linux-kernel - [PATCH v3 2/6] drm/msm: add support for per-CRTC max_vblank

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Date:   Fri, 31 May 2019 05:46:15 -0400
From:   Brian Masney <masneyb@...tation.org>
To:     robdclark@...il.com, sean@...rly.run,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, airlied@...ux.ie, daniel@...ll.ch,
        linux-kernel@...r.kernel.org, linus.walleij@...aro.org,
        jonathan@...ek.ca, robh@...nel.org, jeffrey.l.hugo@...il.com
Subject: [PATCH v3 2/6] 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.

Signed-off-by: Brian Masney <masneyb@...tation.org>
Suggested-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>
---
 drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c | 16 +++++++++++++++-
 drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c  |  2 +-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
index c3751c95b452..6fde1097844f 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
+++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
@@ -450,6 +450,18 @@ static void mdp5_crtc_atomic_disable(struct drm_crtc *crtc,
 	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)
 {
@@ -486,7 +498,7 @@ static void mdp5_crtc_atomic_enable(struct drm_crtc *crtc,
 	}
 
 	/* Restore vblank irq handling after power is enabled */
-	drm_crtc_vblank_on(crtc);
+	mdp5_crtc_vblank_on(crtc);
 
 	mdp5_crtc_mode_set_nofb(crtc);
 
@@ -1039,6 +1051,8 @@ static void mdp5_crtc_reset(struct drm_crtc *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 = {
diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
index 97179bec8902..fcb0b0455abe 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
+++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
@@ -750,7 +750,7 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
 	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;
-- 
2.20.1