On Mon, May 03, 2021 at 08:21:48PM +0200, Werner Sembach wrote:
When encoder validation of a display mode fails, retry with less bandwidth heavy YCbCr420 color mode, if available. This enables some HDMI 1.4 setups to support 4k60Hz output, which previously failed silently.
AMDGPU had nearly the exact same issue. This problem description is therefore copied from my commit message of the AMDGPU patch.
On some setups, while the monitor and the gpu support display modes with pixel clocks of up to 600MHz, the link encoder might not. This prevents YCbCr444 and RGB encoding for 4k60Hz, but YCbCr420 encoding might still be possible. However, which color mode is used is decided before the link encoder capabilities are checked. This patch fixes the problem by retrying to find a display mode with YCbCr420 enforced and using it, if it is valid.
Signed-off-by: Werner Sembach wse@tuxedocomputers.com
From 4ea0c8839b47e846d46c613e38af475231994f0f Mon Sep 17 00:00:00 2001
From: Werner Sembach wse@tuxedocomputers.com Date: Mon, 3 May 2021 16:23:17 +0200 Subject: [PATCH 4/4] Use YCbCr420 as fallback when RGB fails
drivers/gpu/drm/i915/display/intel_hdmi.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c index e2553ac6fd13..20c800f2ed60 100644 --- a/drivers/gpu/drm/i915/display/intel_hdmi.c +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c @@ -1913,7 +1913,7 @@ intel_hdmi_mode_valid(struct drm_connector *connector, clock *= 2; }
- if (connector->ycbcr_420_allowed && drm_mode_is_420_only(&connector->display_info, mode))
- if (connector->ycbcr_420_allowed && drm_mode_is_420(&connector->display_info, mode)) clock /= 2;
This is too early. We want to keep clock as is for checking whether RGB output is possible with 420_also modes.
So the structure you had in your original patch was the correct way to go about it. Which I think was something along the lines of:
if (420_only) clock /= 2;
status = intel_hdmi_mode_clock_valid() if (status != OK) { if (420_only || !420_also || !420_allowed) return status; clock /= 2; status = intel_hdmi_mode_clock_valid() }
status = intel_hdmi_mode_clock_valid(hdmi, clock, has_hdmi_sink); @@ -2119,6 +2119,14 @@ int intel_hdmi_compute_output_format(struct intel_encoder *encoder, crtc_state->output_format = INTEL_OUTPUT_FORMAT_RGB;
ret = intel_hdmi_compute_clock(encoder, crtc_state);
- if (ret) {
if (crtc_state->output_format != INTEL_OUTPUT_FORMAT_YCBCR420 ||connector->ycbcr_420_allowed ||drm_mode_is_420_also(&connector->display_info, adjusted_mode)) {
That needs s/||/&&/ or we flip the conditions around to:
if (ret) { if (output_format == 420 || !420_allowed || !420_also) return ret;
output_format = 420; ... }
which would have the benefit of avoiding the extra indent level.
crtc_state->output_format = INTEL_OUTPUT_FORMAT_YCBCR420;ret = intel_hdmi_compute_clock(encoder, crtc_state);}}
return ret;
}
2.25.1