Re: [Intel-gfx] [PATCH v3 05/14] drm/i915/gt: Add intel_gt_mcr_multicast_rmw() operation

[Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>]

On 14.10.2022 16:02, Matt Roper wrote:
> There are cases where we wish to read from any non-terminated MCR
> register instance (or the primary instance in the case of GAM ranges),
> clear/set some bits, and then write the value back out to the register
> in a multicast manner.  Adding a "multicast RMW" will avoid the need to
> open-code this.
> 
> v2:
>  - Return a u32 to align with the recent change to intel_uncore_rmw.
> 
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_gt_mcr.c | 28 ++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/gt/intel_gt_mcr.h |  3 +++
>  2 files changed, 31 insertions(+)

Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>

Regards,
Bala
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
> index a2047a68ea7a..4dc360f4e344 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
> @@ -302,6 +302,34 @@ void intel_gt_mcr_multicast_write_fw(struct intel_gt *gt, i915_reg_t reg, u32 va
>  	intel_uncore_write_fw(gt->uncore, reg, value);
>  }
>  
> +/**
> + * intel_gt_mcr_multicast_rmw - Performs a multicast RMW operations
> + * @gt: GT structure
> + * @reg: the MCR register to read and write
> + * @clear: bits to clear during RMW
> + * @set: bits to set during RMW
> + *
> + * Performs a read-modify-write on an MCR register in a multicast manner.
> + * This operation only makes sense on MCR registers where all instances are
> + * expected to have the same value.  The read will target any non-terminated
> + * instance and the write will be applied to all instances.
> + *
> + * This function assumes the caller is already holding any necessary forcewake
> + * domains; use intel_gt_mcr_multicast_rmw() in cases where forcewake should
> + * be obtained automatically.
> + *
> + * Returns the old (unmodified) value read.
> + */
> +u32 intel_gt_mcr_multicast_rmw(struct intel_gt *gt, i915_reg_t reg,
> +			       u32 clear, u32 set)
> +{
> +	u32 val = intel_gt_mcr_read_any(gt, reg);
> +
> +	intel_gt_mcr_multicast_write(gt, reg, (val & ~clear) | set);
> +
> +	return val;
> +}
> +
>  /*
>   * reg_needs_read_steering - determine whether a register read requires
>   *     explicit steering
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_mcr.h b/drivers/gpu/drm/i915/gt/intel_gt_mcr.h
> index 77a8b11c287d..781b267478db 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_mcr.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_mcr.h
> @@ -24,6 +24,9 @@ void intel_gt_mcr_multicast_write(struct intel_gt *gt,
>  void intel_gt_mcr_multicast_write_fw(struct intel_gt *gt,
>  				     i915_reg_t reg, u32 value);
>  
> +u32 intel_gt_mcr_multicast_rmw(struct intel_gt *gt, i915_reg_t reg,
> +			       u32 clear, u32 set);
> +
>  void intel_gt_mcr_get_nonterminated_steering(struct intel_gt *gt,
>  					     i915_reg_t reg,
>  					     u8 *group, u8 *instance);
> -- 
> 2.37.3
>