From: Haohui Mai <ricet...@gmail.com>

The patch fully deactivates the DMA engine before setting up the ring
buffer to avoid potential data races and crashes.

Signed-off-by: Haohui Mai <ricet...@gmail.com>
---
 drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c | 88 +++++++++++++-------------
 1 file changed, 45 insertions(+), 43 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c 
b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
index 013d2dec81d0..61d58e515fe7 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
@@ -459,7 +459,6 @@ static void sdma_v5_2_ring_emit_fence(struct amdgpu_ring 
*ring, u64 addr, u64 se
        }
 }
 
-
 /**
  * sdma_v5_2_gfx_stop - stop the gfx async dma engines
  *
@@ -505,17 +504,18 @@ static void sdma_v5_2_rlc_stop(struct amdgpu_device *adev)
 }
 
 /**
- * sdma_v5_2_ctx_switch_enable - stop the async dma engines context switch
+ * sdma_v5_2_ctx_switch_enable_for_instance - start the async dma engines 
context switch for an instance
  *
  * @adev: amdgpu_device pointer
- * @enable: enable/disable the DMA MEs context switch.
+ * @i: the index of the SDMA instance
  *
- * Halt or unhalt the async dma engines context switch.
+ * Unhalt the async dma engines context switch.
  */
-static void sdma_v5_2_ctx_switch_enable(struct amdgpu_device *adev, bool 
enable)
+static void sdma_v5_2_ctx_switch_enable_for_instance(struct amdgpu_device 
*adev, int i)
 {
        u32 f32_cntl, phase_quantum = 0;
-       int i;
+
+       BUG_ON(i >= adev->sdma.num_instances);
 
        if (amdgpu_sdma_phase_quantum) {
                unsigned value = amdgpu_sdma_phase_quantum;
@@ -539,26 +539,44 @@ static void sdma_v5_2_ctx_switch_enable(struct 
amdgpu_device *adev, bool enable)
                phase_quantum =
                        value << SDMA0_PHASE0_QUANTUM__VALUE__SHIFT |
                        unit  << SDMA0_PHASE0_QUANTUM__UNIT__SHIFT;
+
+               WREG32_SOC15_IP(GC, sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_PHASE0_QUANTUM),
+                      phase_quantum);
+               WREG32_SOC15_IP(GC, sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_PHASE1_QUANTUM),
+                      phase_quantum);
+               WREG32_SOC15_IP(GC, sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_PHASE2_QUANTUM),
+                      phase_quantum);
        }
 
-       for (i = 0; i < adev->sdma.num_instances; i++) {
-               if (enable && amdgpu_sdma_phase_quantum) {
-                       WREG32_SOC15_IP(GC, sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_PHASE0_QUANTUM),
-                              phase_quantum);
-                       WREG32_SOC15_IP(GC, sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_PHASE1_QUANTUM),
-                              phase_quantum);
-                       WREG32_SOC15_IP(GC, sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_PHASE2_QUANTUM),
-                              phase_quantum);
-               }
+       if (!amdgpu_sriov_vf(adev)) {
+               f32_cntl = RREG32(sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_CNTL));
+               f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_CNTL,
+                               AUTO_CTXSW_ENABLE, 1);
+               WREG32(sdma_v5_2_get_reg_offset(adev, i, mmSDMA0_CNTL), 
f32_cntl);
+       }
+}
 
-               if (!amdgpu_sriov_vf(adev)) {
-                       f32_cntl = RREG32(sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_CNTL));
-                       f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_CNTL,
-                                       AUTO_CTXSW_ENABLE, enable ? 1 : 0);
-                       WREG32(sdma_v5_2_get_reg_offset(adev, i, mmSDMA0_CNTL), 
f32_cntl);
-               }
+/**
+ * sdma_v5_2_ctx_switch_disable_all - stop the async dma engines context switch
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * Halt the async dma engines context switch.
+ */
+static void sdma_v5_2_ctx_switch_disable_all(struct amdgpu_device *adev)
+{
+       u32 f32_cntl;
+       int i;
+       if (amdgpu_sriov_vf(adev)) {
+               return;
        }
 
