[Intel-gfx] [PATCH v2 10/19] drm/i915/dsb: Add support for non-posted DSB registers writes

[Manna, Animesh]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Wednesday, June 7, 2023 12:45 AM
> To: intel-gfx at lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH v2 10/19] drm/i915/dsb: Add support for non-
> posted DSB registers writes
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Writing specific transcoder registers (and as it turns out, the legacy LUT as
> well) via DSB needs a magic sequence to emit non-posted register writes.
> Add a helper for this.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Tried to check in bspec where non-posted write for DSB is required and its advantage but could not locate. Not sure if it is captured in bspec. Would it be possible to add some reference in commit description.

Regards,
Animesh

> ---
>  drivers/gpu/drm/i915/display/intel_dsb.c | 20 ++++++++++++++++++++
> drivers/gpu/drm/i915/display/intel_dsb.h |  3 +++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c
> b/drivers/gpu/drm/i915/display/intel_dsb.c
> index 6be353fdc7fc..73d609507f24 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -261,6 +261,26 @@ void intel_dsb_noop(struct intel_dsb *dsb, int
> count)
>  			       DSB_OPCODE_NOOP << DSB_OPCODE_SHIFT);  }
> 
> +void intel_dsb_nonpost_start(struct intel_dsb *dsb) {
> +	struct intel_crtc *crtc = dsb->crtc;
> +	enum pipe pipe = crtc->pipe;
> +
> +	intel_dsb_reg_write_masked(dsb, DSB_CTRL(pipe, dsb->id),
> +				   DSB_NON_POSTED, DSB_NON_POSTED);
> +	intel_dsb_noop(dsb, 4);
> +}
> +
> +void intel_dsb_nonpost_end(struct intel_dsb *dsb) {
> +	struct intel_crtc *crtc = dsb->crtc;
> +	enum pipe pipe = crtc->pipe;
> +
> +	intel_dsb_reg_write_masked(dsb, DSB_CTRL(pipe, dsb->id),
> +				   DSB_NON_POSTED, 0);
> +	intel_dsb_noop(dsb, 4);
> +}
> +
>  static void intel_dsb_align_tail(struct intel_dsb *dsb)  {
>  	u32 aligned_tail, tail;
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h
> b/drivers/gpu/drm/i915/display/intel_dsb.h
> index 983b0d58ad44..54e9e1dc31ee 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsb.h
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.h
> @@ -22,6 +22,9 @@ void intel_dsb_reg_write(struct intel_dsb *dsb,  void
> intel_dsb_reg_write_masked(struct intel_dsb *dsb,
>  				i915_reg_t reg, u32 mask, u32 val);  void
> intel_dsb_noop(struct intel_dsb *dsb, int count);
> +void intel_dsb_nonpost_start(struct intel_dsb *dsb); void
> +intel_dsb_nonpost_end(struct intel_dsb *dsb);
> +
>  void intel_dsb_commit(struct intel_dsb *dsb,
>  		      bool wait_for_vblank);
>  void intel_dsb_wait(struct intel_dsb *dsb);
> --
> 2.39.3