Thanks Kosta!
On Tue, 7 Jan 2025 at 18:28, Kosta Stefanov <costa.stephanoff@xxxxxxxxx> wrote:
>
> hi Ricardo, according to the datasheet the recommended sampling
> frequency is 55 MHz (BTW, if you look at the definitions in the source
> code and make the calculations that is exactly the sampling frequency
> all currently supported in Linux devices are using as well).
>
> also, I spent few minutes time to make the calculations based on the
> restrains of the PLL build-in tda10048 and in theory the maximum is 69
> MHz. so, if you make next revision of this patch, feel free to update
> the comment accordingly, in short - recommended sampling frequency of
> 55 MHz, theoretical maximum of 69 MHz.
>
> in any case, your assumption is correct and in reality is away less
> than the maximum value you assumed.
I have updated the comments in my local copy. I will resend after a
couple of days in case there are more reviews.
May I ask if you could share the datasheet?
Thanks!
>
> Reviewed-by: Kosta Stefanov <costa.stephanoff@xxxxxxxxx>
>
> --Kosta
>
>
> On Tue, Jan 7, 2025 at 12:54 PM Ricardo Ribalda <ribalda@xxxxxxxxxxxx> wrote:
> >
> > We have not been able to find the relevant datahsheet, but it seems rare
> > that the device will have a sampling frequency over 613MHz.
> >
> > Nonetheless, this patch does not introduce any change in behaviour, it
> > just adds a comment to make explicit the current limit: div by 32 bits.
> >
> > 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 */
> > z = 7 * sample_freq_hz;
> > do_div(t, z);
> > t += 5;
> >
> > --
> > 2.47.1.613.gc27f4b7a9f-goog
> >
> >
--
Ricardo Ribalda
