Re: [PATCH v3 7/7] drm/i915: Add YCBCR 4:2:0/4:4:4 support for LSPCON

Ville Syrjälä
2018-01-18T14:03:51Z

On Thu, Jan 18, 2018 at 11:57:09AM +0530, Sharma, Shashank wrote:
> Regards
>
> Shashank
>
>
> On 1/17/2018 11:57 PM, Ville Syrjälä wrote:
> > On Fri, Jan 05, 2018 at 03:15:35PM +0530, Shashank Sharma wrote:
> >> LSPCON chips can generate YCBCR outputs, if asked nicely :).
> >>
> >> In order to generate YCBCR 4:2:0 outputs, a source must:
> >> - send YCBCR 4:4:4 signals to LSPCON
> >> - program color space as 4:2:0 in AVI infoframes
> >>
> >> Whereas for YCBCR 4:4:4 outputs, the source must:
> >> - send YCBCR 4:4:4 signals to LSPCON
> >> - program color space as 4:4:4 in AVI infoframes
> >>
> >> So for both 4:2:0 as well as 4:4:4 outputs, we are driving the
> >> pipe for YCBCR 4:4:4 output, but AVI infoframe's color space
> >> information indicates LSPCON FW to start scaling down from YCBCR
> >> 4:4:4 and generate YCBCR 4:2:0 output. As the scaling is done by
> >> LSPCON device, we need not to reserve a scaler for 4:2:0 outputs.
> >>
> >> V2: rebase
> >> V3: Addressed review comments from Ville
> >> - add enum crtc_output_format instead of bool ycbcr420
> >> - use crtc_output_format=4:4:4 for modeset of LSPCON 4:2:0 output
> >> cases in this way we will have YCBCR 4:4:4 framework ready (except
> >> the ABI part)
> >>
> >> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> >> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> >> ---
> >> drivers/gpu/drm/i915/i915_reg.h | 2 ++
> >> drivers/gpu/drm/i915/intel_ddi.c | 7 +++++++
> >> drivers/gpu/drm/i915/intel_dp.c | 10 ++++++++++
> >> drivers/gpu/drm/i915/intel_drv.h | 2 ++
> >> drivers/gpu/drm/i915/intel_lspcon.c | 28 ++++++++++++++++++++++++++++
> >> 5 files changed, 49 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> >> index 966e4df..45ee264 100644
> >> --- a/drivers/gpu/drm/i915/i915_reg.h
> >> +++ b/drivers/gpu/drm/i915/i915_reg.h
> >> @@ -8547,6 +8547,8 @@ enum skl_power_gate {
> >> #define TRANS_MSA_MISC(tran) _MMIO_TRANS2(tran, _TRANSA_MSA_MISC)
> >>
> >> #define TRANS_MSA_SYNC_CLK (1<<0)
> >> +#define TRANS_MSA_SAMPLING_444 (2<<1)
> >> +#define TRANS_MSA_CLRSP_YCBCR (2<<3)
> >> #define TRANS_MSA_6_BPC (0<<5)
> >> #define TRANS_MSA_8_BPC (1<<5)
> >> #define TRANS_MSA_10_BPC (2<<5)
> >> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> >> index 7b89f2a..7616f6f 100644
> >> --- a/drivers/gpu/drm/i915/intel_ddi.c
> >> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> >> @@ -1499,6 +1499,13 @@ void intel_ddi_set_pipe_settings(const struct intel_crtc_state *crtc_state)
> >> break;
> >> }
> >>
> >> + /*
> >> + * As per DP 1.2 spec section 2.3.4.3 while sending
> >> + * YCBCR 444 signals we should program MSA MISC1/0 fields with
> >> + * colorspace information.
> >> + */
> >> + if (crtc_state->output_format == CRTC_OUTPUT_YCBCR444)
> >> + temp |= TRANS_MSA_SAMPLING_444 | TRANS_MSA_CLRSP_YCBCR;
> > This fails to state that we're indicating BT.601 encoding. I think we
> > should spell that out explicitly.
> Agree, I will add this in comments.
> >> I915_WRITE(TRANS_MSA_MISC(cpu_transcoder), temp);
> >> }
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> >> index 35c5299..3bf82ea 100644
> >> --- a/drivers/gpu/drm/i915/intel_dp.c
> >> +++ b/drivers/gpu/drm/i915/intel_dp.c
> >> @@ -1613,6 +1613,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> >> struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >> struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
> >> struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> >> + struct intel_lspcon *lspcon = enc_to_intel_lspcon(&encoder->base);
> >> enum port port = encoder->port;
> >> struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
> >> struct intel_connector *intel_connector = intel_dp->attached_connector;
> >> @@ -1642,6 +1643,15 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> >> if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
> >> pipe_config->has_pch_encoder = true;
> >>
> >> + if (lspcon->active) {
> >> + struct drm_connector *connector = &intel_connector->base;
> >> +
> >> + if (lspcon_ycbcr420_config(connector, pipe_config)) {
> >> + pipe_config->output_format = CRTC_OUTPUT_YCBCR444;
> > I think I'd like to see all compute_config hooks explicitly set the
> > outout_format (to RGB usually obviously).
> That's the one I was talking about in previous patch. If we keep
> output_format_RGB = 0, we need
> not to do this, as reset of the pipe_config will automatically make it RGB.

