drm/vc4: Skip ULPS latching when we're in that ULPS state already.

It seems that trying to go from unlatched to unlatched will time out
waiting for STOP, and we can just skip that.

Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 16af8d2d629ccd80d99b02e3ce27fed27f8385b0..f5cf11dff45b1814752ce11d0cb7ad051888e4bf 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -838,6 +838,11 @@ static void vc4_dsi_ulps(struct vc4_dsi *dsi, bool ulps)
                         (dsi->lanes > 2 ? DSI1_STAT_PHY_D2_STOP : 0) |
                         (dsi->lanes > 3 ? DSI1_STAT_PHY_D3_STOP : 0));
        int ret;
+       bool ulps_currently_enabled = (DSI_PORT_READ(PHY_AFEC0) &
+                                      DSI_PORT_BIT(PHY_AFEC0_LATCH_ULPS));
+
+       if (ulps == ulps_currently_enabled)
+               return;
 
        DSI_PORT_WRITE(STAT, stat_ulps);
        DSI_PORT_WRITE(PHYC, DSI_PORT_READ(PHYC) | phyc_ulps);