[PATCH 0/1] drm/vc4: hdmi: Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi

[PATCH 0/1] drm/vc4: hdmi: Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi

[José Expósito]

Hello everyone,

This patch replaces the calls to drm_detect_hdmi_monitor() with the more
efficient drm_display_info.is_hdmi in the VC4 driver.

After applying it, vc4_encoder->hdmi_monitor could be removed in a
follow up patch. However, since it is used by some code not present in
the mainline kernel but present in the Raspberry Pi tree [1] I decided
to send only this first patch and see if the maintainers also want to
remove vc4_encoder->hdmi_monitor.

Best wishes,
José Expósito

[1] https://github.com/raspberrypi/linux/blob/rpi-5.15.y/drivers/gpu/drm/vc4/vc4_firmware_kms.c#L1410

José Expósito (1):
  drm/vc4: hdmi: Replace drm_detect_hdmi_monitor() with is_hdmi

 drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.25.1

[PATCH 1/1] drm/vc4: hdmi: Replace drm_detect_hdmi_monitor() with is_hdmi

[José Expósito]

Once EDID is parsed, the monitor HDMI support information is cached in
drm_display_info.is_hdmi by drm_parse_hdmi_vsdb_video().

This driver calls drm_detect_hdmi_monitor() to receive the same
information and stores its own cached value, which is less efficient.

Avoid calling drm_detect_hdmi_monitor() and use drm_display_info.is_hdmi
instead.

drm_detect_hdmi_monitor() is called in vc4_hdmi_connector_detect() and
vc4_hdmi_connector_get_modes(). In both cases it is safe to rely on
drm_display_info.is_hdmi as shown by ftrace:

vc4_hdmi_connector_detect:

    vc4_hdmi_connector_detect() {
      drm_get_edid() {
        drm_connector_update_edid_property() {
          drm_add_display_info() {
            drm_reset_display_info();
            drm_for_each_detailed_block.part.0();
            drm_parse_cea_ext() {
              drm_find_cea_extension();
              cea_db_offsets.part.0();
              cea_db_is_hdmi_vsdb.part.0();
              drm_parse_hdmi_vsdb_video();
              /* drm_display_info.is_hdmi is cached here */
            }
          }
        }
      }
      /* drm_display_info.is_hdmi is used here */
    }

vc4_hdmi_connector_get_modes:

    vc4_hdmi_connector_get_modes() {
      drm_get_edid() {
        drm_connector_update_edid_property() {
          drm_add_display_info() {
            drm_reset_display_info();
            drm_for_each_detailed_block.part.0();
            drm_parse_cea_ext() {
              drm_find_cea_extension();
              cea_db_offsets.part.0();
              cea_db_is_hdmi_vsdb.part.0();
              drm_parse_hdmi_vsdb_video();
              /* drm_display_info.is_hdmi is cached here */
            }
          }
        }
      }
      /* drm_display_info.is_hdmi is used here */
      drm_connector_update_edid_property();
    }

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 6c58b0fd13fb..ecdb1ffc2023 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -216,7 +216,7 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
 
 			if (edid) {
 				cec_s_phys_addr_from_edid(vc4_hdmi->cec_adap, edid);
-				vc4_hdmi->encoder.hdmi_monitor = drm_detect_hdmi_monitor(edid);
+				vc4_hdmi->encoder.hdmi_monitor = connector->display_info.is_hdmi;
 				kfree(edid);
 			}
 		}
@@ -255,7 +255,7 @@ static int vc4_hdmi_connector_get_modes(struct drm_connector *connector)
 		goto out;
 	}
 
-	vc4_encoder->hdmi_monitor = drm_detect_hdmi_monitor(edid);
+	vc4_encoder->hdmi_monitor = connector->display_info.is_hdmi;
 
 	drm_connector_update_edid_property(connector, edid);
 	ret = drm_add_edid_modes(connector, edid);
-- 
2.25.1

Re: [PATCH 1/1] drm/vc4: hdmi: Replace drm_detect_hdmi_monitor() with is_hdmi

[Maxime Ripard]

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Hi Jose,

On Wed, Apr 06, 2022 at 06:55:14PM +0200, José Expósito wrote:
> Once EDID is parsed, the monitor HDMI support information is cached in
> drm_display_info.is_hdmi by drm_parse_hdmi_vsdb_video().
> 
> This driver calls drm_detect_hdmi_monitor() to receive the same
> information and stores its own cached value, which is less efficient.
> 
> Avoid calling drm_detect_hdmi_monitor() and use drm_display_info.is_hdmi
> instead.
> 
> drm_detect_hdmi_monitor() is called in vc4_hdmi_connector_detect() and
> vc4_hdmi_connector_get_modes(). In both cases it is safe to rely on
> drm_display_info.is_hdmi as shown by ftrace:

How do you use ftrace to generate that?

