Re: [PATCH 6/6] drm/amdgpu: Use memset32 for SDMA padding

Thu, 10 Sep 2026 08:33:50 -0700 


On 09/09/2026 19:37, Timur Kristóf wrote:

On 2026. szeptember 9., szerda 12:52:15 közép-európai nyári idő Tvrtko Ursulin
wrote:

Instead of open coding it via the inefficient amdgpu_ring_write(), which
which the compiler is not able to optimise much, we can add a new
amdgpu_ring_fill() helper which pads using memset32.


Can you elaborate more on that? It seems to me that amdgpu_ring_insert_nop()
already uses memset32() so I don't see how the commit improves it.



I created some confusion by rewriting the commit text. This is an old 
patch I remembered I had laying around. First time I posted it was 
around July 2024 believe it or not. Yesterday I cherry-picked it and 
tried to update the commit but messed up. Did not account for changes 
which landed since. Will fix.


Regards,

Tvrtko



We convert the amdgpu_ring_insert_nop() used by the GFX rings and also
the SDMA ones.


As far as I see amdgpu_ring_insert_nop() is used by all rings not just GFX and
SDMA, isn't it?


Although with SDMA this should have much less benefit than
with GFX (only SDMA v4.0 uses the 256 byte ring padding while the rest use
16), but on the other hand it should not harm and is at least more
consistent.

Signed-off-by: Tvrtko Ursulin <[email protected]>
Cc: Timur Kristóf <[email protected]>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 17 +---------------
  drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 26 ++++++++++++++++++++++++
  drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c   | 15 +++++++-------
  drivers/gpu/drm/amd/amdgpu/sdma_v7_1.c   | 15 +++++++-------
  11 files changed, 90 insertions(+), 88 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c index 686c92e96025..38434a4c3566
100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -117,22 +117,7 @@ int amdgpu_ring_alloc(struct amdgpu_ring *ring,
unsigned int ndw) */
  void amdgpu_ring_insert_nop(struct amdgpu_ring *ring, uint32_t count)
  {
-       uint32_t occupied, chunk1, chunk2;
-
-       occupied = ring->wptr & ring->buf_mask;
-       chunk1 = ring->buf_mask + 1 - occupied;
-       chunk1 = (chunk1 >= count) ? count : chunk1;
-       chunk2 = count - chunk1;
-
-       if (chunk1)
-               memset32(&ring->ring[occupied], ring->funcs->nop,

chunk1);

-
-       if (chunk2)
-               memset32(ring->ring, ring->funcs->nop, chunk2);
-
-       ring->wptr += count;
-       ring->wptr &= ring->ptr_mask;
-       ring->count_dw -= count;
+       amdgpu_ring_fill(ring, ring->funcs->nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h index 6b6ee4083c8d..2b1d3956cdd3
100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
@@ -522,6 +522,32 @@ static inline void amdgpu_ring_write_multiple(struct
amdgpu_ring *ring, ring->count_dw -= count_dw;
  }

+static inline void amdgpu_ring_fill(struct amdgpu_ring *ring,
+                                   u32 val, u32 count)
+{
+       const u32 buf_mask = ring->buf_mask;
+       u32 occupied, chunk1, chunk2;
+       u64 wptr = ring->wptr;
+
+       if (count == 0)
+               return;
+
+       occupied = wptr & buf_mask;
+       chunk1 = buf_mask + 1 - occupied;
+       chunk1 = (chunk1 >= count) ? count : chunk1;
+       chunk2 = count - chunk1;
+
+       if (chunk1)
+               memset32(&ring->ring[occupied], val, chunk1);
+
+       if (chunk2)
+               memset32(ring->ring, val, chunk2);
+
+       wptr += count;
+       ring->wptr = wptr & ring->ptr_mask;
+       ring->count_dw -= count;
+}
+
  static inline unsigned int amdgpu_ring_get_dw_distance(struct amdgpu_ring
*ring, u64 start_wptr, u64 end_wptr)
  {
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c index 006f3fd3464a..e461e0236b5f
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
@@ -224,15 +224,14 @@ static void sdma_v2_4_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v2_4_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c index 3fb15032e1ef..5cca7f715c6a
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
@@ -401,15 +401,14 @@ static void sdma_v3_0_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v3_0_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c index dfb0ea709bad..63bdf8d4e8d5
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
@@ -784,15 +784,14 @@ static void sdma_v4_0_page_ring_set_wptr(struct
amdgpu_ring *ring) static void sdma_v4_0_ring_insert_nop(struct amdgpu_ring
*ring, uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c index f2e6abe44a43..145f862cbcc6
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_4_2.c
@@ -350,15 +350,14 @@ static void sdma_v4_4_2_page_ring_set_wptr(struct
amdgpu_ring *ring) static void sdma_v4_4_2_ring_insert_nop(struct
amdgpu_ring *ring, uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c index cb36b38582c5..124bc5768983
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
@@ -407,15 +407,14 @@ static void sdma_v5_0_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v5_0_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c index 2858820bb864..242586ea951a
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
@@ -255,15 +255,14 @@ static void sdma_v5_2_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v5_2_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c index d3504606bee7..ae063ac3bd74
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c
@@ -243,15 +243,14 @@ static void sdma_v6_0_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v6_0_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /*
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c index 1760f03db9e7..fd92830d3324
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v7_0.c
@@ -245,15 +245,14 @@ static void sdma_v7_0_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v7_0_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v7_1.c
b/drivers/gpu/drm/amd/amdgpu/sdma_v7_1.c index b9f11f2f7e5c..c0824c83ace9
100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v7_1.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v7_1.c
@@ -239,15 +239,14 @@ static void sdma_v7_1_ring_set_wptr(struct amdgpu_ring
*ring) static void sdma_v7_1_ring_insert_nop(struct amdgpu_ring *ring,
uint32_t count) {
        struct amdgpu_sdma_instance *sdma =
amdgpu_sdma_get_instance_from_ring(ring); -     const bool burst_nop =
sdma->burst_nop;
-       int i;
+       const u32 nop = ring->funcs->nop;

-       for (i = 0; i < count; i++)
-               if (i == 0 && burst_nop)
-                       amdgpu_ring_write(ring, ring->funcs->nop |
-                               SDMA_PKT_NOP_HEADER_COUNT(count -

1));

-               else
-                       amdgpu_ring_write(ring, ring->funcs->nop);
+       if (sdma->burst_nop) {
+               --count;
+               amdgpu_ring_write(ring, nop |

SDMA_PKT_NOP_HEADER_COUNT(count));

+       }
+
+       amdgpu_ring_fill(ring, nop, count);
  }

  /**





























					Reply via email to