[PATCH] drm/amd/display: update bios scratch when setting backlight

[Alex Deucher]

Update the bios scratch register when updating the backlight
level.  Some platforms apparently read this scratch register
and do additional operations in their hotkey handlers.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1518
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c      | 12 ++++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h      |  2 ++
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  4 ++++
 3 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
index 96b7bb13a2dd..12a6b1c99c93 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
@@ -1569,6 +1569,18 @@ void amdgpu_atombios_scratch_regs_engine_hung(struct amdgpu_device *adev,
 	WREG32(adev->bios_scratch_reg_offset + 3, tmp);
 }
 
+void amdgpu_atombios_scratch_regs_set_backlight_level(struct amdgpu_device *adev,
+						      u32 backlight_level)
+{
+	u32 tmp = RREG32(adev->bios_scratch_reg_offset + 2);
+
+	tmp &= ~ATOM_S2_CURRENT_BL_LEVEL_MASK;
+	tmp |= (backlight_level << ATOM_S2_CURRENT_BL_LEVEL_SHIFT) &
+		ATOM_S2_CURRENT_BL_LEVEL_MASK;
+
+	WREG32(adev->bios_scratch_reg_offset + 2, tmp);
+}
+
 bool amdgpu_atombios_scratch_need_asic_init(struct amdgpu_device *adev)
 {
 	u32 tmp = RREG32(adev->bios_scratch_reg_offset + 7);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h
index 8cc0222dba19..27e74b1fc260 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h
@@ -185,6 +185,8 @@ bool amdgpu_atombios_has_gpu_virtualization_table(struct amdgpu_device *adev);
 void amdgpu_atombios_scratch_regs_lock(struct amdgpu_device *adev, bool lock);
 void amdgpu_atombios_scratch_regs_engine_hung(struct amdgpu_device *adev,
 					      bool hung);
+void amdgpu_atombios_scratch_regs_set_backlight_level(struct amdgpu_device *adev,
+						      u32 backlight_level);
 bool amdgpu_atombios_scratch_need_asic_init(struct amdgpu_device *adev);
 
 void amdgpu_atombios_copy_swap(u8 *dst, u8 *src, u8 num_bytes, bool to_le);
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 40a4269770fa..05e4a0952a2b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -51,6 +51,7 @@
 #include <drm/drm_hdcp.h>
 #endif
 #include "amdgpu_pm.h"
+#include "amdgpu_atombios.h"
 
 #include "amd_shared.h"
 #include "amdgpu_dm_irq.h"
@@ -3918,6 +3919,9 @@ static int amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
 	caps = dm->backlight_caps[bl_idx];
 
 	dm->brightness[bl_idx] = user_brightness;
+	/* update scratch register */
+	if (bl_idx == 0)
+		amdgpu_atombios_scratch_regs_set_backlight_level(dm->adev, dm->brightness[bl_idx]);
 	brightness = convert_brightness_from_user(&caps, dm->brightness[bl_idx]);
 	link = (struct dc_link *)dm->backlight_link[bl_idx];
 
-- 
2.31.1