Re: [PATCH v6 07/10] drm/i915/dsb: function to trigger workload execution of DSB.

["Sharma, Shashank" <shashank.sharma@intel.com>]

On 9/12/2019 12:41 AM, Animesh Manna wrote:
> Batch buffer will be created through dsb-reg-write function which can have
> single/multiple request based on usecase and once the buffer is ready
> commit function will trigger the execution of the batch buffer. All
> the registers will be updated simultaneously.
>
> v1: Initial version.
> v2: Optimized code few places. (Chris)
> v3: USed DRM_ERROR for dsb head/tail programming failure. (Shashank)
>
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Shashank Sharma <shashank.sharma@intel.com>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_dsb.c | 42 ++++++++++++++++++++++++
>   drivers/gpu/drm/i915/display/intel_dsb.h |  1 +
>   drivers/gpu/drm/i915/i915_reg.h          |  2 ++
>   3 files changed, 45 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
> index 2b0ffc0afb74..eea86afb0583 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -212,3 +212,45 @@ void intel_dsb_reg_write(struct intel_dsb *dsb, i915_reg_t reg, u32 val)
>   			       (DSB_BYTE_EN << DSB_BYTE_EN_SHIFT) |
>   			       i915_mmio_reg_offset(reg);
>   }
> +
> +void intel_dsb_commit(struct intel_dsb *dsb)
> +{
> +	struct intel_crtc *crtc = container_of(dsb, typeof(*crtc), dsb);
> +	struct drm_device *dev = crtc->base.dev;
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +	enum pipe pipe = crtc->pipe;
> +	u32 tail;
> +
> +	if (!dsb->free_pos)
> +		return;
> +
> +	if (!intel_dsb_enable_engine(dsb))
> +		goto reset;
> +
> +	if (is_dsb_busy(dsb)) {
> +		DRM_ERROR("HEAD_PTR write failed - dsb engine is busy.\n");
> +		goto reset;
> +	}
> +	I915_WRITE(DSB_HEAD(pipe, dsb->id), i915_ggtt_offset(dsb->vma));
> +
> +	tail = ALIGN(dsb->free_pos * 4, CACHELINE_BYTES);
> +	if (tail > dsb->free_pos * 4)
> +		memset(&dsb->cmd_buf[dsb->free_pos], 0,
> +		       (tail - dsb->free_pos * 4));
> +
> +	if (is_dsb_busy(dsb)) {
> +		DRM_ERROR("TAIL_PTR write failed - dsb engine is busy.\n");
> +		goto reset;
> +	}
> +	DRM_DEBUG_KMS("DSB execution started - head 0x%x, tail 0x%x\n",
> +		      i915_ggtt_offset(dsb->vma), tail);
> +	I915_WRITE(DSB_TAIL(pipe, dsb->id), i915_ggtt_offset(dsb->vma) + tail);
> +	if (wait_for(!is_dsb_busy(dsb), 1)) {
> +		DRM_ERROR("Timed out waiting for DSB workload completion.\n");
> +		goto reset;
> +	}
> +
> +reset:
> +	dsb->free_pos = 0;
> +	intel_dsb_disable_engine(dsb);

I am still not very convince if a commit function should be void, I 
would still want it to return success or failure, so that we would know 
if the last operation was successful or not.

I would wait Jani N to comment here, on what he feels about this.

- Shashank

> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h b/drivers/gpu/drm/i915/display/intel_dsb.h
> index 9b2522f20bfb..7389c8c5b665 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.h
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.h
> @@ -43,5 +43,6 @@ void intel_dsb_put(struct intel_dsb *dsb);
>   void intel_dsb_reg_write(struct intel_dsb *dsb, i915_reg_t reg, u32 val);
>   void intel_dsb_indexed_reg_write(struct intel_dsb *dsb, i915_reg_t reg,
>   				 u32 val);
> +void intel_dsb_commit(struct intel_dsb *dsb);
>   
>   #endif
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 2dbaa49f5c74..c77b5066d8dd 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -11687,6 +11687,8 @@ enum skl_power_gate {
>   #define _DSBSL_INSTANCE_BASE		0x70B00
>   #define DSBSL_INSTANCE(pipe, id)	(_DSBSL_INSTANCE_BASE + \
>   					 (pipe) * 0x1000 + (id) * 100)
> +#define DSB_HEAD(pipe, id)		_MMIO(DSBSL_INSTANCE(pipe, id) + 0x0)
> +#define DSB_TAIL(pipe, id)		_MMIO(DSBSL_INSTANCE(pipe, id) + 0x4)
>   #define DSB_CTRL(pipe, id)		_MMIO(DSBSL_INSTANCE(pipe, id) + 0x8)
>   #define   DSB_ENABLE			(1 << 31)
>   #define   DSB_STATUS			(1 << 0)
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