On Thu, Oct 24, 2019 at 05:20:32PM +0300, Ville Syrjälä wrote:
> On Thu, Oct 24, 2019 at 03:54:41PM +0200, Thierry Reding wrote:
> > On Thu, Oct 24, 2019 at 02:34:00PM +0300, Ville Syrjälä wrote:
> > > On Thu, Oct 24, 2019 at 12:31:06PM +0200, Thierry Reding wrote:
> > > > On Wed, Oct 23, 2019 at 05:00:41PM -0700, Manasi Navare wrote:
> > > > > Adaptive Sync is a VESA feature so add a DRM core helper to parse
> > > > > the EDID's detailed descritors to obtain the adaptive sync monitor range.
> > > > > Store this info as part fo drm_display_info so it can be used
> > > > > across all drivers.
> > > > > This part of the code is stripped out of amdgpu's function
> > > > > amdgpu_dm_update_freesync_caps() to make it generic and be used
> > > > > across all DRM drivers
> > > > >
> > > > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > > > > Cc: Harry Wentland <harry.wentland@xxxxxxx>
> > > > > Cc: Clinton A Taylor <clinton.a.taylor@xxxxxxxxx>
> > > > > Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> > > > > ---
> > > > > drivers/gpu/drm/drm_edid.c | 49 +++++++++++++++++++++++++++++++++++++
> > > > > include/drm/drm_connector.h | 25 +++++++++++++++++++
> > > > > include/drm/drm_edid.h | 2 ++
> > > > > 3 files changed, 76 insertions(+)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > > > > index 474ac04d5600..97dd1200773e 100644
> > > > > --- a/drivers/gpu/drm/drm_edid.c
> > > > > +++ b/drivers/gpu/drm/drm_edid.c
> > > > > @@ -4707,6 +4707,52 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
> > > > > }
> > > > > }
> > > > >
> > > > > +void drm_get_adaptive_sync_limits(struct drm_connector *connector,
> > > > > + const struct edid *edid)
> > > > > +{
> > > > > + struct drm_display_info *info = &connector->display_info;
> > > > > + const struct detailed_timing *timing;
> > > > > + const struct detailed_non_pixel *data;
> > > > > + const struct detailed_data_monitor_range *range;
> > > > > + int i;
> > > >
> > > > This can be unsigned int.
> > >
> > > Please no. A loop iterator called 'i' should always be a normal signed int.
> >
> > What? Where's that rule written down? In my experience it's always
> > better to use as restrictive a type as possible. It's really annoying
> > when GCC suddenly starts complaining about comparison between signed and
> > unsigned. So if a variable can never contain a signed value, why risk
> > the ambiguity? The value goes from 0 to 4, the sign bit is useless.
>
> Dunno if it's really written down anywhere. It's just something
> experience has taught. IIRC there's also a rant from Linus about this
> somewhere. Hm, can't find that one right now, but Andrew Morton also
> seems to agree: https://lwn.net/Articles/309279/
> Ah, here is one Linus rant about unsigned array indexes:
> https://yarchive.net/comp/linux/gcc.html
>
> My opinion: unsigned is an very *dangerous* keyword in C that demands
> your respect. You should never use it without thinking first what the
> ramifications are. You always have to have the promotion rules clear
> in you mind when you do any kind of arithmetic with >= unsigned int
> type. And common idioms such as 'int i' should be respected so as to
> not cause unexpected hair loss to other developers when they decide
> to make the loop iterate backwards.
>
> >
> > > > > + /*
> > > > > + * Restrict Adaptive Sync only for dp and edp
> > > > > + */
> > > > > + if (connector->connector_type != DRM_MODE_CONNECTOR_DisplayPort &&
> > > > > + connector->connector_type != DRM_MODE_CONNECTOR_eDP)
> > > > > + return;
> > > > > +
> > > > > + if (edid->version <= 1 && !(edid->version == 1 && edid->revision > 1))
> > > > > + return;
> > > > > +
> > > > > + for (i = 0; i < 4; i++) {
> > > > > + timing = &edid->detailed_timings[i];
> > > > > + data = &timing->data.other_data;
> > > > > + range = &data->data.range;
> > > > > + /*
> > > > > + * Check if monitor has continuous frequency mode
> > > > > + */
> > > > > + if (data->type != EDID_DETAIL_MONITOR_RANGE)
> > > > > + continue;
> > > > > + /*
> > > > > + * Check for flag range limits only. If flag == 1 then
> > > > > + * no additional timing information provided.
