drm/msm: add support for per-CRTC max_vblank_count on mdp5

The mdp5 drm/kms driver currently does not work on command-mode DSI
panels due to 'vblank wait timed out' errors. This causes a latency
of seconds, or tens of seconds in some cases, before content is shown
on the panel. This hardware does not have the something that we can use
as a frame counter available when running in command mode, so we need to
fall back to using timestamps by setting the max_vblank_count to zero.
This can be done on a per-CRTC basis, so the convert mdp5 to use
drm_crtc_set_max_vblank_count().

This change was tested on a LG Nexus 5 (hammerhead) phone.

Suggested-by: Jeffrey Hugo <[e-mail]>
Reviewed-by: Jeffrey Hugo <[e-mail]>
Signed-off-by: Brian Masney <[e-mail]>
Signed-off-by: Sean Paul <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c

···
 	mdp5_crtc->enabled = false;
 }
 
+static void mdp5_crtc_vblank_on(struct drm_crtc *crtc)
+{
+	struct mdp5_crtc_state *mdp5_cstate = to_mdp5_crtc_state(crtc->state);
+	struct mdp5_interface *intf = mdp5_cstate->pipeline.intf;
+	u32 count;
+
+	count = intf->mode == MDP5_INTF_DSI_MODE_COMMAND ? 0 : 0xffffffff;
+	drm_crtc_set_max_vblank_count(crtc, count);
+
+	drm_crtc_vblank_on(crtc);
+}
+
 static void mdp5_crtc_atomic_enable(struct drm_crtc *crtc,
 				    struct drm_crtc_state *old_state)
 {
···
 	}
 
 	/* Restore vblank irq handling after power is enabled */
-	drm_crtc_vblank_on(crtc);
+	mdp5_crtc_vblank_on(crtc);
 
 	mdp5_crtc_mode_set_nofb(crtc);
 
···
 		mdp5_crtc_destroy_state(crtc, crtc->state);
 
 	__drm_atomic_helper_crtc_reset(crtc, &mdp5_cstate->base);
+
+	drm_crtc_vblank_reset(crtc);
 }
 
 static const struct drm_crtc_funcs mdp5_crtc_funcs = {

drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c

···
 	dev->driver->get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos;
 	dev->driver->get_scanout_position = mdp5_get_scanoutpos;
 	dev->driver->get_vblank_counter = mdp5_get_vblank_counter;
-	dev->max_vblank_count = 0xffffffff;
+	dev->max_vblank_count = 0; /* max_vblank_count is set on each CRTC */
 	dev->vblank_disable_immediate = true;
 
 	return kms;