On 2015-11-25 18:22, Philipp Zabel wrote:

Am Mittwoch, den 15.07.2015, 17:50 +0200 schrieb Manfred Schlaegl:

quoted

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 <redacted>

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

Good to see that this discussion is triggered.

State of the sent patches respective to git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git (78c4a49)
 * [RFC PATCH 1/2] drm: add support for for clk and de polarity
   * applies unmodified
 * [RFC PATCH 2/2] gpu: ipu-v3: use clock and de polarity from videomode
   * does not apply -> but this can be fixed with corrections of line offsets (using patch)
From a code review I think the modifications must work, but I did no testing on kernel versions newer than 4.1.13.
On demand, I can redo tests on some of our i.MX53 (parallel) and i.MX6 (lvds) boards and send actual patches.

best regards,
Manfred

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