linux-kernel - Re: [PATCH v1 1/1] media: rkisp1: Fix filter mode register configuration

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Message-ID: <176761256763.3192372.8001486757502337420@ping.linuxembedded.co.uk>
Date: Mon, 05 Jan 2026 11:29:27 +0000
From: Kieran Bingham <kieran.bingham@...asonboard.com>
To: Rui Wang <rui.wang@...asonboard.com>, Stefan Klug <stefan.klug@...asonboard.com>, dafna@...tmail.com, heiko@...ech.de, laurent.pinchart@...asonboard.com, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org, mchehab@...nel.org
Cc: libcamera-devel@...ts.libcamera.org, Rui Wang <rui.wang@...asonboard.com>
Subject: Re: [PATCH v1 1/1] media: rkisp1: Fix filter mode register configuration

Quoting Stefan Klug (2025-12-02 06:42:36)
> Hi Rui,
> 
> Thank you for the patch.
> 
> Quoting Rui Wang (2025-12-02 02:50:25)
> > The rkisp1_flt_config() function performs an initial direct write to
> > RKISP1_CIF_ISP_FILT_MODE without including the RKISP1_CIF_ISP_FLT_ENA
> > bit, which clears the filter enable bit in the hardware.
> 
> That sentence is a bit hard for me to understand. Maybe:
> 
> "The rkisp1_flt_config() function overwrites RKISP1_CIF_ISP_FILT_MODE
> without preserving the RKISP1_CIF_ISP_FLT_ENA bit thereby unconditionally
> disabling the hardware block on reconfiguration.


Stefan's proposal sounds good here.


Reviewed-by: Kieran Bingham <kieran.bingham@...asonboard.com>

> 
> But as I'm no native speaker you could maybe wait for feedback from a
> native speaker.
> 
> Functionality wise the change is correct.
> 
> Reviewed-by: Stefan Klug <stefan.klug@...asonboard.com>
> 
> Best regards,
> Stefan
> 
> > 
> > The subsequent read/modify/write sequence then reads back the register
> > with the enable bit already cleared and cannot restore it, resulting in
> > the filter being inadvertently disabled.
> > 
> > Remove the redundant direct write. The read/modify/write sequence alone
> > correctly preserves the existing enable bit state while updating the
> > DNR mode and filter configuration bits.
> > 
> > Signed-off-by: Rui Wang <rui.wang@...asonboard.com>
> > ---
> >  drivers/media/platform/rockchip/rkisp1/rkisp1-params.c | 6 ------
> >  1 file changed, 6 deletions(-)
> > 
> > diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c
> > index c9f88635224c..6442436a5e42 100644
> > --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c
> > +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-params.c
> > @@ -411,12 +411,6 @@ static void rkisp1_flt_config(struct rkisp1_params *params,
> >         rkisp1_write(params->rkisp1, RKISP1_CIF_ISP_FILT_LUM_WEIGHT,
> >                      arg->lum_weight);
> >  
> > -       rkisp1_write(params->rkisp1, RKISP1_CIF_ISP_FILT_MODE,
> > -                    (arg->mode ? RKISP1_CIF_ISP_FLT_MODE_DNR : 0) |
> > -                    RKISP1_CIF_ISP_FLT_CHROMA_V_MODE(arg->chr_v_mode) |
> > -                    RKISP1_CIF_ISP_FLT_CHROMA_H_MODE(arg->chr_h_mode) |
> > -                    RKISP1_CIF_ISP_FLT_GREEN_STAGE1(arg->grn_stage1));
> > -
> >         /* avoid to override the old enable value */
> >         filt_mode = rkisp1_read(params->rkisp1, RKISP1_CIF_ISP_FILT_MODE);
> >         filt_mode &= RKISP1_CIF_ISP_FLT_ENA;
> > -- 
> > 2.43.0
> >