Re: [PATCH net-next v11 13/14] dpll: zl3073x: Add support to get/set frequency on input pins

[Ivan Vecera]

On 19. 06. 25 2:15 odp., Vadim Fedorenko wrote:
> On 19/06/2025 12:15, Paolo Abeni wrote:
> > On 6/16/25 10:14 PM, Ivan Vecera wrote:
> > > +/**
> > > + * zl3073x_dpll_input_ref_frequency_get - get input reference frequency
> > > + * @zldpll: pointer to zl3073x_dpll
> > > + * @ref_id: reference id
> > > + * @frequency: pointer to variable to store frequency
> > > + *
> > > + * Reads frequency of given input reference.
> > > + *
> > > + * Return: 0 on success, <0 on error
> > > + */
> > > +static int
> > > +zl3073x_dpll_input_ref_frequency_get(struct zl3073x_dpll *zldpll, u8 
> > > ref_id,
> > > +                     u32 *frequency)
> > > +{
> > > +    struct zl3073x_dev *zldev = zldpll->dev;
> > > +    u16 base, mult, num, denom;
> > > +    int rc;
> > > +
> > > +    guard(mutex)(&zldev->multiop_lock);
> > > +
> > > +    /* Read reference configuration */
> > > +    rc = zl3073x_mb_op(zldev, ZL_REG_REF_MB_SEM, ZL_REF_MB_SEM_RD,
> > > +               ZL_REG_REF_MB_MASK, BIT(ref_id));
> > > +    if (rc)
> > > +        return rc;
> > > +
> > > +    /* Read registers to compute resulting frequency */
> > > +    rc = zl3073x_read_u16(zldev, ZL_REG_REF_FREQ_BASE, &base);
> > > +    if (rc)
> > > +        return rc;
> > > +    rc = zl3073x_read_u16(zldev, ZL_REG_REF_FREQ_MULT, &mult);
> > > +    if (rc)
> > > +        return rc;
> > > +    rc = zl3073x_read_u16(zldev, ZL_REG_REF_RATIO_M, &num);
> > > +    if (rc)
> > > +        return rc;
> > > +    rc = zl3073x_read_u16(zldev, ZL_REG_REF_RATIO_N, &denom);
> > > +    if (rc)
> > > +        return rc;
> > > +
> > > +    /* Sanity check that HW has not returned zero denominator */
> > > +    if (!denom) {
> > > +        dev_err(zldev->dev,
> > > +            "Zero divisor for ref %u frequency got from device\n",
> > > +            ref_id);
> > > +        return -EINVAL;
> > > +    }
> > > +
> > > +    /* Compute the frequency */
> > > +    *frequency = base * mult * num / denom;
> >
> > As base, mult, num and denom are u16, the above looks like integer
> > overflow prone.
> >
> > I think you should explicitly cast to u64, and possibly use a u64 
> > frequency.
>
> I might be a good idea to use mul_u64_u32_div together with mul_u32_u32?
> These macroses will take care of overflow on 32bit platforms as well.

Will fix

Thanks for tip.

Ivan

> > /P