Re: [PATCH 2/3] drm/i915: Reinitialize sink scrambling/TMDS clock ratio on HPD

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Jan 22, 2018 at 12:07:28PM +0530, Sharma, Shashank wrote:
> Regards
> 
> Shashank
> 
> 
> On 1/13/2018 2:34 AM, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > The LG 4k TV I have doesn't deassert HPD when I turn the TV off, but
> > when I turn it back on it will pulse the HPD line. By that time it has
> > forgotten everything we told it about scrambling and the clock ratio.
> > Hence if we want to get a picture out if it again we have to tell it
> > whether we're currently sending scrambled data or not. Implement
> > that via the encoder->hotplug() hook.
> >
> > v2: Force a full modeset to not follow the HDMI 2.0 spec more
> >      closely (Shashank)
> >
> > Cc: Shashank Sharma <shashank.sharma@intel.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/intel_ddi.c | 146 ++++++++++++++++++++++++++++++++++++++-
> >   1 file changed, 145 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index 1aeae3e97013..25793bdc692f 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -25,6 +25,7 @@
> >    *
> >    */
> >   
> > +#include <drm/drm_scdc_helper.h>
> >   #include "i915_drv.h"
> >   #include "intel_drv.h"
> >   
> > @@ -2756,6 +2757,146 @@ intel_ddi_init_dp_connector(struct intel_digital_port *intel_dig_port)
> >   	return connector;
> >   }
> >   
> > +static int modeset_pipe(struct drm_crtc *crtc,
> > +			struct drm_modeset_acquire_ctx *ctx)
> Should this function go to intel_atomic.c or similar ?

Do you have another user for it? If not I don't see a particularly
good reason for moving it out.

> Also a little 
> documentation about
> usage will be helpful for others, who want to reuse this.

What should it say? To me the function name is pretty clear.

> > +{
> > +	struct drm_atomic_state *state;
> > +	struct drm_crtc_state *crtc_state;
> > +	int ret;
> > +
> > +	state = drm_atomic_state_alloc(crtc->dev);
> > +	if (!state)
> > +		return -ENOMEM;
> > +
> > +	state->acquire_ctx = ctx;
> > +
> > +	crtc_state = drm_atomic_get_crtc_state(state, crtc);
> > +	if (IS_ERR(crtc_state)) {
> > +		ret = PTR_ERR(crtc_state);
> > +		goto out;
> > +	}
> > +
> > +	crtc_state->mode_changed = true;
> > +
> > +	ret = drm_atomic_add_affected_connectors(state, crtc);
> > +	if (ret)
> > +		goto out;
> > +
> > +	ret = drm_atomic_add_affected_planes(state, crtc);
> > +	if (ret)
> > +		goto out;
> > +
> > +	ret = drm_atomic_commit(state);
> > +	if (ret)
> > +		goto out;
> > +
> As this is an internal modeset trigger, should we send an event to 
> userspace about this ?

What would userspace do with such an event?

> > +	return 0;
> > +
> > + out:
> one debug message here telling us about if modeset was success/fail ?

There's a WARN already higher up.

