[U-Boot] [PATCH v6 15/20] tegra: fdt: Add function to return peripheral/clock ID

[Stephen Warren]

Simon Glass wrote at Tuesday, February 28, 2012 11:44 AM:
> On Tue, Feb 28, 2012 at 10:37 AM, Stephen Warren <swarren at nvidia.com> wrote:
> > Simon Glass wrote at Tuesday, February 28, 2012 10:46 AM:
> >> On Mon, Feb 27, 2012 at 3:41 PM, Stephen Warren <swarren at nvidia.com> wrote:
> >> > On 02/27/2012 01:52 PM, Simon Glass wrote:
> >> >> A common requirement is to find the clock ID for a peripheral. This is the
> >> >> second cell of the 'clocks' property (the first being the phandle itself).
> >> >
> >> >> +int clock_decode_periph_id(const void *blob, int node)
> >> >
> >> >> +     valid = clock_periph_id_isvalid(id);
> >> >
> >> > clock_periph_id_isvalid() is not the correct function to use here; the
> >> > code should be checking for invalid IDs in the CAR binding, not invalid
> >> > IDs in the HW periph ID definition. They're different.
> >> >
> >> > Just to be explicit, the function you need here would be:
> >> >
> >> > int clkid_to_periphid(int clkid)
> >> > {
> >> >    if (clk_id > 95)
> >> >        return -1;
> >> >    switch (clk_id) {
> >> >    case 1:
> >> >    case 2:
> >> >    case 7:
> >> >    case 10:
> >> >    case 20:
> >> >    case 30:
> >> >    case 35:
> >> >    case 49:
> >> >    case 56:
> >> >    case 74:
> >> >    case 77:
> >> >    case 78:
> >> >    case 79:
> >> >    case 80:
> >> >    case 81:
> >> >    case 82:
> >> >    case 83:
> >> >    case 91:
> >> >    case 95:
> >> >        return -1;
> >> >    default:
> >> >        return clkid;
> >> >    }
> >> > }
> >>
> >> Ick.
> >>
> >> Why is 7 in there,
> >
> > 7 affects both the UART2 and VFIR clocks/blocks.
> >
> >> and did you miss 76?
> >
> > No, that's the undocumented "la" clock.
> >
> >> Also U-Boot only goes up to 88
> >> at present so should I change the first test to match?
> >
> > No, clocks 89, 90, 92, 93, and 94 are defined in the binding, which
> > matches the CLK_OUT_ENB registers in the Tegra CAR HW (albeit not the
> > CLK_RST registers, since there are some differences between the two).
> 
> For both of your comments, since they aren't used in U-Boot, wouldn't
> it be more correct to flag these as errors also? We would have to
> update at least the clock.h header to support them.

It's probably more correct to update the periph_id enum to define all
the valid values, but either way is fine.

-- 
nvpublic