> > > > > + * Default GTF, GTF Secondary curve and CVT are not
> > > > > + * supported
> > > > > + */
> > > > > + if (range->flags != 1)
> > > > > + continue;
> > > > > +
> > > > > + info->adaptive_sync.min_vfreq = range->min_vfreq;
> > > > > + info->adaptive_sync.max_vfreq = range->max_vfreq;
> > > > > + info->adaptive_sync.pixel_clock_mhz =
> > > > > + range->pixel_clock_mhz * 10;
> > > > > + break;
> > > > > + }
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_get_adaptive_sync_limits);
> > > > > +
> > > > > /* A connector has no EDID information, so we've got no EDID to compute quirks from. Reset
> > > > > * all of the values which would have been set from EDID
> > > > > */
> > > > > @@ -4728,6 +4774,7 @@ drm_reset_display_info(struct drm_connector *connector)
> > > > > memset(&info->hdmi, 0, sizeof(info->hdmi));
> > > > >
> > > > > info->non_desktop = 0;
> > > > > + memset(&info->adaptive_sync, 0, sizeof(info->adaptive_sync));
> > > > > }
> > > > >
> > > > > u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edid)
> > > > > @@ -4743,6 +4790,8 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
> > > > >
> > > > > info->non_desktop = !!(quirks & EDID_QUIRK_NON_DESKTOP);
> > > > >
> > > > > + drm_get_adaptive_sync_limits(connector, edid);
> > > > > +
> > > > > DRM_DEBUG_KMS("non_desktop set to %d\n", info->non_desktop);
> > > > >
> > > > > if (edid->revision < 3)
> > > > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > > > > index 5f8c3389d46f..a27a84270d8d 100644
> > > > > --- a/include/drm/drm_connector.h
> > > > > +++ b/include/drm/drm_connector.h
> > > > > @@ -254,6 +254,26 @@ enum drm_panel_orientation {
> > > > > DRM_MODE_PANEL_ORIENTATION_RIGHT_UP,
> > > > > };
> > > > >
> > > > > +/**
> > > > > + * struct drm_adaptive_sync_info - Panel's Adaptive Sync capabilities for
> > > > > + * &drm_display_info
> > > > > + *
> > > > > + * This struct is used to store a Panel's Adaptive Sync capabilities
> > > > > + * as parsed from EDID's detailed monitor range descriptor block.
> > > > > + *
> > > > > + * @min_vfreq: This is the min supported refresh rate in Hz from
> > > > > + * EDID's detailed monitor range.
> > > > > + * @max_vfreq: This is the max supported refresh rate in Hz from
> > > > > + * EDID's detailed monitor range
> > > > > + * @pixel_clock_mhz: This is the dotclock in MHz from
> > > > > + * EDID's detailed monitor range
> > > > > + */
> > > > > +struct drm_adaptive_sync_info {
> > > > > + int min_vfreq;
> > > > > + int max_vfreq;
> > > > > + int pixel_clock_mhz;
> > > >
> > > > Any reason why these can't be unsigned? Also, does it perhaps make sense
> > > > to store the pixel clock as kHz like we do everywhere else?
> > >
> > > Aye, all typical clock frequencies should be in khz.
> > >
> > > Also the vfreqs are only u8 in the EDID, so can be u8 here as well.
> >
> > Not if you store them in kHz, they can't.
>
> IMO those can stay in Hz. That's what drm_mode_vrefresh() gives you as well.
And i kept them in hz for min and max and Mhz for pixel clock from the detailed_data_monitor_range struct
So change these all to u8?
Manasi
>
> --
> Ville Syrjälä
> Intel
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