From d984fd8907736d37656c558e213cfe087e43a7ce Mon Sep 17 00:00:00 2001 From: Dom Cobley Date: Mon, 12 Aug 2024 13:31:58 +0100 Subject: [PATCH 1225/1350] drm/vc4: Add a delay after disabling hdmi phy output There appears to be a requirement for some devices (I'm testing with a 8K VRROOM 40Gbps HDMI switch) for a measable delay between removing the hdmi phy output from the old mode, to enabling the hdmi phy output for the new mode. Without the delay, a mode switch has a small change of getting a permanent 'no signal', which requires a subsequent mode switch or a unplug/replug to redetect. Switching between 4kp24/25/30 modes fails about 5% of time in my testing. Add a delay to make it impossible to switch faster than this. Signed-off-by: Dom Cobley --- drivers/gpu/drm/vc4/vc4_crtc.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/gpu/drm/vc4/vc4_crtc.c +++ b/drivers/gpu/drm/vc4/vc4_crtc.c @@ -668,6 +668,7 @@ static void vc4_crtc_atomic_disable(stru * someone was waiting it. */ vc4_crtc_send_vblank(crtc); + msleep(20); } static void vc4_crtc_atomic_enable(struct drm_crtc *crtc,