linux-kernel - Re: [PATCH 00/23] Nokia N950 display support

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Date:	Wed, 9 Mar 2016 09:10:28 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Sebastian Reichel <sre@...nel.org>,
	Aaro Koskinen <aaro.koskinen@....fi>
CC:	Tony Lindgren <tony@...mide.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Airlie <airlied@...ux.ie>, <linux-omap@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/23] Nokia N950 display support

On 08/03/16 22:45, Sebastian Reichel wrote:
> Hi,
> 
> On Tue, Mar 08, 2016 at 08:39:08PM +0200, Aaro Koskinen wrote:
>> On Tue, Mar 08, 2016 at 05:39:32PM +0100, Sebastian Reichel wrote:
>>> This series adds support for the Nokia N950 display.
>>> Since the panel is using DSI command mode, it involves
>>> adding support for manually updated displays to
>>> omapdrm.
>>
>> Works OK, but the picture seems to be upside down?
> 
> vertical, upside down is the native panel orientation.
> 
>> Also shouldn't the default orientation be landscape?
> 
> The N950 vendor kernel contains some code adding DSI
> rotation support with half-frame update mechnism to
> avoid tearing. It's quite complex and as far as I
> understand it also error-prone. Tomi knows more about
> that.

It needs support in both the panel driver and the dispc driver, and is
quite intrusive. Or, at least it was with omapfb, I can't say if it
could somehow be implemented more cleanly with omapdrm. It's definitely
not something I will be working on.

> I have a simpler patch without the half-frame update
> stuff, which works fine for me. I didn't notice any
> tearing, but I haven't done any really fast image

You will see diagonal tearing with that rotation. But maybe that's not
an issue. I think it's the best option available if landscape mode is
required.

> updating. Also omapdrm has rotation support using
> the DSS hardware, which also seems to work ok. I'm
> still checking out what method is most suitable for
> mainline.

Hmm there's only so called DMA rotation, which shouldn't work. It's only
meant for really small displays, when the framebuffer is in SRAM. So I'm
a bit baffled as to what rotation you are using and why is it working =).

There is also VRFB rotation on omap3, but that's not supported by omapdrm.

> But yeah, we probably want to change the default
> rotation. Especially since touchscreen should have
> the same default rotation as the screen. (TS is
> horizontal, correct orientation for keyboard usage)

I don't know much about touchscreens, but I'm guessing that it's easier
to rotate the coordinates from touch than achieve good panel rotation on
N950.

 Tomi

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