linux-kernel - Re: [PATCH v3 26/26] media: dvb-frontends: tda10048: Make the range of z explicit.

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Date: Fri, 3 May 2024 13:56:44 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, Martin Tuma <martin.tuma@...iteqautomotive.com>, 
	Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Hugues Fruchet <hugues.fruchet@...s.st.com>, Alain Volmat <alain.volmat@...s.st.com>, 
	Maxime Coquelin <mcoquelin.stm32@...il.com>, Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Paul Kocialkowski <paul.kocialkowski@...tlin.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, Thierry Reding <thierry.reding@...il.com>, 
	Jonathan Hunter <jonathanh@...dia.com>, Sowjanya Komatineni <skomatineni@...dia.com>, 
	Luca Ceresoli <luca.ceresoli@...tlin.com>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Hans Verkuil <hverkuil@...all.nl>, 
	Sergey Kozlov <serjk@...up.ru>, Abylay Ospan <aospan@...up.ru>, 
	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>, Dmitry Osipenko <digetx@...il.com>, 
	Benjamin Mugnier <benjamin.mugnier@...s.st.com>, 
	Sylvain Petinot <sylvain.petinot@...s.st.com>, 
	Stanimir Varbanov <stanimir.k.varbanov@...il.com>, Vikash Garodia <quic_vgarodia@...cinc.com>, 
	"Bryan O'Donoghue" <bryan.odonoghue@...aro.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel@...ts.infradead.org, linux-staging@...ts.linux.dev, 
	linux-sunxi@...ts.linux.dev, linux-tegra@...r.kernel.org, 
	linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 26/26] media: dvb-frontends: tda10048: Make the range
 of z explicit.

I am trying to get the DS, but
https://www.nxp.com/acrobat_download/literature/9397/75015931.pdf is a
dead links now.

Anyone have access to the datasheet?

Thanks!

On Fri, 3 May 2024 at 13:55, Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> On Fri, May 03, 2024 at 11:27:58AM +0100, Mauro Carvalho Chehab wrote:
> > Em Mon, 29 Apr 2024 15:05:05 +0000
> > Ricardo Ribalda <ribalda@...omium.org> escreveu:
> >
> > > We do not expect the sample_freq to be over 613MHz.
> > >
> > > Found by cocci:
> > > drivers/media/dvb-frontends/tda10048.c:345:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.
> > >
> > > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > > ---
> > >  drivers/media/dvb-frontends/tda10048.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/dvb-frontends/tda10048.c b/drivers/media/dvb-frontends/tda10048.c
> > > index 3e725cdcc66b..1886f733dbbf 100644
> > > --- a/drivers/media/dvb-frontends/tda10048.c
> > > +++ b/drivers/media/dvb-frontends/tda10048.c
> > > @@ -328,7 +328,8 @@ static int tda10048_set_wref(struct dvb_frontend *fe, u32 sample_freq_hz,
> > >                          u32 bw)
> > >  {
> > >     struct tda10048_state *state = fe->demodulator_priv;
> > > -   u64 t, z;
> > > +   u32 z;
> > > +   u64 t;
> > >
> > >     dprintk(1, "%s()\n", __func__);
> > >
> > > @@ -341,6 +342,7 @@ static int tda10048_set_wref(struct dvb_frontend *fe, u32 sample_freq_hz,
> > >     /* t *= 2147483648 on 32bit platforms */
> > >     t *= (2048 * 1024);
> > >     t *= 1024;
> > > +   /* Sample frequency is under 613MHz */
> >
> > Are you sure about that? Some DVB devices have very high frequency
> > clocks, specially if they're also used for satellite, so I can't
> > be sure by just looking at the driver's code.
> >
> > Also, we had already a bunch of regressions with "fixes" like this
> > that actually broke frontend drivers.
>
> This patch preserves the existing behavior. The sample_freq_hz variable
> is a u32 so, in the original code, z couldn't have been more than
> U32_MAX even though it was declared as a u64.
>
> It's possible that the original code was wrong.  We have seen that in
> other places in this patchset.  Adding a note about the datasheet is
> also a good idea.
>
> regards,
> dan carpenter
>


-- 
Ricardo Ribalda