linux-kernel - [PATCH] drm/radeon/dpm: Disable sclk switching when two 4K 60Hz monitors are connected

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Message-Id: <20210429133941.531730-1-kai.heng.feng@canonical.com>
Date:   Thu, 29 Apr 2021 21:39:40 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     alexander.deucher@....com, christian.koenig@....com
Cc:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        amd-gfx@...ts.freedesktop.org (open list:RADEON and AMDGPU DRM DRIVERS),
        dri-devel@...ts.freedesktop.org (open list:DRM DRIVERS),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/radeon/dpm: Disable sclk switching when two 4K 60Hz monitors are connected

Screen flickers rapidly when two 4K 60Hz monitors are connected to an
Oland card. This issue doesn't happen when one monitor is 4K 60Hz
(pixelclock 594MHz) and another one is 4K 30Hz (pixelclock 297MHz).

The issue is gone after setting "power_dpm_force_performance_level" to
"high". Following the lead, we found that the issue only occurs when
sclk is too low.

So resolve the issue by disabling sclk switching when there are two
monitors that requires high pixelclock (> 297MHz).

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
 drivers/gpu/drm/radeon/radeon.h    | 1 +
 drivers/gpu/drm/radeon/radeon_pm.c | 8 ++++++++
 drivers/gpu/drm/radeon/si_dpm.c    | 3 +++
 3 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index 42281fce552e6..56ed5634cebef 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -1549,6 +1549,7 @@ struct radeon_dpm {
 	void                    *priv;
 	u32			new_active_crtcs;
 	int			new_active_crtc_count;
+	int			high_pixelclock_count;
 	u32			current_active_crtcs;
 	int			current_active_crtc_count;
 	bool single_display;
diff --git a/drivers/gpu/drm/radeon/radeon_pm.c b/drivers/gpu/drm/radeon/radeon_pm.c
index 0c1950f4e146f..3861c0b98fcf3 100644
--- a/drivers/gpu/drm/radeon/radeon_pm.c
+++ b/drivers/gpu/drm/radeon/radeon_pm.c
@@ -1767,6 +1767,7 @@ static void radeon_pm_compute_clocks_dpm(struct radeon_device *rdev)
 	struct drm_device *ddev = rdev->ddev;
 	struct drm_crtc *crtc;
 	struct radeon_crtc *radeon_crtc;
+	struct radeon_connector *radeon_connector;
 
 	if (!rdev->pm.dpm_enabled)
 		return;
@@ -1776,6 +1777,7 @@ static void radeon_pm_compute_clocks_dpm(struct radeon_device *rdev)
 	/* update active crtc counts */
 	rdev->pm.dpm.new_active_crtcs = 0;
 	rdev->pm.dpm.new_active_crtc_count = 0;
+	rdev->pm.dpm.high_pixelclock_count = 0;
 	if (rdev->num_crtc && rdev->mode_info.mode_config_initialized) {
 		list_for_each_entry(crtc,
 				    &ddev->mode_config.crtc_list, head) {
@@ -1783,6 +1785,12 @@ static void radeon_pm_compute_clocks_dpm(struct radeon_device *rdev)
 			if (crtc->enabled) {
 				rdev->pm.dpm.new_active_crtcs |= (1 << radeon_crtc->crtc_id);
 				rdev->pm.dpm.new_active_crtc_count++;
+				if (!radeon_crtc->connector)
+					continue;
+
+				radeon_connector = to_radeon_connector(radeon_crtc->connector);
+				if (radeon_connector->pixelclock_for_modeset > 297000)
+					rdev->pm.dpm.high_pixelclock_count++;
 			}
 		}
 	}
diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c
index 9186095518047..be6fa3257d1bc 100644
--- a/drivers/gpu/drm/radeon/si_dpm.c
+++ b/drivers/gpu/drm/radeon/si_dpm.c
@@ -2995,6 +2995,9 @@ static void si_apply_state_adjust_rules(struct radeon_device *rdev,
 	    ni_dpm_vblank_too_short(rdev))
 		disable_mclk_switching = true;
 
+	if (rdev->pm.dpm.high_pixelclock_count > 1)
+		disable_sclk_switching = true;
+
 	if (rps->vclk || rps->dclk) {
 		disable_mclk_switching = true;
 		disable_sclk_switching = true;
-- 
2.30.2