On Sun, Sep 13, 2020 at 09:42:33PM +0200, Drew Fustini wrote:
> On Tue, Sep 08, 2020 at 04:52:58PM -0700, Trent Piepho wrote:
> > On Tuesday, June 30, 2020 6:33:19 PM PDT Drew Fustini wrote:
> > > If "pinctrl-single,pins" has 3 arguments (offset, conf, mux), then
> > > pcs_parse_one_pinctrl_entry() does an OR operation on conf and mux to
> > > get the value to store in the register.
> >
> >
> > > - vals[found].val = pinctrl_spec.args[1];
> > > +
> > > + switch (pinctrl_spec.args_count) {
> > > + case 2:
> > > + vals[found].val = pinctrl_spec.args[1];
> > > + break;
> > > + case 3:
> > > + vals[found].val = (pinctrl_spec.args[1] |
> > pinctrl_spec.args[2]);
> > > + break;
> > > + }
> > >
> > > dev_dbg(pcs->dev, "%pOFn index: 0x%x value: 0x%x\n",
> > > pinctrl_spec.np, offset,
> > pinctrl_spec.args[1]);
> >
> > If #pinctrl-cells value is greater than 2, nothing will set vals[found].val to
> > anything other than zero (from when it's calloc'ed) and the pinctrl will
> > silently be programmed to zero.
>
> If #pinctrl-cells is 3, then it will be:
>
> vals[found].val = (pinctrl_spec.args[1] | pinctrl_spec.args[2]);
>
> Do you mean if #pinctrl-cells is great than 3 then it will just have a
> default value of zero?
>
> That does appear to be the case and is probably not the behavior we
> want. Thank you for pointing this out. Earlier, there is a check to
> make sure there are at least 2 arguments:
>
> if (pinctrl_spec.args_count < 2) {
> dev_err(pcs->dev, "invalid args_count for spec: %i\n",
> pinctrl_spec.args_count);
> break;
> }
>
> I'll submit a patch where the upper bound is also checked:
>
> if (pinctrl_spec.args_count < 2 || pinctrl_spec.args_count > 3) {
> dev_err(pcs->dev, "invalid args_count for spec: %i\n",
> pinctrl_spec.args_count);
> break;
> }
>
I was mistaken when I wrote the above. I was using the term
#pinctrl-cells when I should have been writing pinctrl_spec.args_count.
pinctrl_spec.args_count is 2 when #pictrl-cells is 1.
pinctrl_spec.args_count is 3 when #pictrl-cells is 2.
I have submitted patches [1][2] with fixes for the bounds check and the
dev_dbg().
> > The debug printout was not change to print vals[found].val, so it will
> > continue to print the value of the 2nd cell.
>
> Thank you for pointing this out. Yes, this is an oversight and I will
> submit a patch.
>
> > The result is that a #pinctrl-cells of 3 will produce no warning or error,
> > program the pinctrl to zero, whilst at the same time emit debug log messages
> > that it is programming the expected values.
> >
> > The device tree documentation still states that #pinctrl-cells must be 1 when
> > using pinctrl-single,pins. This new special case of ORing two values is not
> > documented.
>
> This is a good point, too. I will make a patch to update the
> documentation.
>
>
> -Drew
[1] https://lore.kernel.org/linux-omap/20200913231557.2063071-1-drew@xxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-omap/20200913230306.2061645-1-drew@xxxxxxxxxxxxxxx/
