On Mon, Jun 17, 2019 at 01:52:47PM +0300, Jani Nikula wrote:
On Sat, 15 Jun 2019, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 5.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 48eaeb7664c76139438724d520a1ea4a84a3ed92 Mon Sep 17 00:00:00 2001 From: Jani Nikula jani.nikula@intel.com 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=UTF-8 Content-Transfer-Encoding: 8bit
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 References: http://mid.mail-archive.com/alpine.DEB.2.20.1905262211270.24390@whs-18.cs.he... 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 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@vger.kernel.org # v4.15+ 56a2b7f2a39a drm/edid: abstract override/firmware EDID retrieval
I was hoping this dependency description would suffice; does it not work if you pick that up first? Ditto for the other stable kernels.
Ugh, sorry, I missed that.
Now picked up both patches, thanks!
greg k-h