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However, display driver > > typically determines the maximum available bpc based on HW bandwidth. > > > > This patch introduces a new debugfs that allow user to configure > > dedicated bpc manually, and making HDMI compliance test much easier. > > There is already the intel_force_link_bpp connector debugfs entry, IMO > that should be enabled for all HDMI connectors (atm it's used only for > those that are on an FDI link), instead of adding a new debugfs entry. There is also the "max bpc" connector property. If that doesn't work in your usecase could you explain why? > > Cc: Shankar Uma > > Signed-off-by: Lee Shawn C > > --- > > .../drm/i915/display/intel_display_debugfs.c | 58 +++++++++++++++++++ > > .../drm/i915/display/intel_display_types.h | 2 + > > drivers/gpu/drm/i915/display/intel_hdmi.c | 7 +++ > > 3 files changed, 67 insertions(+) > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c > > index ce3f9810c42d..cca115a6f130 100644 > > --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c > > +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c > > @@ -1208,6 +1208,56 @@ static const struct file_operations i915_dsc_fractional_bpp_fops = { > > .write = i915_dsc_fractional_bpp_write > > }; > > > > +static int i915_hdmi_req_bpc_show(struct seq_file *m, void *data) > > +{ > > + struct intel_connector *connector = m->private; > > + > > + seq_printf(m, "request bpc: %u\n", connector->force_hdmi_bpc); > > + > > + return 0; > > +} > > + > > +static ssize_t i915_hdmi_req_bpc_write(struct file *file, > > + const char __user *ubuf, > > + size_t len, loff_t *offp) > > +{ > > + struct seq_file *m = file->private_data; > > + struct intel_connector *intel_connector = m->private; > > + struct intel_display *display = to_intel_display(intel_connector); > > + int new_bpc = 0, ret = 0; > > + char *kbuf; > > + const char *p; > > + > > + kbuf = memdup_user_nul(ubuf, len); > > + if (IS_ERR(kbuf)) > > + return PTR_ERR(kbuf); > > + > > + p = strim(kbuf); > > + > > + ret = kstrtoint(p, 0, &new_bpc); > > + if (ret < 0) > > + return -EINVAL; > > + > > + switch (new_bpc) { > > + case 0: > > + case 8: > > + case 10: > > + case 12: > > + break; > > + default: > > + drm_dbg(display->drm, > > + "HDMI bpc (%u) may exceed the max value (12)\n", new_bpc); > > + return -EINVAL; > > + } > > + > > + intel_connector->force_hdmi_bpc = new_bpc; > > + > > + *offp += len; > > + kfree(kbuf); > > + return len; > > +} > > +DEFINE_SHOW_STORE_ATTRIBUTE(i915_hdmi_req_bpc); > > + > > /* > > * Returns the Current CRTC's bpc. > > * Example usage: cat /sys/kernel/debug/dri/0/crtc-0/i915_current_bpc > > @@ -1359,6 +1409,13 @@ void intel_connector_debugfs_add(struct intel_connector *connector) > > connector_type == DRM_MODE_CONNECTOR_HDMIB) > > debugfs_create_file("i915_lpsp_capability", 0444, root, > > connector, &i915_lpsp_capability_fops); > > + > > + if (connector_type == DRM_MODE_CONNECTOR_HDMIA || > > + connector_type == DRM_MODE_CONNECTOR_HDMIB) { > > + connector->force_hdmi_bpc = 0; > > + debugfs_create_file("i915_force_hdmi_bpc", 0644, root, > > + connector, &i915_hdmi_req_bpc_fops); > > + } > > } > > > > /** > > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h > > index 4d9df803ad47..e1e42d701f68 100644 > > --- a/drivers/gpu/drm/i915/display/intel_display_types.h > > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h > > @@ -564,6 +564,8 @@ struct intel_connector { > > struct work_struct modeset_retry_work; > > > > struct intel_hdcp hdcp; > > + > > + u8 force_hdmi_bpc; > > }; > > > > struct intel_digital_connector_state { > > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c > > index cbee628eb26b..0aa4044e2854 100644 > > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c > > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c > > @@ -2118,6 +2118,7 @@ static int intel_hdmi_compute_bpc(struct intel_encoder *encoder, > > int clock, bool respect_downstream_limits) > > { > > struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(encoder); > > + struct intel_connector *intel_connector = intel_hdmi->attached_connector; > > int bpc; > > > > /* > > @@ -2134,6 +2135,12 @@ static int intel_hdmi_compute_bpc(struct intel_encoder *encoder, > > if (!respect_downstream_limits) > > bpc = 8; > > > > + /* > > + * overwrite bpc per user's request > > + */ > > + if (intel_connector->force_hdmi_bpc) > > + bpc = intel_connector->force_hdmi_bpc; > > + > > for (; bpc >= 8; bpc -= 2) { > > int tmds_clock = intel_hdmi_tmds_clock(clock, bpc, > > crtc_state->sink_format); > > -- > > 2.34.1 > >