Re: [PATCH v9 20/24] drm/i915/dsc: Add Per connector debugfs node for DSC support/enable

[Manasi Navare <manasi.d.navare@intel.com>]

On Mon, Nov 19, 2018 at 10:27:44PM +0200, Ville Syrjälä wrote:
> On Thu, Nov 15, 2018 at 05:39:42PM -0800, Manasi Navare wrote:
> > On Tue, Nov 13, 2018 at 05:52:28PM -0800, Manasi Navare wrote:
> > > DSC can be supported per DP connector. This patch adds a per connector
> > > debugfs node to expose DSC support capability by the kernel.
> > > The same node can be used from userspace to force DSC enable.
> > > 
> > > force_dsc_en written through this debugfs node is used to force
> > > DSC even for lower resolutions.
> > > 
> > > v4:
> > > * Add missed connector_status check (Manasi)
> > > * Create i915_dsc_support node only for Gen >=10 (manasi)
> > > * Access intel_dp->dsc_dpcd only if its not NULL (Manasi)
> > > v3:
> > > * Combine Force_dsc_en with this patch (Ville)
> > > v2:
> > > * Use kstrtobool_from_user to avoid explicit error checking (Lyude)
> > > * Rebase on drm-tip (Manasi)
> > > 
> > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > > Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
> > > Cc: Lyude Paul <lyude@redhat.com>
> > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > > Reviewed-by: Lyude Paul <lyude@redhat.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_debugfs.c | 77 +++++++++++++++++++++++++++++
> > >  drivers/gpu/drm/i915/intel_dp.c     |  3 +-
> > >  drivers/gpu/drm/i915/intel_drv.h    |  3 ++
> > >  3 files changed, 82 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > > index 670db5073d70..3c112bb225d6 100644
> > > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > > @@ -5074,6 +5074,76 @@ static int i915_hdcp_sink_capability_show(struct seq_file *m, void *data)
> > >  }
> > >  DEFINE_SHOW_ATTRIBUTE(i915_hdcp_sink_capability);
> > >  
> > > +static int i915_dsc_support_show(struct seq_file *m, void *data)
> > > +{
> > > +	struct drm_connector *connector = m->private;
> > > +	struct intel_encoder *encoder = intel_attached_encoder(connector);
> > > +	struct intel_dp *intel_dp =
> > > +		enc_to_intel_dp(&encoder->base);
> > > +	struct intel_crtc *crtc;
> > > +	struct intel_crtc_state *crtc_state;
> > > +
> > > +	if (connector->status != connector_status_connected)
> > > +		return -ENODEV;
> > > +
> > > +	crtc = to_intel_crtc(encoder->base.crtc);
> > > +	crtc_state = to_intel_crtc_state(crtc->base.state);
> 
> This stuff is broken. If you want to root around in the atomic states
> you need to grab some locks first.

I thought using the drm_modeset_lock before grabbing the crtc_state value should
be enough.

Are you referring to using the locks like:
drm_modeset_lock_single_interruptible()?

> 
> > > +	drm_modeset_lock(&crtc->base.mutex, NULL);
> > > +	seq_printf(m, "Enabled: %s\n",
> > > +		   yesno(crtc_state->dsc_params.compression_enable));
> > > +	if (intel_dp->dsc_dpcd)
> > > +		seq_printf(m, "Supported: %s\n",
> > > +			   yesno(drm_dp_sink_supports_dsc(intel_dp->dsc_dpcd)));
> > 
> > I think this supported should also use the intel_dp_supports_dsc() helper so
> > it checks for sink support and platform support as well.
> > 
> > Ville, what do you think?
> 
> Possibly. We may want to report per-crtc whether DSC is possible or not
> (due to transcoder A not being capable of DSC). And to do that we
> actually need to change intel_dp_source_supports_dsc() & co. to not take
> the crtc state, and rather we just need to pass in the transcoder. That
> would mean we have to determine the correct transcoder here. Perhaps
> a better alternative would be to pass in pipe/crtc + port and let the
> function derive the transcoder itself. That would keep the
> pipe+port->transcoder logic in one place. Actually we have that logic
> in two places at least already (intel_ddi_compute_config() and
> intel_ddi_connector_get_hw_state()). We could extract that bit into
> a small helper that gets called by all three places.

So there would be Sink_Supported and Enabled separately and then for 
for_each_crtc loop and report out Source_supported for every crtc
by passing port and pipe/crtc and determining transcoder from that find
the intel_dp_source_supports_dsc for that transcoder ?

