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.
v2:
- Check mmio_remap bus address (adev->rmmio_remap.bus_addr) instead of
rmmio_base. (Alex)
- Skip quietly if PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE or no bus address
(no warn). (Alex)
- Use `amdgpu_bo_create()` (not *_kernel) - Only with this The object
is stored in adev->mmio_remap.bo and will later be exposed to
userspace via a GEM handle. (Christian)
Suggested-by: 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 | 64 +++++++++++++++++++++++++
1 file changed, 64 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 7822d8969c9f..0e301cab74e0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1853,6 +1853,63 @@ 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 a one-page (4K) GEM BO in AMDGPU_GEM_DOMAIN_MMIO_REMAP when the
+ * hardware exposes a remap base (adev->rmmio_remap.bus_addr) and the host
+ * PAGE_SIZE is <= AMDGPU_GPU_PAGE_SIZE (4K). The BO is created as a regular
+ * GEM object (amdgpu_bo_create), then reserved and kmap’ed once to exercise
+ * the io-mem setup path. If prerequisites are not met, this is a no-op.
+ *
+ * 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;
+ struct amdgpu_bo_param bp = { 0 };
+ void *kptr;
+
+ /* Skip if HW doesn’t expose remap or system PAGE > GPU 4K */
+ if (!adev->rmmio_remap.bus_addr || PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE)
+ return 0;
+
+ /* Hardware remap page is fixed 4K; skip on larger PAGE_SIZE. */
+ if (PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE)
+ return 0;
+
+ /* Create exactly one GEM BO in the MMIO_REMAP domain. */
+ bp.type = ttm_bo_type_device; /* userspace-mappable GEM
*/
+ bp.size = AMDGPU_GPU_PAGE_SIZE; /* 4K */
+ bp.byte_align = AMDGPU_GPU_PAGE_SIZE;
+ bp.domain = AMDGPU_GEM_DOMAIN_MMIO_REMAP;
+ bp.flags = 0;
+ bp.resv = NULL;
+ bp.bo_ptr_size = sizeof(struct amdgpu_bo);
+
+ r = amdgpu_bo_create(adev, &bp, &adev->rmmio_remap.bo);
+ if (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)
+{
+ amdgpu_bo_unref(&adev->rmmio_remap.bo);
+ adev->mmio_remap.bo = NULL;
+}
+
/*
* amdgpu_ttm_init - Init the memory management (ttm) as well as various
* gtt/vram related fields.
@@ -2027,6 +2084,11 @@ 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 +2152,8 @@ 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
