On Mon, Dec 05, 2011 at 02:15:56PM -0700, Paul Walmsley wrote:
> The types associated with clock rates in the clock interface
> (include/linux/clk.h) are inconsistent, and we should fix this.
Rubbish. They're different with good reason. Rates are primerily
unsigned quantities - and should be treated as such.
The exception is clk_round_rate() which returns the rate, but also
_may_ return an error. Therefore, its return type has to be signed.
> We could fix the immediate problem by changing the prototype of
> clk_round_rate() to pass the rounded rate back to the caller via a pointer
> in one of the arguments, and return an error code (if any) via the return
> value:
>
> int clk_round_rate(struct clk *clk, unsigned long rate, unsigned long
> *rounded_rate);
Yes that might have been a better solution.
> But I'd propose that we instead increase the size of struct clk.rate to be
> s64:
>
> s64 clk_round_rate(struct clk *clk, s64 desired_rate);
> int clk_set_rate(struct clk *clk, s64 rate);
> s64 clk_get_rate(struct clk *clk);
>
> struct clk {
> ...
> s64 rate;
> ...
> };
>
> That way the clock framework can accommodate current clock rates, as well
> as any conceivable future clock rate. (Some production CPUs are already
> running at clock rates greater than 4 GiHZ[1]. RF devices with 4 GiHz+
> clock rates are also common, such as 802.11a devices running in the 5.8
> GHz band, and drivers for those may eventually wish to use the clock
> framework.)
Yuck. You are aware that 64-bit math on 32-bit CPUs sucks? So burdening
_everything_ with 64-bit rate quantities is absurd. As for making then
64-bit signed quantities, that's asking for horrid code from gcc for the
majority of cases.
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