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@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> > ---
> > 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
