Re: [PATCH v4] drm/amdgpu: Ensure the DMA engine is deactivated during set ups

[Lang Yu <Lang.Yu@amd.com>]

On 04/29/ , Haohui Mai wrote:
> Thanks for pointing it out. The v5 patch added the code back.
> 
> ~Haohui

But you didn't remove the following codes added in v4.

 	if (adev->firmware.load_type == AMDGPU_FW_LOAD_DIRECT) {
+		sdma_v5_2_ctx_switch_disable_all(adev);
+		sdma_v5_2_halt(adev);
+

sdma_v5_2_halt() has been called in sdma_v5_2_load_microcode().

No need to call these two functions here.

Regards,
Lang

> On Thu, Apr 28, 2022 at 10:05 PM Lang Yu <Lang.Yu@amd.com> wrote:
> >
> > On 04/28/ , Haohui Mai wrote:
> > > If I understand correctly, the original code will disable the HALT bit
> > > of the register mmSDMA0_F32_CNTL twice on other code paths -- one in
> > > the sdma_v5_2_ctx_switch_enable() and the other one in
> > > sdma_v5_2_enable().
> > >
> > > The change ensures that the bit is only disabled once. Just wondering,
> > > which one is the expected behavior?
> > >
> > > ~Haohui
> >
> > The HALT bit of the register mmSDMA0_F32_CNTL is not set/reset in original sdma_v5_2_ctx_switch_enable()
> > (https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fagd5f%2Flinux%2F-%2Fblob%2Famd-staging-drm-next%2Fdrivers%2Fgpu%2Fdrm%2Famd%2Famdgpu%2Fsdma_v5_2.c%23L523&amp;data=05%7C01%7CLang.Yu%40amd.com%7C2df035ef6ad5411215a208da299c0253%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637868047861293833%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=%2FLpd6TUyxSe96rEzbyvV0zXNPZ%2BIokiT8KtGAKea8Co%3D&amp;reserved=0)
> >
> > Regards,
> > Lang
> >
> > > On Thu, Apr 28, 2022 at 6:27 PM Lang Yu <Lang.Yu@amd.com> wrote:
> > > >
> > > > On 04/28/ , ricetons@gmail.com wrote:
> > > > > From: Haohui Mai <ricetons@gmail.com>
> > > > >
> > > > > The patch fully deactivates the DMA engine before setting up the ring
> > > > > buffer to avoid potential data races and crashes.
> > > > >
> > > > > The v4 patch addresses the comments from Lang Yu <Lang.Yu@amd.com>.
> > > > >
> > > > > Signed-off-by: Haohui Mai <ricetons@gmail.com>
> > > > > ---
> > > > >  drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c | 113 ++++++++++++++-----------
> > > > >  1 file changed, 62 insertions(+), 51 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..b000117b77d0 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;
> > > > > @@ -539,61 +542,71 @@ 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;
> > > > >
> > > > > -     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);
> > > > > -             }
> > > > > +     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)
> > > > > +{
> > > > > +     sdma_v5_2_gfx_stop(adev);
> > > > > +     sdma_v5_2_rlc_stop(adev);
> > > > > +}
> > > > > +
> > > > >  /**
> > > > >   * sdma_v5_2_gfx_resume - setup and start the async dma engines
> > > > >   *
> > > > >   * @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 +750,7 @@ 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 +794,7 @@ 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 +866,8 @@ 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);
> > > > > @@ -865,6 +875,9 @@ static int sdma_v5_2_start(struct amdgpu_device *adev)
> > > > >       }
> > > > >
> > > > >       if (adev->firmware.load_type == AMDGPU_FW_LOAD_DIRECT) {
> > > > > +             sdma_v5_2_ctx_switch_disable_all(adev);
> > > > > +             sdma_v5_2_halt(adev);
> > > >
> > > > You don't need call these functions here.
> > > >
> > > > In original code, you can see sdma_v5_2_load_microcode() calls
> > > > sdma_v5_2_enable(adev, false) to halt the engine before load ucode.
> > > >
> > > > What I mean is sdma_v5_2_halt(adev) should have no functional change with
> > > > original sdma_v5_2_enable(adev, false), like this,
> > > >
> > > > static void sdma_v5_2_halt(struct amdgpu_device *adev) {
> > > >         u32 f32_cntl;
> > > >         int i;
> > > >
> > > >         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, 1);
> > > >                         WREG32(sdma_v5_2_get_reg_offset(adev, i, mmSDMA0_F32_CNTL), f32_cntl);
> > > >                 }
> > > >         }
> > > > }
> > > >
> > > > But you remove the codes to set the HLAT bit of register mmSDMA0_F32_CNTL.
> > > >
> > > > Regards,
> > > > Lang
> > > >
> > > > >               r = sdma_v5_2_load_microcode(adev);
> > > > >               if (r)
> > > > >                       return r;
> > > > > @@ -881,12 +894,10 @@ 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 +1351,8 @@ 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
> > > > >