linux-kernel - Re: [RFC PATCH 1/2] drm: add support for for clk and de polarity

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Date:	Wed, 25 Nov 2015 18:22:21 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Manfred Schlaegl <manfred.schlaegl@....at>
Cc:	David Airlie <airlied@...ux.ie>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org,
	Manfred Schlaegl <manfred.schlaegl@...zinger.com>,
	Steve Longerbeam <slongerbeam@...il.com>,
	Deepak Das <deepak_das@...tor.com>,
	Jiada Wang <jiada_wang@...tor.com>, linux-fbdev@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] drm: add support for for clk and de polarity

Am Mittwoch, den 15.07.2015, 17:50 +0200 schrieb Manfred Schlaegl:
> To get full support for parallel and LVDS displays with drm:
> Add representation for clock and data enable polarity in drm_display_mode
> flags (similar to HSYNC/VSYNC polarity) and update conversion functions
> from/to videomode accordingly.
> 
> This is especially important for embedded devices where parallel(RGB) and
> LVDS displays are still widely used and drm already plays an important
> role.
> 
> Tested on Freescale i.MX53(parallel) and i.MX6(LVDS).
> 
> Background:
> There was the ability to set polarity of clock and data enable signals
> in devicetree(display-timing), struct display_timing and struct videomode,
> but there was no representation for this in struct drm_display_mode.
> Example on Freescale i.MX53/i.MX6 SoC's:
>  * A parallel display using different clock polarity is set up using
>    display-timing in devicetree
>  * ipuv3 parallel outputs clock with wrong polarity
> 
> Signed-off-by: Manfred Schlaegl <manfred.schlaegl@....at>

Any comments on whether data enable and pixel clock polarity flags can
be added to the visible DRM_MODE_FLAGs, and if not, where else this
information should be kept? struct drm_display_info?

This patch and the following IPUv3 patch are useful and necessary for
quite some panels connected to i.MX SoCs, but adding DRM_MODE_FLAGs is
somewhat out of my jurisdiction.

best regards
Philipp

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