linux-kernel - Re: [PATCH 04/11] media: iris: don't specify min_acc

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Message-ID: <4cvcpvobzlcyaqzy7ewhgc3u5gqawt7pa25dz6jkhuwintbkxp@ffun7t4bot6a>
Date: Mon, 12 Jan 2026 00:43:17 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Bryan O'Donoghue <bod@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Akhil P Oommen <akhilpo@....qualcomm.com>,
        Vikash Garodia <vikash.garodia@....qualcomm.com>,
        Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 04/11] media: iris: don't specify min_acc_length in the
 source code

On Sun, Jan 11, 2026 at 09:06:52PM +0000, Bryan O'Donoghue wrote:
> On 10/01/2026 19:37, Dmitry Baryshkov wrote:
> > The min_acc length can be calculated from the platform UBWC
> > configuration. Use the freshly introduced helper and calculate min_acc
> > length based on the platform UBWC configuration instead of specifying it
> > directly in the source.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> > ---
> >   drivers/media/platform/qcom/iris/iris_hfi_gen2_packet.c | 5 ++++-
> >   drivers/media/platform/qcom/iris/iris_platform_common.h | 1 -
> >   drivers/media/platform/qcom/iris/iris_platform_gen2.c   | 1 -
> >   3 files changed, 4 insertions(+), 3 deletions(-)
> > 

> > @@ -146,7 +149,7 @@ void iris_hfi_gen2_packet_sys_init(struct iris_core *core, struct iris_hfi_heade
> >   				    &payload,
> >   				    sizeof(u32));
> > 
> > -	payload = core->iris_platform_data->ubwc_config->mal_length;
> > +	payload = qcom_ubwc_min_acc_length_64b(ubwc) ? 64 : 32;
> >   	iris_hfi_gen2_create_packet(hdr,
> >   				    HFI_PROP_UBWC_MAL_LENGTH,
> >   				    HFI_HOST_FLAGS_NONE,
> 
> This code is fine but, I still suggest changing the 64b postfix in
> qcom_ubwc_min_acc_length_64b and just having the function return the size
> for the platform as _that_ is the more sustainable way.

See how MAL is handled in the DRM patches. If the UBWC spec is extended
to allow 16 or 128 bytes, the drm/msm driver will need to be changed
anyway to cope with that: driver uses flags to pass the value instead of
passing the value as is.

> 
> Up to you.
> 
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> 
> ---
> bod

-- 
With best wishes
Dmitry