[Intel-gfx] [PATCH 3/4] drm/dp: start a DPCD based DP sink/branch device quirk database

[Pandiyan, Dhinakaran]

On Thu, 2017-05-18 at 14:10 +0300, Jani Nikula wrote:
> Face the fact, there are Display Port sink and branch devices out there
> in the wild that don't follow the Display Port specifications, or they
> have bugs, or just otherwise require special treatment. Start a common
> quirk database the drivers can query based on the DP device
> identification. At least for now, we leave the workarounds for the
> drivers to implement as they see fit.
> 
> For starters, add a branch device that can't handle full 24-bit main
> link Mdiv and Ndiv main link attributes properly. Naturally, the
> workaround of reducing main link attributes for all devices ended up in
> regressions for other devices. So here we are.
> 
> v2: Rebase on DRM DP desc read helpers
> 
> v3: Fix the OUI memcmp blunder (Clint)
> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> Cc: Clint Taylor <clinton.a.taylor at intel.com>
> Cc: Adam Jackson <ajax at redhat.com>
> Cc: Harry Wentland <harry.wentland at amd.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 52 +++++++++++++++++++++++++++++++++++++++--
>  include/drm/drm_dp_helper.h     | 32 +++++++++++++++++++++++++
>  2 files changed, 82 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 52e0ca9a5bb1..213fb837e1c4 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c

<snip>
> + * enum drm_dp_quirk - Display Port sink/branch device specific quirks
> + *
> + * Display Port sink and branch devices in the wild have a variety of bugs, try
> + * to collect them here. The quirks are shared, but it's up to the drivers to
> + * implement workarounds for them.
> + */
> +enum drm_dp_quirk {
> +	/**
> +	 * @DP_DPCD_QUIRK_LIMITED_M_N:
> +	 *
> +	 * The device requires main link attributes Mdiv and Ndiv to be limited

s/Mdiv/Mvid
s/Ndiv/Nvid

> +	 * to 16 bits.
> +	 */
> +	DP_DPCD_QUIRK_LIMITED_M_N,
> +};