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From f247d4a6fe42acc60b775457e3c35b8289532590 Mon Sep 17 00:00:00 2001
From: Leo Li <sunpeng.li@amd.com>
Date: Mon, 21 Oct 2019 14:58:47 -0400
Subject: [PATCH 14/16] drm/amdgpu: Add DC feature mask to disable fractional
 pwm
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

[Why]

Some LED panel drivers might not like fractional PWM. In such cases,
backlight flickering may be observed.

[How]

Add a DC feature mask to disable fractional PWM, and associate it with
the preexisting dc_config flag.

The flag is only plumbed through the dmcu firmware, so plumb it through
the driver path as well.

To disable, add the following to the linux cmdline:
amdgpu.dcfeaturemask=0x4

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204957
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Anthony Koo <anthony.koo@amd.com>
Tested-by: Lukáš Krejčí <lskrejci@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +++
 drivers/gpu/drm/amd/display/dc/dce/dce_abm.c      | 4 ++++
 drivers/gpu/drm/amd/include/amd_shared.h          | 1 +
 3 files changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 4e9c15c409ba..25b72eb76add 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -697,6 +697,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 	if (amdgpu_dc_feature_mask & DC_MULTI_MON_PP_MCLK_SWITCH_MASK)
 		init_data.flags.multi_mon_pp_mclk_switch = true;
 
+	if (amdgpu_dc_feature_mask & DC_DISABLE_FRACTIONAL_PWM_MASK)
+		init_data.flags.disable_fractional_pwm = true;
+
 	init_data.flags.power_down_display_on_boot = true;
 
 #ifdef CONFIG_DRM_AMD_DC_DCN2_0
diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c b/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c
index 7700a855d77c..698b84acc44f 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_abm.c
@@ -404,6 +404,10 @@ static bool dce_abm_init_backlight(struct abm *abm)
 	/* Enable the backlight output */
 	REG_UPDATE(BL_PWM_CNTL, BL_PWM_EN, 1);
 
+	/* Disable fractional pwm if configured */
+	REG_UPDATE(BL_PWM_CNTL, BL_PWM_FRACTIONAL_EN,
+		   abm->ctx->dc->config.disable_fractional_pwm ? 0 : 1);
+
 	/* Unlock group 2 backlight registers */
 	REG_UPDATE(BL_PWM_GRP1_REG_LOCK,
 			BL_PWM_GRP1_REG_LOCK, 0);
diff --git a/drivers/gpu/drm/amd/include/amd_shared.h b/drivers/gpu/drm/amd/include/amd_shared.h
index 8889aaceec60..5450ed762b7a 100644
--- a/drivers/gpu/drm/amd/include/amd_shared.h
+++ b/drivers/gpu/drm/amd/include/amd_shared.h
@@ -143,6 +143,7 @@ enum PP_FEATURE_MASK {
 enum DC_FEATURE_MASK {
 	DC_FBC_MASK = 0x1,
 	DC_MULTI_MON_PP_MCLK_SWITCH_MASK = 0x2,
+	DC_DISABLE_FRACTIONAL_PWM_MASK = 0x4,
 };
 
 enum amd_dpm_forced_level;
-- 
2.25.0