linux-kernel - Re: [PATCH 5/7] drm/msm/a5xx: Fix VPC protect value in gpu

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Message-ID: <CAK7fi1Z8uVRE+HRUSTz8bdDS5hYXaH8=D8KDUz+7mGs-H-TGpw@mail.gmail.com>
Date:   Mon, 28 Sep 2020 22:29:00 +0200
From:   AngeloGioacchino Del Regno <kholk11@...il.com>
To:     AngeloGioacchino Del Regno <kholk11@...il.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Dave Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, konradybcio@...il.com,
        marijns95@...il.com, martin.botka1@...il.com,
        MSM <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        phone-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] drm/msm/a5xx: Fix VPC protect value in gpu_write()

Il giorno lun 28 set 2020 alle ore 18:16 Jordan Crouse
<jcrouse@...eaurora.org> ha scritto:
>
> On Sat, Sep 26, 2020 at 02:51:44PM +0200, kholk11@...il.com wrote:
> > From: Konrad Dybcio <konradybcio@...il.com>
> >
> > The upstream API for some reason uses logbase2 instead of
> > just passing the argument as-is, whereas downstream CAF
> > kernel does the latter.
> >
> > Hence, a mistake has been made when porting:
> > 4 is the value that's supposed to be passed, but
> > log2(4) = 2. Changing the value to 16 (= 2^4) fixes
> > the issue.
>
> FWIW I think downstream is wrong. Its a lot more intuitive to pass the number of
> registers that should be protected than to force a human to do math.
>
> Jordan
>
Uhm, actually, it's upstream the one forcing to do math... :P
In any case, downstream you have some calls with an explicit log2 and
some others with the "real" number of registers.

Hardware magic register layouts, maybe.... :)))

-- Angelo

> > Signed-off-by: Konrad Dybcio <konradybcio@...il.com>
> > Signed-off-by: AngeloGioacchino Del Regno <kholk11@...il.com>
> > ---
> >  drivers/gpu/drm/msm/adreno/a5xx_gpu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> > index 00df5de3c8e3..b2670af638a3 100644
> > --- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> > @@ -789,7 +789,7 @@ static int a5xx_hw_init(struct msm_gpu *gpu)
> >
> >       /* VPC */
> >       gpu_write(gpu, REG_A5XX_CP_PROTECT(14), ADRENO_PROTECT_RW(0xE68, 8));
> > -     gpu_write(gpu, REG_A5XX_CP_PROTECT(15), ADRENO_PROTECT_RW(0xE70, 4));
> > +     gpu_write(gpu, REG_A5XX_CP_PROTECT(15), ADRENO_PROTECT_RW(0xE70, 16));
> >
> >       /* UCHE */
> >       gpu_write(gpu, REG_A5XX_CP_PROTECT(16), ADRENO_PROTECT_RW(0xE80, 16));
> > --
> > 2.28.0
> >
>
> --
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