linux-kernel - Re: [PATCH v2 0/3] drm: introduce bus

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Message-ID: <653e3f9d2d561a166a1768add0c59422@agner.ch>
Date:	Tue, 23 Feb 2016 15:30:03 -0800
From:	Stefan Agner <stefan@...er.ch>
To:	dri-devel@...ts.freedesktop.org, thierry.reding@...il.com
Cc:	airlied@...ux.ie, daniel.vetter@...ll.ch,
	jianwei.wang.chn@...il.com, alison.wang@...escale.com,
	meng.yi@....com, linux@....linux.org.uk, p.zabel@...gutronix.de,
	denis@...rea.com, eric@...rea.com, ville.syrjala@...ux.intel.com,
	linux-kernel@...r.kernel.org, manfred.schlaegl@....at,
	tomi.valkeinen@...com, linux@....linux.org.uk,
	boris.brezillon@...e-electrons.com
Subject: Re: [PATCH v2 0/3] drm: introduce bus_flags for pixel clock polarity

Any comments on this?

Also added Manfred, Tomi and Boris to CC which previously attended in
similar discussions.

Previous discussions:
http://thread.gmane.org/gmane.linux.kernel.api/12830
http://thread.gmane.org/gmane.comp.video.dri.devel/96240/

I think one of the main observation so far was that the pixel clock
polarity is not a property of the mode, and therefor does not fit into
the DRM_MODE_FLAG. This has been pointed out nicely by Russel:
http://thread.gmane.org/gmane.comp.video.dri.devel/96240/focus=96260

Embedded displays connected through parallel bus make use of the
bus_formats field in drm_display_mode. This field defines what kind of
bus format the display requires. This patch follows that idea and adds
bus_flags. bus_flags can be used to define specific bus properties
required by the display, such as pixel clock or data enable polarity...


On 2016-02-08 13:57, Stefan Agner wrote:
> Hi,
> 
> This is a new & split out version of the last patch of my
> "drm/fsl-dcu: fixes and enhancements" patchset:
> https://lkml.org/lkml/2015/11/18/949
> 
> Instead of using struct drm_display_mode to convey the pixel clock
> polarity information, this patchset introduces a new field called
> bus_flags stored in struct drm_display_info.

Note that this solution has been briefly discussed on IRC:
https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&highlight_names=&date=2016-02-08

--
Stefan

> 
> Changes since v1:
> - Introduce bus_flags to convey the pixel clock polarity from
>   panel-simple.c to the driver.
> 
> Stefan Agner (3):
>   drm/fsl-dcu: use mode flags for hsync/vsync polarity
>   drm: introduce bus_flags in drm_display_info
>   drm/fsl-dcu: use bus_flags for pixel clock polarity
> 
>  drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c | 16 +++++++++++++---
>  drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h  |  4 ++--
>  drivers/gpu/drm/panel/panel-simple.c       |  6 +++++-
>  include/drm/drm_crtc.h                     |  9 +++++++++
>  4 files changed, 29 insertions(+), 6 deletions(-)