+       for (i = 0; i < adev->sdma.num_instances; i++) {
+               f32_cntl = RREG32(sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_CNTL));
+               f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_CNTL,
+                               AUTO_CTXSW_ENABLE, 0);
+               WREG32(sdma_v5_2_get_reg_offset(adev, i, mmSDMA0_CNTL), 
f32_cntl);
+       }
 }
 
 /**
@@ -571,21 +589,10 @@ static void sdma_v5_2_ctx_switch_enable(struct 
amdgpu_device *adev, bool enable)
  */
 static void sdma_v5_2_enable(struct amdgpu_device *adev, bool enable)
 {
-       u32 f32_cntl;
-       int i;
-
        if (!enable) {
                sdma_v5_2_gfx_stop(adev);
                sdma_v5_2_rlc_stop(adev);
        }
-
-       if (!amdgpu_sriov_vf(adev)) {
-               for (i = 0; i < adev->sdma.num_instances; i++) {
-                       f32_cntl = RREG32(sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_F32_CNTL));
-                       f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_F32_CNTL, 
HALT, enable ? 0 : 1);
-                       WREG32(sdma_v5_2_get_reg_offset(adev, i, 
mmSDMA0_F32_CNTL), f32_cntl);
-               }
-       }
 }
 
 /**
@@ -594,6 +601,8 @@ static void sdma_v5_2_enable(struct amdgpu_device *adev, 
bool enable)
  * @adev: amdgpu_device pointer
  *
  * Set up the gfx DMA ring buffers and enable them.
+ * It assumes that the dma engine is stopped for each instance. The function 
enables the engine and preemptions sequentially for each instance.
+ *
  * Returns 0 for success, error for failure.
  */
 static int sdma_v5_2_gfx_resume(struct amdgpu_device *adev)
@@ -737,10 +746,7 @@ static int sdma_v5_2_gfx_resume(struct amdgpu_device *adev)
 
                ring->sched.ready = true;
 
-               if (amdgpu_sriov_vf(adev)) { /* bare-metal sequence doesn't 
need below to lines */
-                       sdma_v5_2_ctx_switch_enable(adev, true);
-                       sdma_v5_2_enable(adev, true);
-               }
+               sdma_v5_2_ctx_switch_enable_for_instance(adev, i);
 
                r = amdgpu_ring_test_ring(ring);
                if (r) {
@@ -856,7 +862,7 @@ static int sdma_v5_2_start(struct amdgpu_device *adev)
        int r = 0;
 
        if (amdgpu_sriov_vf(adev)) {
-               sdma_v5_2_ctx_switch_enable(adev, false);
+               sdma_v5_2_ctx_switch_disable_all(adev);
                sdma_v5_2_enable(adev, false);
 
                /* set RB registers */
@@ -881,12 +887,8 @@ static int sdma_v5_2_start(struct amdgpu_device *adev)
                amdgpu_gfx_off_ctrl(adev, false);
 
        sdma_v5_2_soft_reset(adev);
-       /* unhalt the MEs */
-       sdma_v5_2_enable(adev, true);
-       /* enable sdma ring preemption */
-       sdma_v5_2_ctx_switch_enable(adev, true);
 
-       /* start the gfx rings and rlc compute queues */
+       /* Soft reset supposes to disable the dma engine and preemption. Now 
start the gfx rings and rlc compute queues */
        r = sdma_v5_2_gfx_resume(adev);
        if (adev->in_s0ix)
                amdgpu_gfx_off_ctrl(adev, true);
@@ -1340,7 +1342,7 @@ static int sdma_v5_2_hw_fini(void *handle)
        if (amdgpu_sriov_vf(adev))
                return 0;
 
-       sdma_v5_2_ctx_switch_enable(adev, false);
+       sdma_v5_2_ctx_switch_disable_all(adev);
        sdma_v5_2_enable(adev, false);
 
        return 0;
-- 
2.25.1

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