linux-kernel - Re: [PATCHv3 1/1] drm/imx: convey the pixelclk-active and de-active flags from DT to the ipu-di driver

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Message-ID: <1468342148.2796.29.camel@pengutronix.de>
Date:	Tue, 12 Jul 2016 18:49:08 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Lothar Waßmann <LW@...O-electronics.de>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 1/1] drm/imx: convey the pixelclk-active and de-active
 flags from DT to the ipu-di driver

Am Dienstag, den 12.07.2016, 16:39 +0200 schrieb Thierry Reding:
> On Wed, May 25, 2016 at 03:18:16PM +0200, Lothar Waßmann wrote:
> > The 'de-active' and 'pixelclk-active' DT properties are evaluated
> > by of_parse_display_timing() called from  of_get_drm_display_mode(),
> > but later lost in the conversion from videomode.flags to
> > drm_display_mode.flags.
> > Use an open coded version of of_get_drm_display_mode() to get access
> > to these flags and make sure they are passed on to the ipu-di driver.
> > 
> > Changes vs. v2:
> >   - removed patches which have already been applied
> >   - created a drm_bus_flags_from_videomode() helper to prevent code
> >     duplication as suggested by Philipp Zabel
> > 
> > Changes vs. v1:
> >   - rebased on top of https://patchwork.kernel.org/patch/9113791/ as
> >     per Philipp Zabel's request
> > 
> > GIT: [PATCHv2 1/3] drm/imx: imx-ldb: honor 'native-mode' property when
> > GIT: [PATCHv2 2/3] drm/imx: convey the pixelclk-active and de-active flags
> > GIT: [PATCHv2 3/3] drm/imx: remove dead code
> > Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> > ---
> >  drivers/gpu/drm/drm_modes.c            | 20 +++++++++++++++++++-
> >  drivers/gpu/drm/imx/imx-ldb.c          | 15 ++++++++++-----
> >  drivers/gpu/drm/imx/parallel-display.c | 16 +++++++++++++---
> >  include/drm/drm_modes.h                |  5 +++--
> >  4 files changed, 45 insertions(+), 11 deletions(-)
> 
> Maybe a stupid question, but why does i.MX even allow video timings to
> be specified in DT instead of going through panel drivers like everyone
> else?

DT backwards compatibility. Arguably setting the pixel clock polarity in
DT was always possible, even though it was never hooked up properly in
mainline. We should encourage moving towards panel drivers though. There
are a lot of i.MX6 device trees that could be converted.

regards
Philipp