Re: [PATCH] drm/amdgpu: simplify padding calculations (v2) (REPOST)

Christian König <ckoenig.leichtzumerken@xxxxxxxxx> · Tue, 26 Nov 2019 12:54:30 +0100

Am 20.11.19 um 23:29 schrieb Luben Tuikov:
Simplify padding calculations.

v2: Comment update and spacing.

Signed-off-by: Luben Tuikov <luben.tuikov@xxxxxxx>

Reviewed-by: Christian König <christian.koenig@xxxxxxx>

---
  drivers/gpu/drm/amd/amdgpu/cik_sdma.c  |  4 ++--
  drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c |  4 ++--
  drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c |  4 ++--
  drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c |  4 ++--
  drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c | 17 ++++++++++++-----
  5 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/cik_sdma.c b/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
index 82cdb8f57bfd..909c9c0b4233 100644
--- a/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
+++ b/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
@@ -228,7 +228,7 @@ static void cik_sdma_ring_emit_ib(struct amdgpu_ring *ring,
  	u32 extra_bits = vmid & 0xf;
  
  	/* IB packet must end on a 8 DW boundary */
-	cik_sdma_ring_insert_nop(ring, (12 - (lower_32_bits(ring->wptr) & 7)) % 8);
+	cik_sdma_ring_insert_nop(ring, (4 - lower_32_bits(ring->wptr)) & 7);
  
  	amdgpu_ring_write(ring, SDMA_PACKET(SDMA_OPCODE_INDIRECT_BUFFER, 0, extra_bits));
  	amdgpu_ring_write(ring, ib->gpu_addr & 0xffffffe0); /* base must be 32 byte aligned */
@@ -811,7 +811,7 @@ static void cik_sdma_ring_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib)
  	u32 pad_count;
  	int i;
  
-	pad_count = (8 - (ib->length_dw & 0x7)) % 8;
+	pad_count = (-ib->length_dw) & 7;
  	for (i = 0; i < pad_count; i++)
  		if (sdma && sdma->burst_nop && (i == 0))
  			ib->ptr[ib->length_dw++] =
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c b/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
index 89e8c74a40f4..1c49f78b2014 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v2_4.c
@@ -255,7 +255,7 @@ static void sdma_v2_4_ring_emit_ib(struct amdgpu_ring *ring,
  	unsigned vmid = AMDGPU_JOB_GET_VMID(job);
  
  	/* IB packet must end on a 8 DW boundary */
-	sdma_v2_4_ring_insert_nop(ring, (10 - (lower_32_bits(ring->wptr) & 7)) % 8);
+	sdma_v2_4_ring_insert_nop(ring, (2 - lower_32_bits(ring->wptr)) & 7);
  
  	amdgpu_ring_write(ring, SDMA_PKT_HEADER_OP(SDMA_OP_INDIRECT) |
  			  SDMA_PKT_INDIRECT_HEADER_VMID(vmid & 0xf));
@@ -750,7 +750,7 @@ static void sdma_v2_4_ring_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib
  	u32 pad_count;
  	int i;
  
-	pad_count = (8 - (ib->length_dw & 0x7)) % 8;
+	pad_count = (-ib->length_dw) & 7;
  	for (i = 0; i < pad_count; i++)
  		if (sdma && sdma->burst_nop && (i == 0))
  			ib->ptr[ib->length_dw++] =
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
index 011fd12c41fe..db752f2e05f9 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v3_0.c
@@ -429,7 +429,7 @@ static void sdma_v3_0_ring_emit_ib(struct amdgpu_ring *ring,
  	unsigned vmid = AMDGPU_JOB_GET_VMID(job);
  
  	/* IB packet must end on a 8 DW boundary */
-	sdma_v3_0_ring_insert_nop(ring, (10 - (lower_32_bits(ring->wptr) & 7)) % 8);
+	sdma_v3_0_ring_insert_nop(ring, (2 - lower_32_bits(ring->wptr)) & 7);
  
  	amdgpu_ring_write(ring, SDMA_PKT_HEADER_OP(SDMA_OP_INDIRECT) |
  			  SDMA_PKT_INDIRECT_HEADER_VMID(vmid & 0xf));
@@ -1021,7 +1021,7 @@ static void sdma_v3_0_ring_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib
  	u32 pad_count;
  	int i;
  
