linux-kernel - [PATCH 0/2] Fix st7703 panel initialization failures

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Date:   Thu, 16 Jul 2020 14:37:51 +0200
From:   Ondrej Jirman <megous@...ous.com>
To:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Fabio Estevam <festevam@...il.com>,
        Guido Günther <agx@...xcpu.org>,
        Robert Chiras <robert.chiras@....com>
Cc:     Ondrej Jirman <megous@...ous.com>,
        Samuel Holland <samuel@...lland.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] Fix st7703 panel initialization failures

When extending the driver for xbd599 panel support I tried to do minimal
changes and keep the existing initialization timing.

It turned out that it's not good enough and the existing init sequence
is too aggressive and doesn't follow the specification. On PinePhone
panel is being powered down/up during suspend/resume and with current
timings this frequently leads to corrupted display.

This patch series fixes the problems.

The issue was reported by Samuel Holland.

Relevant screenshots from the datasheet:

  Power on timing: https://megous.com/dl/tmp/35b72e674ce0ca27.png
  Power off timing: https://megous.com/dl/tmp/dea195517106ff17.png
  More optimal reset on poweron: https://megous.com/dl/tmp/a9e5caf14e1b0dc6.png
  Less optimal reset on poweron: https://megous.com/dl/tmp/246761039283c4cf.png
  Datasheet: https://megous.com/dl/tmp/ST7703_DS_v01_20160128.pdf

Please take a look.

thank you and regards,
  Ondrej Jirman

Ondrej Jirman (2):
  drm/panel: st7703: Make the sleep exit timing match the spec
  drm/panel: st7703: Fix the power up sequence of the panel

 drivers/gpu/drm/panel/panel-sitronix-st7703.c | 29 ++++++++++---------
 1 file changed, 15 insertions(+), 14 deletions(-)

-- 
2.27.0