Re: [PATCH] media: rkisp1: Fix Bayer demosaicing bypass

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Fri, Sep 11, 2026 at 08:35:10PM +0300, Laurent Pinchart wrote:
> On Fri, Sep 11, 2026 at 04:43:32PM +0200, Jacopo Mondi wrote:
> > On Fri, Sep 11, 2026 at 03:27:50PM +0100, Kieran Bingham wrote:
> > > Quoting Jacopo Mondi (2026-09-11 14:56:19)
> > > > The RKISP1_CIF_ISP_DEMOSAIC_BYPASS bit, when set, bypasses the
> > > > demosaicing block on the RkISP1 ISP.
> > > >
> > > > The current implementation however clears the bit when demosaicing
> > > > have to be bypassed and sets it when demosaicing has to be enabled,
> > > > effectively inverting the bypass bit handling logic.
> > >
> > > Ouch.
> > >
> > > > Fix this by setting the bypass bit when disabling the demosaicing block,
> > > > and by clearing it instead when demosaicing has to be performed.
> > > >
> > > > The issue never manifested itself as libcamera hasn't an algorithm

s/hasn't/doesn't have/

I'll fix it when applying.

> > > > to control Bayer demosaicing bypass yet.
> > > >
> > > > Fixes: 6c53a7b68c5d ("media: rkisp1: Implement extensible params support")
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > > > ---
> > > > media: rkisp1: Fix demosaicing bypass
> > > > ---
> > > >  drivers/media/platform/rockchip/rkisp1/rkisp1-params.c | 8 ++++----
> > > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c
> > > > index 042b759eba62..496381962f1b 100644
> > > > --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c
> > > > +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c
> > > > @@ -1854,8 +1854,8 @@ rkisp1_ext_params_bdm(struct rkisp1_params *params,
> > > >         const struct rkisp1_ext_params_bdm_config *bdm = &block->bdm;
> > > >
> > > >         if (bdm->header.flags & RKISP1_EXT_PARAMS_FL_BLOCK_DISABLE) {
> > > > -               rkisp1_param_clear_bits(params, RKISP1_CIF_ISP_DEMOSAIC,
> > > > -                                       RKISP1_CIF_ISP_DEMOSAIC_BYPASS);
> > > > +               rkisp1_param_set_bits(params, RKISP1_CIF_ISP_DEMOSAIC,
> > > > +                                     RKISP1_CIF_ISP_DEMOSAIC_BYPASS);
> > > >                 return;
> > > >         }
> > > >
> > > > @@ -1863,8 +1863,8 @@ rkisp1_ext_params_bdm(struct rkisp1_params *params,
> > > >
> > > >         if ((bdm->header.flags & RKISP1_EXT_PARAMS_FL_BLOCK_ENABLE) &&
> > > >             !(params->enabled_blocks & BIT(bdm->header.type)))
> > > > -               rkisp1_param_set_bits(params, RKISP1_CIF_ISP_DEMOSAIC,
> > > > -                                     RKISP1_CIF_ISP_DEMOSAIC_BYPASS);
> > > > +               rkisp1_param_clear_bits(params, RKISP1_CIF_ISP_DEMOSAIC,
> > > > +                                       RKISP1_CIF_ISP_DEMOSAIC_BYPASS);
> > >
> > > I think this also opens us up to add mono formats as explicitly
> > > supported by the ISP and potentially set the demosaic defaulting to off
> > > in that instance?
> > 
> > mmm, I think userspace is in a better position to decide when to
> > bypass debayer instead of relying on auto-configuration of the ISP ?
> > 
> > I guess we'll discuss this when support for luma-only formats will be
> > added to the driver
> 
> While I understand why auto-configuration is tempting, I've found that
> more often than not it makes the life of both the driver and userspace
> more difficult. Look for instance at the colourspace handling code in
> rkisp1.
> 
> > > Anyway, Looks sane to me in this order.
> > >
> > > Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> > thanks
> > 
> > > >  }
> > > >
> > > >  static void
> > > >
> > > > ---
> > > > base-commit: 27953c044974baf7e24dee3e9342fe0103dea80c
> > > > change-id: 20260911-imx8mp-demosaicing-bypass-bb284d9cca60

-- 
Regards,

Laurent Pinchart