drm/amdgpu: simplify padding calculations (v2)

Simplify padding calculations.

v2: Comment update and spacing.

Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/cik_sdma.c b/drivers/gpu/drm/amd/amdgpu/cik_sdma.c
index b79e8ec..580d3f9 100644 (file)
--- 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 45e1428..7d509a4 100644 (file)
--- 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 5f0d246..b6109a9 100644 (file)
--- 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 492bca8..ce0753a 100644 (file)
--- 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));
@@ -1579,7 +1579,7 @@ 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 1243cfe..4c6bf1f 100644 (file)
--- 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));
@@ -1076,10 +1083,10 @@ 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)
 {
@@ -1087,7 +1094,7 @@ 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++] =