On Fri, 27 Mar 2020, Vipin Anand <vipin.anand@xxxxxxxxx> wrote:
> From: Uma Shankar <uma.shankar@xxxxxxxxx>
>
> Blanking needs to be reduced to incorporate DP and HDMI timing/link
> bandwidth limitations for CEA modes (4k@60 at 10 bpp). DP can drive
> 17.28Gbs while 4k modes (VIC97 etc) at 10 bpp required 17.8 Gbps.
> This will cause mode to blank out. Reduced Htotal by shortening the
> back porch and front porch within permissible limits.
>
> v2: This is marked as Not for merge and the responsibilty to program
> these custom timings will be on userspace. This patch is just for
> reference purposes. This is based on Ville's recommendation.
This must be highlighted in the subject. HACK or whatever.
And even as a hack, don't change stuff in the .mode_valid hook. It
belongs to compute config.
BR,
Jani.
>
> Signed-off-by: Uma Shankar <uma.shankar@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index c7424e2a04a3..3ab1fadb2ea3 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -616,9 +616,11 @@ intel_dp_mode_valid(struct drm_connector *connector,
> {
> struct intel_dp *intel_dp = intel_attached_dp(to_intel_connector(connector));
> struct intel_connector *intel_connector = to_intel_connector(connector);
> + struct intel_encoder *intel_encoder = intel_attached_encoder(intel_connector);
> struct drm_display_mode *fixed_mode = intel_connector->panel.fixed_mode;
> struct drm_i915_private *dev_priv = to_i915(connector->dev);
> int target_clock = mode->clock;
> + struct intel_lspcon *lspcon = enc_to_intel_lspcon(intel_encoder);
> int max_rate, mode_rate, max_lanes, max_link_clock;
> int max_dotclk;
> u16 dsc_max_output_bpp = 0;
> @@ -638,6 +640,20 @@ intel_dp_mode_valid(struct drm_connector *connector,
>
> target_clock = fixed_mode->clock;
> }
> + /*
> + * Reducing Blanking to incorporate DP and HDMI timing/link bandwidth
> + * limitations for CEA modes (4k@60 at 10 bpp). DP can drive 17.28Gbs
> + * while 4k modes (VIC97 etc) at 10 bpp required 17.8 Gbps. This will
> + * cause mode to blank out. Reduced Htotal by shortening the back porch
> + * and front porch within permissible limits.
> + */
> + if (lspcon->active && lspcon->hdr_supported &&
> + mode->clock > 570000) {
> + mode->clock = 570000;
> + mode->htotal -= 180;
> + mode->hsync_start -= 72;
> + mode->hsync_end -= 72;
> + }
>
> max_link_clock = intel_dp_max_link_rate(intel_dp);
> max_lanes = intel_dp_max_lane_count(intel_dp);
--
Jani Nikula, Intel Open Source Graphics Center
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