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authorThierry Reding <treding@nvidia.com>2014-06-27 17:19:25 +0200
committerDave Airlie <airlied@redhat.com>2014-07-08 11:31:36 +1000
commite2215321ff180f280d83837f57f3a84f8b6dda0d (patch)
tree0e9be5ad6887e1317208ca03e7c524c075f04b96 /include
parent10a231026574f9ec9761b6435394b8830b485e4e (diff)
drm/tegra: Implement race-free hotplug detection
A race condition currently exists on Tegra, where it can happen that a monitor attached via HDMI isn't detected during the initial FB helper setup, but the hotplug event happens too early to be processed by the poll helpers because they haven't been initialized yet. This happens because on some boards the HDMI driver can control the regulator that supplies the +5V pin on the HDMI connector. Therefore depending on the timing between the initialization of the HDMI driver and the rest of DRM, it's possible that the monitor returns the hotplug signal right within the window where we would miss it. Unfortunately, drm_kms_helper_poll_init() will wreak havoc when called before at least some parts of the FB helpers have been set up. This commit fixes this by splitting out the minimum of initialization required to make drm_kms_helper_poll_init() work into a separate function that can be called early. It is then safe to move all of the poll helper initialization to an earlier point in time (before the HDMI output driver has a chance to enable the +5V supply). That way if the hotplug signal is returned before the initial FB helper setup, the monitor will be forcefully detected at that point, and if the hotplug signal is returned after that it will be properly handled by the poll helpers. Signed-off-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Dave Airlie <airlied@redhat.com>
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