On Sat, Jan 08, 2022 at 07:47:32PM +0200, Andy Shevchenko wrote: > On Sat, Jan 8, 2022 at 3:20 PM Gabriel L. Somlo <gsomlo@xxxxxxxxx> wrote: > > On Sat, Jan 08, 2022 at 01:26:08PM +0200, Andy Shevchenko wrote: > > > On Sat, Jan 8, 2022 at 3:57 AM Gabriel L. Somlo <gsomlo@xxxxxxxxx> wrote: > > > > On Sat, Jan 08, 2022 at 01:54:07AM +0200, Andy Shevchenko wrote: > > > > > On Saturday, January 8, 2022, Gabriel Somlo <gsomlo@xxxxxxxxx> wrote: > > ... > > > > > > + u32 div; > > > > > + > > > > > + div = freq ? host->ref_clk / freq : 256U; > > > > > > > > > > + div = roundup_pow_of_two(div); > > > > > + div = clamp(div, 2U, 256U); > > > > > > > > > > Logically seems to me that you may join these two together, because clamped > > > > > range is power-of-2 one. > > > > > > > > `div` needs to be a power-of-2 when written to the LITEX_PHY_CLOCKERDIV > > > > register (below). And clamp() will just enforce a min/max range, so if > > > > (div = ref_clk / freq) ends up e.g., 5, I need both roundup_pow_of_two() > > > > to bump it to 8, and clamp() to enforce that it's between 2 and 256. > > > > > > > > Unless you mean I should simply write it like: > > > > > > > > div = clamp(roundup_pow_of_two(div), 2U, 256U); > > > > > > > > ... as a single line? > > > > > > Yes, that's what I meant. > > > > Turns out, clamp really hates being passed roundup_pow_of_two() > > directly (see below). I think it's probably better if we leave > > them as-is, to avoid going the explicit cast route which Geert > > recommended against. > > I see, then ignore my comment on this matter in v9. > Perhaps add a comment in the code explaining that roundup_pow_of_two() > may not be unified with clamp()? I worry that commenting on why things are not done some other way at that location would detract from the legibility of the code itself. Perhaps we could use a cast after all, and write it out like this: div = clamp((u32)roundup_pow_of_two(div), 2U, 256U); which compiles fine without any warnings, accomplishes your "do it in a single line" desired behavior, and doesn't require me commenting on which linux library functions do or don't work well with others... :) Geert, what do you think? Thanks, --Gabriel
