From: Jani Nikula jani.nikula@intel.com
commit 48eaeb7664c76139438724d520a1ea4a84a3ed92 upstream.
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@bonedaddy.net Cc: Paul Wise pabs3@bonedaddy.net Reported-by: Ilpo Järvinen ilpo.jarvinen@cs.helsinki.fi Cc: Ilpo Järvinen ilpo.jarvinen@cs.helsinki.fi Suggested-by: Daniel Vetter daniel.vetter@ffwll.ch Fixes: 53fd40a90f3c ("drm: handle override and firmware EDID at drm_do_get_edid() level") Cc: stable@vger.kernel.org # v4.15+ 56a2b7f2a39a drm/edid: abstract override/firmware EDID retrieval Cc: stable@vger.kernel.org # v4.15+ Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harish Chegondi harish.chegondi@intel.com Tested-by: Paul Wise pabs3@bonedaddy.net Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Jani Nikula jani.nikula@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20190610093054.28445-1-jani.ni... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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(+)
--- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -1595,6 +1595,36 @@ static struct edid *drm_get_override_edi }
/** + * 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 * @get_edid_block: EDID block read function --- a/drivers/gpu/drm/drm_probe_helper.c +++ b/drivers/gpu/drm/drm_probe_helper.c @@ -479,6 +479,13 @@ retry:
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); --- a/include/drm/drm_edid.h +++ b/include/drm/drm_edid.h @@ -465,6 +465,7 @@ struct edid *drm_get_edid_switcheroo(str 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);