The only thing that matters is that the IP should be halted before
programming the ring buffers.
What about rephrasing the commit messages to highlight the issue a
little bit better?
On Fri, May 6, 2022 at 12:33 AM Alex Deucher <alexdeucher@xxxxxxxxx> wrote:
>
> On Sat, Apr 30, 2022 at 3:34 AM <ricetons@xxxxxxxxx> wrote:
> >
> > From: Haohui Mai <ricetons@xxxxxxxxx>
> >
> > The patch fully deactivates the DMA engine before setting up the ring
> > buffer to avoid potential data races and crashes.
>
> Does this actually fix an issue you are seeing? I don't think it will
> hurt anything, but I also don't think it's strictly necessary. AFAIK,
> only the HALT bit really matters. So the commit message might be
> somewhat misleading.
>
> Alex
>
> >
> > Signed-off-by: Haohui Mai <ricetons@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c | 109 +++++++++++++++----------
> > 1 file changed, 64 insertions(+), 45 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..1fac9d8e99de 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 +504,21 @@ 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.
> > + * @instance_idx: 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 instance_idx)
> > {
> > u32 f32_cntl, phase_quantum = 0;
> > - int i;
> > +
> > + if (WARN_ON(instance_idx >= adev->sdma.num_instances)) {
> > + return;
> > + }
> >
> > if (amdgpu_sdma_phase_quantum) {
> > unsigned value = amdgpu_sdma_phase_quantum;
> > @@ -539,50 +542,68 @@ 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;
> > - }
> > -
> > - 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, enable ? 1 : 0);
> > - WREG32(sdma_v5_2_get_reg_offset(adev, i, mmSDMA0_CNTL), f32_cntl);
> > - }
> > + WREG32_SOC15_IP(GC,
> > + sdma_v5_2_get_reg_offset(adev, instance_idx, mmSDMA0_PHASE0_QUANTUM),
> > + phase_quantum);
> > + WREG32_SOC15_IP(GC,
> > + sdma_v5_2_get_reg_offset(adev, instance_idx, mmSDMA0_PHASE1_QUANTUM),
> > + phase_quantum);
> > + WREG32_SOC15_IP(GC,
> > + sdma_v5_2_get_reg_offset(adev, instance_idx, mmSDMA0_PHASE2_QUANTUM),
> > + phase_quantum);
> > }
> >
> > + if (!amdgpu_sriov_vf(adev)) {
> > + f32_cntl = RREG32(sdma_v5_2_get_reg_offset(adev, instance_idx, mmSDMA0_CNTL));
> > + f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_CNTL,
> > + AUTO_CTXSW_ENABLE, 1);
> > + WREG32(sdma_v5_2_get_reg_offset(adev, instance_idx, mmSDMA0_CNTL), f32_cntl);
> > + }
> > }
> >
> > /**
> > - * sdma_v5_2_enable - stop the async dma engines
> > + * sdma_v5_2_ctx_switch_disable_all - stop the async dma engines context switch
> > *
> > * @adev: amdgpu_device pointer
> > - * @enable: enable/disable the DMA MEs.
> > *
> > - * Halt or unhalt the async dma engines.
> > + * Halt the async dma engines context switch.
> > */
> > -static void sdma_v5_2_enable(struct amdgpu_device *adev, bool enable)
> > +static void sdma_v5_2_ctx_switch_disable_all(struct amdgpu_device *adev)
> > {
> > u32 f32_cntl;
> > int i;
> >
> > - if (!enable) {
> > - sdma_v5_2_gfx_stop(adev);
> > - sdma_v5_2_rlc_stop(adev);
> > + 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);
> > }
> > +}
> > +
> > +/**
> > + * sdma_v5_2_halt - stop the async dma engines
> > + *
> > + * @adev: amdgpu_device pointer
> > + *
> > + * Halt the async dma engines.
> > + */
> > +static void sdma_v5_2_halt(struct amdgpu_device *adev)
> > +{
> > + int i;
> > + u32 f32_cntl;
> > +
> > + 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);
> > + f32_cntl = REG_SET_FIELD(f32_cntl, SDMA0_F32_CNTL, HALT, 1);
> > WREG32(sdma_v5_2_get_reg_offset(adev, i, mmSDMA0_F32_CNTL), f32_cntl);
> > }
> > }
> > @@ -594,6 +615,9 @@ 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 +761,7 @@ 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) {
> > @@ -784,7 +805,7 @@ static int sdma_v5_2_load_microcode(struct amdgpu_device *adev)
> > int i, j;
> >
> > /* halt the MEs */
> > - sdma_v5_2_enable(adev, false);
> > + sdma_v5_2_halt(adev);
> >
> > for (i = 0; i < adev->sdma.num_instances; i++) {
> > if (!adev->sdma.instance[i].fw)
> > @@ -856,8 +877,8 @@ 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_enable(adev, false);
> > + sdma_v5_2_ctx_switch_disable_all(adev);
> > + sdma_v5_2_halt(adev);
> >
> > /* set RB registers */
> > r = sdma_v5_2_gfx_resume(adev);
> > @@ -881,12 +902,10 @@ 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);
> > @@ -1340,8 +1359,8 @@ 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_enable(adev, false);
> > + sdma_v5_2_ctx_switch_disable_all(adev);
> > + sdma_v5_2_halt(adev);
> >
> > return 0;
> > }
> > --
> > 2.25.1
> >