-	pad_count = (8 - (ib->length_dw & 0x7)) % 8;
+	pad_count = (-ib->length_dw) & 7;
  	for (i = 0; i < pad_count; i++)
  		if (sdma && sdma->burst_nop && (i == 0))
  			ib->ptr[ib->length_dw++] =
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
index d209cbf54e7d..7d8c2ec7df5b 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c
@@ -698,7 +698,7 @@ static void sdma_v4_0_ring_emit_ib(struct amdgpu_ring *ring,
  	unsigned vmid = AMDGPU_JOB_GET_VMID(job);
  
  	/* IB packet must end on a 8 DW boundary */
-	sdma_v4_0_ring_insert_nop(ring, (10 - (lower_32_bits(ring->wptr) & 7)) % 8);
+	sdma_v4_0_ring_insert_nop(ring, (2 - lower_32_bits(ring->wptr)) & 7);
  
  	amdgpu_ring_write(ring, SDMA_PKT_HEADER_OP(SDMA_OP_INDIRECT) |
  			  SDMA_PKT_INDIRECT_HEADER_VMID(vmid & 0xf));
@@ -1580,7 +1580,7 @@ static void sdma_v4_0_ring_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib
  	u32 pad_count;
  	int i;
  
-	pad_count = (8 - (ib->length_dw & 0x7)) % 8;
+	pad_count = (-ib->length_dw) & 7;
  	for (i = 0; i < pad_count; i++)
  		if (sdma && sdma->burst_nop && (i == 0))
  			ib->ptr[ib->length_dw++] =
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
index 64c53eed7fac..51ebb2147ee7 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_0.c
@@ -382,8 +382,15 @@ static void sdma_v5_0_ring_emit_ib(struct amdgpu_ring *ring,
  	unsigned vmid = AMDGPU_JOB_GET_VMID(job);
  	uint64_t csa_mc_addr = amdgpu_sdma_get_csa_mc_addr(ring, vmid);
  
-	/* IB packet must end on a 8 DW boundary */
-	sdma_v5_0_ring_insert_nop(ring, (10 - (lower_32_bits(ring->wptr) & 7)) % 8);
+	/* An IB packet must end on a 8 DW boundary--the next dword
+	 * must be on a 8-dword boundary. Our IB packet below is 6
+	 * dwords long, thus add x number of NOPs, such that, in
+	 * modular arithmetic,
+	 * wptr + 6 + x = 8k, k >= 0, which in C is,
+	 * (wptr + 6 + x) % 8 = 0.
+	 * The expression below, is a solution of x.
+	 */
+	sdma_v5_0_ring_insert_nop(ring, (2 - lower_32_bits(ring->wptr)) & 7);
  
  	amdgpu_ring_write(ring, SDMA_PKT_HEADER_OP(SDMA_OP_INDIRECT) |
  			  SDMA_PKT_INDIRECT_HEADER_VMID(vmid & 0xf));
@@ -1086,10 +1093,10 @@ static void sdma_v5_0_vm_set_pte_pde(struct amdgpu_ib *ib,
  }
  
  /**
- * sdma_v5_0_ring_pad_ib - pad the IB to the required number of dw
- *
+ * sdma_v5_0_ring_pad_ib - pad the IB
   * @ib: indirect buffer to fill with padding
   *
+ * Pad the IB with NOPs to a boundary multiple of 8.
   */
  static void sdma_v5_0_ring_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib)
  {
@@ -1097,7 +1104,7 @@ static void sdma_v5_0_ring_pad_ib(struct amdgpu_ring *ring, struct amdgpu_ib *ib
  	u32 pad_count;
  	int i;
  
-	pad_count = (8 - (ib->length_dw & 0x7)) % 8;
+	pad_count = (-ib->length_dw) & 0x7;
  	for (i = 0; i < pad_count; i++)
  		if (sdma && sdma->burst_nop && (i == 0))
  			ib->ptr[ib->length_dw++] =

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