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

[Laurent Pinchart]

On Fri, Apr 26, 2024 at 05:18:58PM +0900, Paul Elder wrote:
> On Fri, Apr 19, 2024 at 09:42:17PM +0100, Kieran Bingham wrote:
> > 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" ?
> 
> I mean I depend on that too (see above "This was meant to be in the same
> series...") but this specific patch also depends on Dan's agc series.
> 
> Or I could preempt his series :)
> 
> > > 
> > > 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.

Add

	/* The lower 4 bits are fractional and meant to be discarded. */

and get my

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

if you also fix the typo in the commit message.

> > 
> > Anyway.
> > 
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > 
> > >         expMeans_ = { params->ae.exp_mean, context.hw->numAeCells };
> > >  
> > >         /*

-- 
Regards,

Laurent Pinchart