[libcamera-devel] [PATCH 3/3] ipa: ipu3: af: Remove redundant memcpy

[Laurent Pinchart]

Hi Kieran,

Thank you for the patch.

On Tue, Mar 15, 2022 at 05:53:45PM +0000, Kieran Bingham via libcamera-devel wrote:
> The af statistics can be accessed directly from the mapped buffer.
> Remove the redundant memcpy, and simplify the call to
> afEstimateVariance().
> 
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  src/ipa/ipu3/algorithms/af.cpp | 12 ++++--------
>  src/ipa/ipu3/algorithms/af.h   |  2 +-
>  2 files changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/src/ipa/ipu3/algorithms/af.cpp b/src/ipa/ipu3/algorithms/af.cpp
> index 469762a29937..e10cff968895 100644
> --- a/src/ipa/ipu3/algorithms/af.cpp
> +++ b/src/ipa/ipu3/algorithms/af.cpp
> @@ -336,7 +336,7 @@ void Af::afIgnoreFrameReset()
>   *
>   * \return The variance of the values in the data set \a y_item selected by \a isY1
>   */
> -double Af::afEstimateVariance(y_table_item_t *y_item, uint32_t len,
> +double Af::afEstimateVariance(const y_table_item_t *y_item, uint32_t len,
>  			      bool isY1)

Not a candidate for this patch, but pointer + len immediately makes me
think the Span class should be used instead.

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

>  {
>  	uint32_t z = 0;
> @@ -406,25 +406,21 @@ bool Af::afIsOutOfFocus(IPAContext context)
>   */
>  void Af::process(IPAContext &context, const ipu3_uapi_stats_3a *stats)
>  {
> -	y_table_item_t y_item[IPU3_UAPI_AF_Y_TABLE_MAX_SIZE / sizeof(y_table_item_t)];
> +	const y_table_item_t *y_item = reinterpret_cast<const y_table_item_t *>(&stats->af_raw_buffer.y_table);
>  	uint32_t afRawBufferLen;
>  
>  	/* Evaluate the AF buffer length */
>  	afRawBufferLen = context.configuration.af.afGrid.width *
>  			 context.configuration.af.afGrid.height;
>  
> -	memcpy(y_item, stats->af_raw_buffer.y_table,
> -	       afRawBufferLen * sizeof(y_table_item_t));
> +	ASSERT(afRawBufferLen / sizeof(y_table_item_t) < IPU3_UAPI_AF_Y_TABLE_MAX_SIZE);
>  
>  	/*
>  	 * Calculate the mean and the variance of AF statistics for a given grid.
>  	 * For coarse: y1 are used.
>  	 * For fine: y2 results are used.
>  	 */
> -	if (coarseCompleted_)
> -		currentVariance_ = afEstimateVariance(y_item, afRawBufferLen, false);
> -	else
> -		currentVariance_ = afEstimateVariance(y_item, afRawBufferLen, true);
> +	currentVariance_ = afEstimateVariance(y_item, afRawBufferLen, !coarseCompleted_);
>  
>  	if (!context.frameContext.af.stable) {
>  		afCoarseScan(context);
> diff --git a/src/ipa/ipu3/algorithms/af.h b/src/ipa/ipu3/algorithms/af.h
> index 906f2843dd49..3b5758e868ea 100644
> --- a/src/ipa/ipu3/algorithms/af.h
> +++ b/src/ipa/ipu3/algorithms/af.h
> @@ -41,7 +41,7 @@ private:
>  	void afReset(IPAContext &context);
>  	bool afNeedIgnoreFrame();
>  	void afIgnoreFrameReset();
> -	double afEstimateVariance(y_table_item_t *y_item, uint32_t len,
> +	double afEstimateVariance(const y_table_item_t *y_item, uint32_t len,
>  				  bool isY1);
>  	bool afIsOutOfFocus(IPAContext context);
>  

-- 
Regards,

Laurent Pinchart