> > +	drm_atomic_state_put(state);
> > +
> > +	return ret;
> > +}
> > +
> > +static int intel_hdmi_reset_link(struct intel_encoder *encoder,
> > +				 struct drm_modeset_acquire_ctx *ctx)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> > +	struct intel_hdmi *hdmi = enc_to_intel_hdmi(&encoder->base);
> > +	struct intel_connector *connector = hdmi->attached_connector;
> > +	struct i2c_adapter *adapter =
> > +		intel_gmbus_get_adapter(dev_priv, hdmi->ddc_bus);
> > +	struct drm_connector_state *conn_state;
> > +	struct intel_crtc_state *crtc_state;
> > +	struct intel_crtc *crtc;
> > +	u8 config;
> > +	int ret;
> > +
> > +	if (!connector || connector->base.status != connector_status_connected)
> > +		return 0;
> > +
> > +	ret = drm_modeset_lock(&dev_priv->drm.mode_config.connection_mutex, ctx);
> > +	if (ret)
> > +		return ret;
> > +
> > +	conn_state = connector->base.state;
> > +
> > +	crtc = to_intel_crtc(conn_state->crtc);
> > +	if (!crtc)
> > +		return 0;
> > +
> > +	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
> > +	if (ret)
> > +		return ret;
> > +
> > +	crtc_state = to_intel_crtc_state(crtc->base.state);
> > +
> > +	WARN_ON(!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI));
> > +
> > +	if (!crtc_state->base.active)
> > +		return 0;
> > +
> > +	if (!crtc_state->hdmi_high_tmds_clock_ratio &&
> > +	    !crtc_state->hdmi_scrambling)
> > +		return 0;
> > +
> > +	if (conn_state->commit &&
> > +	    !try_wait_for_completion(&conn_state->commit->hw_done))
> > +		return 0;
> > +
> > +	ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
> > +	if (ret < 0) {
> > +		DRM_ERROR("Failed to read TMDS config: %d\n", ret);
> > +		return 0;
> > +	}
> We can export this read as helper in scdc_helper.c, something like 
> drm_scdc_get_tmds_clock_ratio ?

Feels like fairly pointless abstraction to me. And we'd either need
to do two SCDC reads instead of one, or return two things from said
function.

> - Shashank
> > +
> > +	if (!!(config & SCDC_TMDS_BIT_CLOCK_RATIO_BY_40) ==
> > +	    crtc_state->hdmi_high_tmds_clock_ratio &&
> > +	    !!(config & SCDC_SCRAMBLING_ENABLE) ==
> > +	    crtc_state->hdmi_scrambling)
> > +		return 0;
> > +
> > +	/*
> > +	 * HDMI 2.0 says that one should not send scrambled data
> > +	 * prior to configuring the sink scrambling, and that
> > +	 * TMDS clock/data transmission should be suspended when
> > +	 * changing the TMDS clock rate in the sink. So let's
> > +	 * just do a full modeset here, even though some sinks
> > +	 * would be perfectly happy if were to just reconfigure
> > +	 * the SCDC settings on the fly.
> > +	 */
> > +	return modeset_pipe(&crtc->base, ctx);
> > +}
> > +
> > +static bool intel_ddi_hotplug(struct intel_encoder *encoder,
> > +			      struct intel_connector *connector)
> > +{
> > +	struct drm_modeset_acquire_ctx ctx;
> > +	bool changed;
> > +	int ret;
> > +
> > +	changed = intel_encoder_hotplug(encoder, connector);
> > +
> > +	drm_modeset_acquire_init(&ctx, 0);
> > +
> > +	for (;;) {
> > +		ret = intel_hdmi_reset_link(encoder, &ctx);
> > +
> > +		if (ret == -EDEADLK) {
> > +			drm_modeset_backoff(&ctx);
> > +			continue;
> > +		}
> > +
> > +		break;
> > +	}
> > +
> > +	drm_modeset_drop_locks(&ctx);
> > +	drm_modeset_acquire_fini(&ctx);
> > +	WARN(ret, "Acquiring modeset locks failed with %i\n", ret);
> > +
> > +	return changed;
> > +}
> > +
> >   static struct intel_connector *
> >   intel_ddi_init_hdmi_connector(struct intel_digital_port *intel_dig_port)
> >   {
> > @@ -2866,7 +3007,10 @@ void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
> >   	drm_encoder_init(&dev_priv->drm, encoder, &intel_ddi_funcs,
> >   			 DRM_MODE_ENCODER_TMDS, "DDI %c", port_name(port));
> >   
> > -	intel_encoder->hotplug = intel_encoder_hotplug;
> > +	if (init_hdmi)
> > +		intel_encoder->hotplug = intel_ddi_hotplug;
> > +	else
> > +		intel_encoder->hotplug = intel_encoder_hotplug;
> >   	intel_encoder->compute_output_type = intel_ddi_compute_output_type;
> >   	intel_encoder->compute_config = intel_ddi_compute_config;
> >   	intel_encoder->enable = intel_enable_ddi;

-- 
Ville Syrjälä
Intel OTC
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