> vc4_hdmi_connector_detect:
> 
>     vc4_hdmi_connector_detect() {
>       drm_get_edid() {
>         drm_connector_update_edid_property() {
>           drm_add_display_info() {
>             drm_reset_display_info();
>             drm_for_each_detailed_block.part.0();
>             drm_parse_cea_ext() {
>               drm_find_cea_extension();
>               cea_db_offsets.part.0();
>               cea_db_is_hdmi_vsdb.part.0();
>               drm_parse_hdmi_vsdb_video();
>               /* drm_display_info.is_hdmi is cached here */
>             }
>           }
>         }
>       }
>       /* drm_display_info.is_hdmi is used here */
>     }
> 
> vc4_hdmi_connector_get_modes:
> 
>     vc4_hdmi_connector_get_modes() {
>       drm_get_edid() {
>         drm_connector_update_edid_property() {
>           drm_add_display_info() {
>             drm_reset_display_info();
>             drm_for_each_detailed_block.part.0();
>             drm_parse_cea_ext() {
>               drm_find_cea_extension();
>               cea_db_offsets.part.0();
>               cea_db_is_hdmi_vsdb.part.0();
>               drm_parse_hdmi_vsdb_video();
>               /* drm_display_info.is_hdmi is cached here */
>             }
>           }
>         }
>       }
>       /* drm_display_info.is_hdmi is used here */
>       drm_connector_update_edid_property();
>     }
> 
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>

I think what you're hinting at in the cover letter would be best though:
we should just remove that caching entirely and use is_hdmi everywhere

Maxime

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Re: [PATCH 1/1] drm/vc4: hdmi: Replace drm_detect_hdmi_monitor() with is_hdmi

[José Expósito]

Hi Maxime,

Thanks for your comments.

On Fri, Apr 08, 2022 at 09:41:10AM +0200, Maxime Ripard wrote:
> Hi Jose,
> 
> On Wed, Apr 06, 2022 at 06:55:14PM +0200, José Expósito wrote:
> > Once EDID is parsed, the monitor HDMI support information is cached in
> > drm_display_info.is_hdmi by drm_parse_hdmi_vsdb_video().
> > 
> > This driver calls drm_detect_hdmi_monitor() to receive the same
> > information and stores its own cached value, which is less efficient.
> > 
> > Avoid calling drm_detect_hdmi_monitor() and use drm_display_info.is_hdmi
> > instead.
> > 
> > drm_detect_hdmi_monitor() is called in vc4_hdmi_connector_detect() and
> > vc4_hdmi_connector_get_modes(). In both cases it is safe to rely on
> > drm_display_info.is_hdmi as shown by ftrace:
> 
> How do you use ftrace to generate that?

I had to add noinline to a couple of relevant functions and run the
usual:

$ sudo trace-cmd record -p function_graph -l "vc4_hdmi_*" [...]

I'll add the command to v2.

 
> > vc4_hdmi_connector_detect:
> > 
> >     vc4_hdmi_connector_detect() {
> >       drm_get_edid() {
> >         drm_connector_update_edid_property() {
> >           drm_add_display_info() {
> >             drm_reset_display_info();
> >             drm_for_each_detailed_block.part.0();
> >             drm_parse_cea_ext() {
> >               drm_find_cea_extension();
> >               cea_db_offsets.part.0();
> >               cea_db_is_hdmi_vsdb.part.0();
> >               drm_parse_hdmi_vsdb_video();
> >               /* drm_display_info.is_hdmi is cached here */
> >             }
> >           }
> >         }
> >       }
> >       /* drm_display_info.is_hdmi is used here */
> >     }
> > 
> > vc4_hdmi_connector_get_modes:
> > 
> >     vc4_hdmi_connector_get_modes() {
> >       drm_get_edid() {
> >         drm_connector_update_edid_property() {
> >           drm_add_display_info() {
> >             drm_reset_display_info();
> >             drm_for_each_detailed_block.part.0();
> >             drm_parse_cea_ext() {
> >               drm_find_cea_extension();
> >               cea_db_offsets.part.0();
> >               cea_db_is_hdmi_vsdb.part.0();
> >               drm_parse_hdmi_vsdb_video();
> >               /* drm_display_info.is_hdmi is cached here */
> >             }
> >           }
> >         }
> >       }
> >       /* drm_display_info.is_hdmi is used here */
> >       drm_connector_update_edid_property();
> >     }
> > 
> > Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> 
> I think what you're hinting at in the cover letter would be best though:
> we should just remove that caching entirely and use is_hdmi everywhere

Cool, I'll work on a follow up patch to remove vc4_encoder.hdmi_monitor
and add it to v2.

Thanks,
Jose