From 04757d0e37897cdfa59050157b9083d661bd099e Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Mon, 10 Jun 2019 12:30:54 +0300 Subject: [PATCH] drm: add fallback override/firmware EDID modes workaround MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Paul Wise References: http://mid.mail-archive.com/alpine.DEB.2.20.1905262211270.24390@whs-18.cs.helsinki.fi Reported-by: Ilpo Järvinen Cc: Ilpo Järvinen Suggested-by: Daniel Vetter 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: # v4.15+ 56a2b7f2a39a drm/edid: abstract override/firmware EDID retrieval Cc: # v4.15+ Cc: Daniel Vetter Cc: Ville Syrjälä Cc: Harish Chegondi Tested-by: Paul Wise Reviewed-by: Daniel Vetter Signed-off-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/20190610093054.28445-1-jani.nikula@intel.com Signed-off-by: Greg Kroah-Hartman --- 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 a6ddd6a3869f4..5965f6383ada3 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -1594,6 +1594,36 @@ 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 a1bb157bfdfae..d18b7e27ef64c 100644 --- 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); diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h index e3c4048331156..53be104aab5ce 100644 --- a/include/drm/drm_edid.h +++ b/include/drm/drm_edid.h @@ -466,6 +466,7 @@ 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); -- 2.39.2