Re: [PATCH v5 2/2] pinctrl: qcom: Add sm8250 lpass lpi pinctrl driver

[Srinivas Kandagatla]

On 02/12/2020 09:56, Srinivas Kandagatla wrote:
> > > +        case PIN_CONFIG_SLEW_RATE:
> > > +            if (arg > LPI_SLEW_RATE_MAX) {
> > > +                dev_err(pctldev->dev, "invalid slew rate %u for pin: 
> > > %d\n",
> > > +                    arg, group);
> > > +                return -EINVAL;
> > > +            }
> > > +
> > > +            slew_offset = g->slew_offset;
> > > +            if (slew_offset == NO_SLEW)
> > > +                break;
> > > +
> > > +            mutex_lock(&pctrl->slew_access_lock);
> > > +            sval = ioread32(pctrl->slew_base + LPI_SLEW_RATE_CTL_REG);
> > > +
> > > +            for (i = 0; i < LPI_SLEW_BITS_SIZE; i++) {
> > > +                assign_bit(slew_offset, &sval, arg & 0x01);
> > > +                slew_offset++;
> > > +                arg = arg >> 1;
> > > +            }
> >
> > Isn't this loop just the same as
> >
> >     FIELD_SET(3 << slew_offset, arg & 3, sval)

None of FIELD_* or replace_bits apis will work here, as the mask passed 
to those macros should be a constant #define. Passing variable to them 
in mask will result in compile error!

mask in this case is retrieved at runtime.

I think we should live with the existing code unless there is a strong 
reason for it to change! Or a better alternative.


--srini


>

> This will not work FIELD_SET will not clear any bits wich are already 
> set! assing_bit will work, but we could do better by adding slew_mask 
> per pin rather than slew_offset which should allow us to use 
> replace_bits straight away.