5.4-stable review patch. If anyone has any objections, please let me know.
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From: Hans Verkuil hverkuil@xs4all.nl
[ Upstream commit 6daaae5ff7f3b23a2dacc9c387ff3d4f95b67cad ]
If the hotplug detect of a display is low for longer than one second (configurable through drm_dp_cec_unregister_delay), then the CEC adapter is unregistered since we assume the display was disconnected. If the HPD went low for less than one second, then we check if the properties of the CEC adapter have changed, since that indicates that we actually switch to new hardware and we have to unregister the old CEC device and register a new one.
Unfortunately, the test for changed properties was written poorly, and after a new CEC capability was added to the CEC core code the test always returned true (i.e. the properties had changed).
As a result the CEC device was unregistered and re-registered for every HPD toggle. If the CEC remote controller integration was also enabled (CONFIG_MEDIA_CEC_RC was set), then the corresponding input device was also unregistered and re-registered. As a result the input device in /sys would keep incrementing its number, e.g.:
/sys/devices/pci0000:00/0000:00:08.1/0000:e7:00.0/rc/rc0/input20
Since short HPD toggles are common, the number could over time get into the thousands.
While not a serious issue (i.e. nothing crashes), it is not intended to work that way.
This patch changes the test so that it only checks for the single CEC capability that can actually change, and it ignores any other capabilities, so this is now safe as well if new caps are added in the future.
With the changed test the bit under #ifndef CONFIG_MEDIA_CEC_RC can be dropped as well, so that's a nice cleanup.
Signed-off-by: Hans Verkuil hverkuil@xs4all.nl Reported-by: Farblos farblos@vodafonemail.de Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Fixes: 2c6d1fffa1d9 ("drm: add support for DisplayPort CEC-Tunneling-over-AUX") Tested-by: Farblos farblos@vodafonemail.de Link: https://patchwork.freedesktop.org/patch/msgid/361bb03d-1691-4e23-84da-0861ea... Signed-off-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/drm_dp_cec.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c index b15cee85b702b..2b66804044f89 100644 --- a/drivers/gpu/drm/drm_dp_cec.c +++ b/drivers/gpu/drm/drm_dp_cec.c @@ -303,16 +303,6 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid) if (!aux->transfer) return;
-#ifndef CONFIG_MEDIA_CEC_RC - /* - * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by - * cec_allocate_adapter() if CONFIG_MEDIA_CEC_RC is undefined. - * - * Do this here as well to ensure the tests against cec_caps are - * correct. - */ - cec_caps &= ~CEC_CAP_RC; -#endif cancel_delayed_work_sync(&aux->cec.unregister_work);
mutex_lock(&aux->cec.lock); @@ -329,7 +319,9 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid) num_las = CEC_MAX_LOG_ADDRS;
if (aux->cec.adap) { - if (aux->cec.adap->capabilities == cec_caps && + /* Check if the adapter properties have changed */ + if ((aux->cec.adap->capabilities & CEC_CAP_MONITOR_ALL) == + (cec_caps & CEC_CAP_MONITOR_ALL) && aux->cec.adap->available_log_addrs == num_las) { /* Unchanged, so just set the phys addr */ cec_s_phys_addr_from_edid(aux->cec.adap, edid);