drm/vc4: crtc: Increase setup cost in core clock calculation to handle extreme reduce...

The formula that determines the core clock requirement based on pixel
clock and blanking has been determined experimentally to minimise the
clock while supporting all modes we've seen.

A new reduced blanking mode (4kp60 at 533MHz rather than the standard
594MHz) has been seen that doesn't produce a high enough clock and
results in "flip_done timed out" error.

Increase the setup cost in the formula to make this work. The result is
a reduced blanking mode increases by up to 7MHz while leaving the
standard timing
mode untouched

Link: https://github.com/raspberrypi/linux/issues/4446
Fixes: 16e101051f32 ("drm/vc4: Increase the core clock based on HVS load")
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20230127145558.446123-1-maxime@cerno.tech

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 0108613e79d53ce6b110491dcba3ec0991561cfe..7258975331ca71a81326b84f7d487069801d96dc 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -711,7 +711,7 @@ static int vc4_crtc_atomic_check(struct drm_crtc *crtc,
                struct vc4_encoder *vc4_encoder = to_vc4_encoder(encoder);
 
                if (vc4_encoder->type == VC4_ENCODER_TYPE_HDMI0) {
-                       vc4_state->hvs_load = max(mode->clock * mode->hdisplay / mode->htotal + 1000,
+                       vc4_state->hvs_load = max(mode->clock * mode->hdisplay / mode->htotal + 8000,
                                                  mode->clock * 9 / 10) * 1000;
                } else {
                        vc4_state->hvs_load = mode->clock * 1000;