichel@collabora.com>
Cc: kernel@collabora.com, Tony Lindgren <tony@atomide.com>,
	Merlijn Wajer <merlijn@wizzup.org>,
	dri-devel@lists.freedesktop.org,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	linux-omap@vger.kernel.org
Subject: Re: [RFCv1 11/42] ARM: dts: omap: add channel to DSI panels
Date: Mon, 18 Nov 2019 15:37:12 +0100	[thread overview]
Message-ID: <7CBD93FA-60AB-4313-BF9C-230BDE2DAE7D@goldelico.com> (raw)
In-Reply-To: <20191118143332.nyyr6hb4b5c34xew@earth.universe>

> Am 18.11.2019 um 15:33 schrieb Sebastian Reichel <sebastian.reichel@collabora.com>:
> 
> Hi,
> 
> On Mon, Nov 18, 2019 at 03:05:07PM +0200, Tomi Valkeinen wrote:
>> On 17/11/2019 04:39, Sebastian Reichel wrote:
>>> The standard binding for DSI requires, that the channel number
>>> of the panel is encoded in DT. This adds the channel number in
>>> all OMAP3-5 boards, in preparation for using common infrastructure.
>>> 
>>> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
>>> ---
>>>  .../devicetree/bindings/display/panel/panel-dsi-cm.txt      | 4 +++-
>>>  arch/arm/boot/dts/omap3-n950.dts                            | 3 ++-
>>>  arch/arm/boot/dts/omap3.dtsi                                | 3 +++
>>>  arch/arm/boot/dts/omap4-droid4-xt894.dts                    | 3 ++-
>>>  arch/arm/boot/dts/omap4-sdp.dts                             | 6 ++++--
>>>  arch/arm/boot/dts/omap4.dtsi                                | 6 ++++++
>>>  arch/arm/boot/dts/omap5.dtsi                                | 6 ++++++
>>>  7 files changed, 26 insertions(+), 5 deletions(-)
>> 
>> Is this required only in the .txt, or also by the driver? This does break
>> backward compatibility with the dtbs, and there's always someone who won't
>> like it.
> 
> I add a compatible string for the Droid 4 panel in addition to the
> generic one, which is not really required and just a precaution in
> case we need some quirks in the future.
> 
> But I had to add the DSI channel to DT, which is required to follow
> the standard DSI bindings. We cannot use the generic infrastructure
> without this change. Technically it should have been there all the
> time, it is only working because it is currently hardcoded to 0 in
> the panel driver.

Is it possible to change it to default to channel <0> if reg is not
specified?

> 
> TLDR: Yes, it is required by the driver and it does break backward
> compatibility for N950 (panel does not yet work on mainline, since
> the OMAP3 quirks are missing in the omapdrm DSI code), omap4-sdp (
> untested, I do not know if its working) and Droid 4 (known to be
> working with current mainline code, most likely people update their
> DT anyways).
> 
> -- Sebastian

BR,
Nikolaus

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