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. Tomi
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