[PATCH v2] ipa: rkisp1: agc: Fix histogram construction

[Kieran Bingham]

Quoting Paul Elder (2024-04-19 06:58:49)
> This histogram reported by the rkisp1 hardware is 20 bits, where the
> upper 16 bits are meaningful integer data and the lower 4 bits are
> fractional and meant to be discarded. Remove thse 4 bits when
> construction the histogram.
> 
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> 
> ---
> This was meant to be in the same series as "[PATCH v2] ipa: libipa:
> histogram: Add transform parameter to constructor"
> 
> This depends on v2 of "Centralise Agc into libipa".

I assume you mean

"[PATCH v2] ipa: libipa: histogram: Add transform parameter to constructor" ?

> 
> Changes in v2:
> - use a lambda function instead of the rshift parameter
> ---
>  src/ipa/rkisp1/algorithms/agc.cpp | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
> index 27b6f2c1..26526f5e 100644
> --- a/src/ipa/rkisp1/algorithms/agc.cpp
> +++ b/src/ipa/rkisp1/algorithms/agc.cpp
> @@ -278,7 +278,8 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
>         const rkisp1_cif_isp_stat *params = &stats->params;
>         ASSERT(stats->meas_type & RKISP1_CIF_ISP_STAT_AUTOEXP);
>  
> -       Histogram hist({ params->hist.hist_bins, context.hw->numHistogramBins });
> +       Histogram hist({ params->hist.hist_bins, context.hw->numHistogramBins },
> +                      [](uint32_t x) { return x >> 4; });

It's a clean fix and more generalised and still optimised so works for
me.

I would have thought a comment above would be beneficial to explain why
we're shifting all the values right 4 here though.

Anyway.

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

>         expMeans_ = { params->ae.exp_mean, context.hw->numAeCells };
>  
>         /*
> -- 
> 2.39.2
>