[RFC][PATCH 0/2] Add mode_valid drm_crtc_helper_funcs for HiKey

[John Stultz]

Currently, on the hikey board, we have the adv7511 bridge wired
up to the kirin ade drm driver. Unfortunately, the kirin ade
core cannot generate accurate byteclocks for all pixel clock
values.

Thus if a mode clock is selected that we cannot calculate a
matching byteclock, the device will boot with a blank screen.

Unfortunately, currently the only place we can properly check
potential modes for this issue in the connector mode_valid
helper. Again, hikey uses the adv7511 bridge, which is shared
between a number of different devices, so its improper to put
restrictions caused by the kirin drm driver in the adv7511
logic.

So this patch set tries to fix this by adding some
infrastructure and logic to the probe helpers so that drm_crtcs
can filter the probed modes. And then adds a whitelist of valid
modes for the kirin drm driver used on HiKey.

This is a first pass attempt here, implementing a suggestion from
Rob Clark on irc, so I'd really welcome any feedback or ideas for
how to best do this.

Thanks so much!
-john

Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Sean Paul <seanpaul at chromium.org>
Cc: David Airlie <airlied at linux.ie>
Cc: Rob Clark <robdclark at gmail.com>
Cc: Xinliang Liu <xinliang.liu at linaro.org>
Cc: Xinliang Liu <z.liuxinliang at hisilicon.com>
Cc: Rongrong Zou <zourongrong at gmail.com>
Cc: Xinwei Kong <kong.kongxinwei at hisilicon.com>
Cc: Chen Feng <puck.chen at hisilicon.com>
Cc: Archit Taneja <architt at codeaurora.org>
Cc: dri-devel at lists.freedesktop.org

John Stultz (2):
  drm/probe-helper: Add mode_valid check to drm_crtc_helper_funcs
  drm: kirin: Restrict modes to known good mode clocks

 drivers/gpu/drm/drm_probe_helper.c              | 24 ++++++++++++++++
 drivers/gpu/drm/hisilicon/kirin/kirin_drm_ade.c | 38 +++++++++++++++++++++++++
 include/drm/drm_modeset_helper_vtables.h        | 26 +++++++++++++++++
 3 files changed, 88 insertions(+)

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2.7.4