On Tue, 11 Jun 2019, Paul Wise <pabs3@xxxxxxxxxxxxx> wrote: > On Mon, 2019-06-10 at 12:30 +0300, Jani Nikula wrote: >> We've moved the override and firmware EDID (simply "override EDID" from >> now on) handling to the low level drm_do_get_edid() function in order to >> transparently use the override throughout the stack. The idea is that >> you get the override EDID via the ->get_modes() hook. >> >> Unfortunately, there are scenarios where the DDC probe in drm_get_edid() >> called via ->get_modes() fails, although the preceding ->detect() >> succeeds. >> >> In the case reported by Paul Wise, the ->detect() hook, >> intel_crt_detect(), relies on hotplug detect, bypassing the DDC. In the >> case reported by Ilpo Järvinen, there is no ->detect() hook, which is >> interpreted as connected. The subsequent DDC probe reached via >> ->get_modes() fails, and we don't even look at the override EDID, >> resulting in no modes being added. >> >> Because drm_get_edid() is used via ->detect() all over the place, we >> can't trivially remove the DDC probe, as it leads to override EDID >> effectively meaning connector forcing. The goal is that connector >> forcing and override EDID remain orthogonal. >> >> Generally, the underlying problem here is the conflation of ->detect() >> and ->get_modes() via drm_get_edid(). The former should just detect, and >> the latter should just get the modes, typically via reading the EDID. As >> long as drm_get_edid() is used in ->detect(), it needs to retain the DDC >> probe. Or such users need to have a separate DDC probe step first. >> >> The EDID caching between ->detect() and ->get_modes() done by some >> drivers is a further complication that prevents us from making >> drm_do_get_edid() adapt to the two cases. >> >> Work around the regression by falling back to a separate attempt at >> getting the override EDID at drm_helper_probe_single_connector_modes() >> level. With a working DDC and override EDID, it'll never be called; the >> override EDID will come via ->get_modes(). There will still be a failing >> DDC probe attempt in the cases that require the fallback. >> >> v2: >> - Call drm_connector_update_edid_property (Paul) >> - Update commit message about EDID caching (Daniel) >> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107583 >> Reported-by: Paul Wise <pabs3@xxxxxxxxxxxxx> >> Cc: Paul Wise <pabs3@xxxxxxxxxxxxx> >> References: http://mid.mail-archive.com/alpine.DEB.2.20.1905262211270.24390@xxxxxxxxxxxxxxxxxxxxx >> Reported-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxx> >> Cc: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxx> >> Suggested-by: Daniel Vetter <daniel.vetter@xxxxxxxx> >> References: 15f080f08d48 ("drm/edid: respect connector force for drm_get_edid ddc probe") >> Fixes: 53fd40a90f3c ("drm: handle override and firmware EDID at drm_do_get_edid() level") >> Cc: <stable@xxxxxxxxxxxxxxx> # v4.15+ >> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> >> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> Cc: Harish Chegondi <harish.chegondi@xxxxxxxxx> >> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> >> --- >> drivers/gpu/drm/drm_edid.c | 30 ++++++++++++++++++++++++++++++ >> drivers/gpu/drm/drm_probe_helper.c | 7 +++++++ >> include/drm/drm_edid.h | 1 + >> 3 files changed, 38 insertions(+) >> >> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c >> index c59a1e8c5ada..9d8f2b952004 100644 >> --- a/drivers/gpu/drm/drm_edid.c >> +++ b/drivers/gpu/drm/drm_edid.c >> @@ -1587,6 +1587,36 @@ static struct edid *drm_get_override_edid(struct drm_connector *connector) >> return IS_ERR(override) ? NULL : override; >> } >> >> +/** >> + * drm_add_override_edid_modes - add modes from override/firmware EDID >> + * @connector: connector we're probing >> + * >> + * Add modes from the override/firmware EDID, if available. Only to be used from >> + * drm_helper_probe_single_connector_modes() as a fallback for when DDC probe >> + * failed during drm_get_edid() and caused the override/firmware EDID to be >> + * skipped. >> + * >> + * Return: The number of modes added or 0 if we couldn't find any. >> + */ >> +int drm_add_override_edid_modes(struct drm_connector *connector) >> +{ >> + struct edid *override; >> + int num_modes = 0; >> + >> + override = drm_get_override_edid(connector); >> + if (override) { >> + drm_connector_update_edid_property(connector, override); >> + num_modes = drm_add_edid_modes(connector, override); >> + kfree(override); >> + >> + DRM_DEBUG_KMS("[CONNECTOR:%d:%s] adding %d modes via fallback override/firmware EDID\n", >> + connector->base.id, connector->name, num_modes); >> + } >> + >> + return num_modes; >> +} >> +EXPORT_SYMBOL(drm_add_override_edid_modes); >> + >> /** >> * drm_do_get_edid - get EDID data using a custom EDID block read function >> * @connector: connector we're probing >> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c >> index 01e243f1ea94..ef2c468205a2 100644 >> --- a/drivers/gpu/drm/drm_probe_helper.c >> +++ b/drivers/gpu/drm/drm_probe_helper.c >> @@ -480,6 +480,13 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector, >> >> count = (*connector_funcs->get_modes)(connector); >> >> + /* >> + * Fallback for when DDC probe failed in drm_get_edid() and thus skipped >> + * override/firmware EDID. >> + */ >> + if (count == 0 && connector->status == connector_status_connected) >> + count = drm_add_override_edid_modes(connector); >> + >> if (count == 0 && connector->status == connector_status_connected) >> count = drm_add_modes_noedid(connector, 1024, 768); >> count += drm_helper_probe_add_cmdline_mode(connector); >> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h >> index 88b63801f9db..b9719418c3d2 100644 >> --- a/include/drm/drm_edid.h >> +++ b/include/drm/drm_edid.h >> @@ -478,6 +478,7 @@ struct edid *drm_get_edid_switcheroo(struct drm_connector *connector, >> struct i2c_adapter *adapter); >> struct edid *drm_edid_duplicate(const struct edid *edid); >> int drm_add_edid_modes(struct drm_connector *connector, struct edid *edid); >> +int drm_add_override_edid_modes(struct drm_connector *connector); >> >> u8 drm_match_cea_mode(const struct drm_display_mode *to_match); >> enum hdmi_picture_aspect drm_get_cea_aspect_ratio(const u8 video_code); > > Tested-by: Paul Wise <pabs3@xxxxxxxxxxxxx> > > This version looks good to me. > > Both the EDID override data and the resolution are fixed. Thanks for testing and review, pushed both to drm-misc-fixes, cc: stable v4.15. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center