IMO either we have INVALID=0 so that we use it to catch readout
fails, or we have no INVALID. Other options make little sense to me.

> >> + lspcon->output_format = CRTC_OUTPUT_YCBCR420;
> > You should not modify any non-atomic state like that in compute_config.
> Please help me to understand this better, Can you elaborate a bit more on:
> - Why is this a non-atomic state ?
> - What is the right place we should modify it ?

I don't think you need it at all. Just consult the crtc state when
needed.

>
> - Shashank
> >> + }
> >> + }
> >> +
> >> pipe_config->has_drrs = false;
> >> if (IS_G4X(dev_priv) || port == PORT_A)
> >> pipe_config->has_audio = false;
> >> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> >> index 2de6b41..5edba06 100644
> >> --- a/drivers/gpu/drm/i915/intel_drv.h
> >> +++ b/drivers/gpu/drm/i915/intel_drv.h
> >> @@ -2047,6 +2047,8 @@ void lspcon_set_infoframes(struct drm_encoder *encoder,
> >> const struct drm_connector_state *conn_state);
> >> bool lspcon_infoframe_enabled(struct drm_encoder *encoder,
> >> const struct intel_crtc_state *pipe_config);
> >> +bool lspcon_ycbcr420_config(struct drm_connector *connector,
> >> + struct intel_crtc_state *config);
> >>
> >> /* intel_pipe_crc.c */
> >> int intel_pipe_crc_create(struct drm_minor *minor);
> >> diff --git a/drivers/gpu/drm/i915/intel_lspcon.c b/drivers/gpu/drm/i915/intel_lspcon.c
> >> index 066ea91..cb88138 100644
> >> --- a/drivers/gpu/drm/i915/intel_lspcon.c
> >> +++ b/drivers/gpu/drm/i915/intel_lspcon.c
> >> @@ -180,6 +180,25 @@ static bool lspcon_wake_native_aux_ch(struct intel_lspcon *lspcon)
> >> return true;
> >> }
> >>
> >> +bool lspcon_ycbcr420_config(struct drm_connector *connector,
> >> + struct intel_crtc_state *config)
> >> +{
> >> + struct drm_display_info *info = &connector->display_info;
> >> + struct drm_display_mode *mode = &config->base.adjusted_mode;
> >> +
> >> + if (drm_mode_is_420_only(info, mode)) {
> >> + if (!connector->ycbcr_420_allowed) {
> >> + DRM_ERROR("Platform doesn't support YCBCR420 output\n");
> >> + return false;
> >> + }
> >> +
> >> + config->port_clock /= 2;
> >> + return true;
> >> + }
> >> +
> >> + return false;
> >> +}
> >> +
> >> static bool lspcon_probe(struct intel_lspcon *lspcon)
> >> {
> >> int retry;
> >> @@ -459,6 +478,13 @@ void lspcon_set_infoframes(struct drm_encoder *encoder,
> >> return;
> >> }
> >>
> >> + if (lspcon->output_format == CRTC_OUTPUT_YCBCR420)
> >> + frame.avi.colorspace = HDMI_COLORSPACE_YUV420;
> >> + else if (lspcon->output_format == CRTC_OUTPUT_YCBCR444)
> >> + frame.avi.colorspace = HDMI_COLORSPACE_YUV444;
> >> + else
> >> + frame.avi.colorspace = HDMI_COLORSPACE_RGB;
> >> +
> >> drm_hdmi_avi_infoframe_quant_range(&frame.avi, mode,
> >> crtc_state->limited_color_range ?
> >> HDMI_QUANTIZATION_RANGE_LIMITED :
> >> @@ -512,6 +538,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
> >> struct intel_lspcon *lspcon = &intel_dig_port->lspcon;
> >> struct drm_device *dev = intel_dig_port->base.base.dev;
> >> struct drm_i915_private *dev_priv = to_i915(dev);
> >> + struct drm_connector *connector = &dp->attached_connector->base;
> >>
> >> if (!HAS_LSPCON(dev_priv)) {
> >> DRM_ERROR("LSPCON is not supported on this platform\n");
> >> @@ -536,6 +563,7 @@ bool lspcon_init(struct intel_digital_port *intel_dig_port)
> >> return false;
> >> }
> >>
> >> + connector->ycbcr_420_allowed = true;
> >> lspcon->active = true;
> >> DRM_DEBUG_KMS("Success: LSPCON init\n");
> >> return true;
> >> --
> >> 2.7.4

--
Ville Syrjälä
Intel OTC