[v2] drm/amdgpu: Add DC feature mask to disable fractional pwm
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Message ID 20191021194414.24627-1-sunpeng.li@amd.com
State New
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  • [v2] drm/amdgpu: Add DC feature mask to disable fractional pwm
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Commit Message

Leo Oct. 21, 2019, 7:44 p.m. UTC
From: Leo Li <sunpeng.li@amd.com>

[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>
---

v2: Add bugzilla link

 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(+)

Comments

Koo, Anthony Oct. 22, 2019, 2:15 p.m. UTC | #1
Reviewed-by: Anthony Koo <anthony.koo@amd.com>

-----Original Message-----
From: sunpeng.li@amd.com <sunpeng.li@amd.com> 
Sent: Monday, October 21, 2019 3:44 PM
To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; lskrejci@gmail.com
Cc: Koo, Anthony <Anthony.Koo@amd.com>; Wentland, Harry <Harry.Wentland@amd.com>; Li, Sun peng (Leo) <Sunpeng.Li@amd.com>
Subject: [PATCH v2] drm/amdgpu: Add DC feature mask to disable fractional pwm

From: Leo Li <sunpeng.li@amd.com>

[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>
---

v2: Add bugzilla link

 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 1cf4beb76835..73f917d4d1e1 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -728,6 +728,9 @@ 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 d759fdca7fdb..b8a3fc505c9b 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;
--
2.23.0
Lukáš Krejčí Oct. 23, 2019, 2:19 p.m. UTC | #2
On Mon, 2019-10-21 at 15:44 -0400, sunpeng.li@amd.com wrote:
> From: Leo Li <sunpeng.li@amd.com>
> 
> [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>
> ---
> 
> v2: Add bugzilla link
> 
>  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(+)

Tested on Ubuntu 19.04, vanilla v5.3.7 kernel with the patch applied
and amdgpu.dcfeaturemask=0x4 added to the kernel command line, no
issues after 8 reboots. (The issue could be reproduced without
amdgpu.dcfeaturemask=0x4 on first boot.)

Tested-by: Lukáš Krejčí <lskrejci@gmail.com>
Leo Oct. 23, 2019, 3:53 p.m. UTC | #3
On 2019-10-23 10:19 a.m., Lukáš Krejčí wrote:
> On Mon, 2019-10-21 at 15:44 -0400, sunpeng.li@amd.com wrote:
>> From: Leo Li <sunpeng.li@amd.com>
>>
>> [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>
>> ---
>>
>> v2: Add bugzilla link
>>
>>  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(+)
> 
> Tested on Ubuntu 19.04, vanilla v5.3.7 kernel with the patch applied
> and amdgpu.dcfeaturemask=0x4 added to the kernel command line, no
> issues after 8 reboots. (The issue could be reproduced without
> amdgpu.dcfeaturemask=0x4 on first boot.)
> 
> Tested-by: Lukáš Krejčí <lskrejci@gmail.com>

Applied, thanks!
Leo

Patch
diff mbox series

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 1cf4beb76835..73f917d4d1e1 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -728,6 +728,9 @@  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 d759fdca7fdb..b8a3fc505c9b 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;