Add amdgpu_ttm_mmio_remap_bo_init()/fini() to manage the kernel-owned
one-page(4K) MMIO_REMAP BO. The allocator runs during TTM init when the
hardware exposes a remap base (adev->rmmio_base) and the host
PAGE_SIZE is <= AMDGPU_GPU_PAGE_SIZE (4K).
The helper is idempotent (returns 0 if already allocated) and only
returns an error when the actual allocation fails.
This keeps MMIO_REMAP lifetime handling localized and prepares for the
subsequent patch that exposes a userspace handle.
Cc: Christian König <christian.koe...@amd.com>
Suggested-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 69 +++++++++++++++++++++++++
1 file changed, 69 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 58b6ab1be4c1..c76c41a312b0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1853,6 +1853,68 @@ static void amdgpu_ttm_pools_fini(struct amdgpu_device
*adev)
adev->mman.ttm_pools = NULL;
}
+/**
+ * amdgpu_ttm_mmio_remap_bo_init - allocate the singleton 4K MMIO_REMAP BO
+ * @adev: amdgpu device
+ *
+ * Allocates the kernel-owned one-page buffer in AMDGPU_GEM_DOMAIN_MMIO_REMAP
+ * when the hardware exposes a remap base (adev->rmmio_remap.base) and the host
+ * PAGE_SIZE is <= AMDGPU_GPU_PAGE_SIZE (4K). If either condition is not met,
the
+ * function returns 0 and leaves adev->rmmio_remap.bo as NULL.
+ *
+ * If the BO is already allocated, the function does nothing and returns 0.
+ * Only errors during actual allocation (e.g., amdgpu_bo_create_kernel()) are
+ * propagated as negative returns.
+ *
+ * Return:
+ * * 0 on success or intentional skip (feature not present/unsupported)
+ * * negative errno on allocation failure
+ */
+static int amdgpu_ttm_mmio_remap_bo_init(struct amdgpu_device *adev)
+{
+ int r;
+
+ if (!adev->rmmio_base)
+ return 0;
+
+ /* Hardware remap page is fixed 4K; skip on larger PAGE_SIZE. */
+ if (PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE) {
+ dev_warn(adev->dev, "MMIO_REMAP disabled: PAGE_SIZE=%lu >
4K\n", PAGE_SIZE);
+ return 0;
+ }
+
+ if (adev->rmmio_remap.bo)
+ return 0;
+
+ /* Create exactly ONE kernel-owned BO in the MMIO_REMAP domain */
+ r = amdgpu_bo_create_kernel(adev,
+ AMDGPU_GPU_PAGE_SIZE, AMDGPU_GPU_PAGE_SIZE,
+ AMDGPU_GEM_DOMAIN_MMIO_REMAP,
+ &adev->rmmio_remap.bo,
+ NULL, NULL);
+ if (r) {
+ dev_err(adev->dev, "MMIO_REMAP: BO create failed (%d)\n", r);
+ return r;
+ }
+
+ return 0;
+}
+
+/**
+ * amdgpu_ttm_mmio_remap_bo_fini - free the singleton MMIO_REMAP BO
+ * @adev: amdgpu device
+ *
+ * Frees the kernel-owned MMIO_REMAP BO if it was allocated by
+ * amdgpu_ttm_mmio_remap_bo_init().
+ */
+static void amdgpu_ttm_mmio_remap_bo_fini(struct amdgpu_device *adev)
+{
+ if (adev->rmmio_remap.bo) {
+ amdgpu_bo_free_kernel(&adev->rmmio_remap.bo, NULL, NULL);
+ adev->rmmio_remap.bo = NULL;
+ }
+}
+
/*
* amdgpu_ttm_init - Init the memory management (ttm) as well as various
* gtt/vram related fields.
@@ -2027,6 +2089,11 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
return r;
}
+ /* Allocate the singleton MMIO_REMAP BO (4K) if supported */
+ r = amdgpu_ttm_mmio_remap_bo_init(adev);
+ if (r)
+ return r;
+
/* Initialize preemptible memory pool */
r = amdgpu_preempt_mgr_init(adev);
if (r) {
@@ -2090,6 +2157,8 @@ void amdgpu_ttm_fini(struct amdgpu_device *adev)
amdgpu_bo_free_kernel(&adev->mman.sdma_access_bo, NULL,
&adev->mman.sdma_access_ptr);
+ /* Drop the singleton MMIO_REMAP BO (if allocated) */
+ amdgpu_ttm_mmio_remap_bo_fini(adev);
amdgpu_ttm_fw_reserve_vram_fini(adev);
amdgpu_ttm_drv_reserve_vram_fini(adev);
--
2.34.1
