Re: [PATCH] drm/amdgpu: extend MacBook VRAM-at-0 workaround to VERDE

[Alex Deucher]

On Fri, Sep 25, 2026 at 3:46 AM Ayhan Çiçek <ayhancicek@xxxxxxxxx> wrote:
>
> The existing MacBook workaround reserves VRAM at address 0 for
> Polaris ASICs when the iGPU is enabled. This prevents cursor
> allocations from landing at address 0.
>
> A MacBookPro11,5 with Radeon R9 M370X (VERDE) hits the same
> failure mode. Hardware cursor updates repeatedly log
> "DC: Cursor address is 0!" followed by
> "DC failed to set cursor attributes".
>
> Extend the existing workaround to CHIP_VERDE. With this change,
> hardware cursor operation is stable, the cursor errors remain at
> zero during repeated cursor movement, and cursor disappearance
> and flicker are no longer observed.

Sounds like this may be consistent for most or all Macs.  How about
something like the attached patch?

Alex

>
> Signed-off-by: Ayhan Çiçek <ayhancicek@xxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> index 1bf2a42fa..9e7f9cc2b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> @@ -1086,6 +1086,7 @@ void amdgpu_gmc_init_vga_resv_regions(struct amdgpu_device *adev)
>         case CHIP_RENOIR:
>                 adev->mman.keep_stolen_vga_memory = true;
>                 break;
> +       case CHIP_VERDE:
>         case CHIP_POLARIS10:
>         case CHIP_POLARIS11:
>         case CHIP_POLARIS12:
> --
> 2.55.0
>
From a92384b77af3818310b471c9ef0484a1a64e8166 Mon Sep 17 00:00:00 2001
From: Alex Deucher <alexander.deucher@xxxxxxx>
Date: Fri, 25 Sep 2026 09:16:26 -0400
Subject: [PATCH] drm/amdgpu: make Mac FB workaround generic

Rather than adding a case of every chip where this is seen
just check if the FB is at 0 and the ssid is apple.  This
should cover all chips which fall into this case.

Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
index 1bf2a42fa63ce..92b3221590fb6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
@@ -1086,20 +1086,17 @@ void amdgpu_gmc_init_vga_resv_regions(struct amdgpu_device *adev)
 	case CHIP_RENOIR:
 		adev->mman.keep_stolen_vga_memory = true;
 		break;
-	case CHIP_POLARIS10:
-	case CHIP_POLARIS11:
-	case CHIP_POLARIS12:
-		/* MacBookPros with switchable graphics put VRAM at 0 when
-		 * the iGPU is enabled which results in cursor issues if
-		 * the cursor ends up at 0.  Reserve vram at 0 in that case.
-		 */
-		if (adev->gmc.vram_start == 0)
-			adev->mman.keep_stolen_vga_memory = true;
-		break;
 	default:
 		adev->mman.keep_stolen_vga_memory = false;
 		break;
 	}
+	/* MacBookPros with switchable graphics put VRAM at 0 when
+	 * the iGPU is enabled which results in cursor issues if
+	 * the cursor ends up at 0.  Reserve vram at 0 in that case.
+	 */
+	if ((adev->pdev->subsystem_vendor == PCI_VENDOR_ID_APPLE) &&
+	    (adev->gmc.vram_start == 0))
+		adev->mman.keep_stolen_vga_memory = true;
 
 	if (amdgpu_sriov_vf(adev) ||
 	    !amdgpu_device_has_display_hardware(adev)) {
-- 
2.55.0