Quoting Tomi Valkeinen (2014-05-15 05:25:37) > On 15/05/14 09:08, Mike Turquette wrote: > > Quoting Tomi Valkeinen (2014-05-12 05:13:51) > >> On 12/05/14 15:02, Tero Kristo wrote: > >>> On 05/08/2014 12:06 PM, Tomi Valkeinen wrote: > >>>> The current DPLL code does not try to round the clock rate, and instead > >>>> returns an error if the requested clock rate cannot be produced exactly > >>>> by the DPLL. > >>>> > >>>> It could be argued that this is a bug, but as the current drivers may > >>>> depend on that behavior, a new flag 'ti,round-rate' is added which > >>>> enables clock rate rounding. > >>> > >>> Someone could probably argue that this flag is not a hardware feature, > >> > >> I fully agree. > >> > >>> but instead is used to describe linux-kernel behavior, and would > >>> probably be frowned upon by the DT enthusiasts. Othen than that, I like > >>> this approach better than a global setting, but would like second > >>> opinions here. > >> > >> I think the dpll code should always do rounding. That's what > >> round_rate() is supposed to do, afaik. The current behavior of not > >> rounding and returning an error is a bug in my opinion. > > > > From include/linux/clk.h: > > > > /** > > * clk_round_rate - adjust a rate to the exact rate a clock can provide > > * @clk: clock source > > * @rate: desired clock rate in Hz > > * > > * Returns rounded clock rate in Hz, or negative errno. > > */ > > long clk_round_rate(struct clk *clk, unsigned long rate); > > > > Definitely not rounding the rate is a bug, with respect to the API > > definition. Has anyone tried making the new flag as the default behavior > > and seeing if anything breaks? > > The v1 of the patch fixed the rounding unconditionally: > > http://article.gmane.org/gmane.linux.ports.arm.kernel/295077 > > Paul wanted it optional so that existing drivers would not break. No one > knows if there is such a driver, or what would the driver's code look > like that would cause an issue. > > And, as I've pointed out in the above thread, as clk-divider driver > doesn't an error code from the dpll driver, my opinion is that such > drivers would not work even now. > > I like v1 more. > > In any case, I hope we'd get something merged ASAP so that we fix the > display AM3xxx boards and we'd still have time to possibly find out if > some other driver breaks. Resurrecting this thread. Can we reach a consensus? I prefer V1 as well for the reasons stated above, and also since ti,round-rate isn't really describing the hardware at all in DT. We can always see how it goes and fix it up afterwards when everything explodes. Regards, Mike > > Tomi > > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