Is this the correct way?
Also should this be kept separately in a follow on series and get the simpler
version of intel_dp_supports_dsc() merged first?

Manasi

> 
> > 
> > Manasi
> > 
> > > +	drm_modeset_unlock(&crtc->base.mutex);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static ssize_t i915_dsc_support_write(struct file *file,
> > > +				      const char __user *ubuf,
> > > +				      size_t len, loff_t *offp)
> > > +{
> > > +	bool dsc_enable = false;
> > > +	int ret;
> > > +	struct drm_connector *connector =
> > > +		((struct seq_file *)file->private_data)->private;
> > > +	struct intel_encoder *encoder = intel_attached_encoder(connector);
> > > +	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> > > +
> > > +	if (len == 0)
> > > +		return 0;
> > > +
> > > +	DRM_DEBUG_DRIVER("Copied %d bytes from user to force DSC\n",
> > > +			 (unsigned int)len);
> > > +
> > > +	ret = kstrtobool_from_user(ubuf, len, &dsc_enable);
> > > +	if (ret < 0)
> > > +		return ret;
> > > +
> > > +	DRM_DEBUG_DRIVER("Got %s for DSC Enable\n",
> > > +			 (dsc_enable) ? "true" : "false");
> > > +	intel_dp->force_dsc_en = dsc_enable;
> > > +
> > > +	*offp += len;
> > > +	return len;
> > > +}
> > > +
> > > +static int i915_dsc_support_open(struct inode *inode,
> > > +				 struct file *file)
> > > +{
> > > +	return single_open(file, i915_dsc_support_show,
> > > +			   inode->i_private);
> > > +}
> > > +
> > > +static const struct file_operations i915_dsc_support_fops = {
> > > +	.owner = THIS_MODULE,
> > > +	.open = i915_dsc_support_open,
> > > +	.read = seq_read,
> > > +	.llseek = seq_lseek,
> > > +	.release = single_release,
> > > +	.write = i915_dsc_support_write
> > > +};
> > > +
> > >  /**
> > >   * i915_debugfs_connector_add - add i915 specific connector debugfs files
> > >   * @connector: pointer to a registered drm_connector
> > > @@ -5086,6 +5156,7 @@ DEFINE_SHOW_ATTRIBUTE(i915_hdcp_sink_capability);
> > >  int i915_debugfs_connector_add(struct drm_connector *connector)
> > >  {
> > >  	struct dentry *root = connector->debugfs_entry;
> > > +	struct drm_i915_private *dev_priv = to_i915(connector->dev);
> > >  
> > >  	/* The connector must have been registered beforehands. */
> > >  	if (!root)
> > > @@ -5110,5 +5181,11 @@ int i915_debugfs_connector_add(struct drm_connector *connector)
> > >  				    connector, &i915_hdcp_sink_capability_fops);
> > >  	}
> > >  
> > > +	if (INTEL_GEN(dev_priv) >= 10 &&
> > > +	    (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
> > > +	     connector->connector_type == DRM_MODE_CONNECTOR_eDP))
> > > +		debugfs_create_file("i915_dsc_support", S_IRUGO, root,
> > > +				    connector, &i915_dsc_support_fops);
> > > +
> > >  	return 0;
> > >  }
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > > index b43a77bf42df..99e0dd0e32d6 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -2042,7 +2042,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
> > >  							&limits);
> > >  
> > >  	/* enable compression if the mode doesn't fit available BW */
> > > -	if (!ret) {
> > > +	if (!ret || intel_dp->force_dsc_en) {
> > >  		if (!intel_dp_dsc_compute_config(intel_dp, pipe_config,
> > >  						 conn_state, &limits))
> > >  			return false;
> > > @@ -2135,6 +2135,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> > >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> > >  		return false;
> > >  
> > > +	DRM_DEBUG_KMS("Force DSC en = %d\n", intel_dp->force_dsc_en);
> > >  	if (!intel_dp_compute_link_config(encoder, pipe_config, conn_state))
> > >  		return false;
> > >  
> > > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > > index 92e987fc3d9f..9eeb08142327 100644
> > > --- a/drivers/gpu/drm/i915/intel_drv.h
> > > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > > @@ -1200,6 +1200,9 @@ struct intel_dp {
> > >  
> > >  	/* Displayport compliance testing */
> > >  	struct intel_dp_compliance compliance;
> > > +
> > > +	/* Display stream compression testing */
> > > +	bool force_dsc_en;
> > >  };
> > >  
> > >  enum lspcon_vendor {
> > > -- 
> > > 2.19.1
> > > 
> 
> -- 
> Ville Syrjälä
> Intel
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