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? For those users of the omapconf tool I enjoy doing something like the following: <boot current, buggy behavior> omapconf dump prcm > old <boot with Tomi's flag enabled for all DPLLs by default> omapconf dump prcm > new diff -u old new This should reveal any deltas, assuming the board boots and doesn't let magic smoke out. Regards, Mike > > So, if you ask me, the whole flag is just for the purpose of keeping the > current drivers working, which could depend on the broken behavior. But > I think we cannot have such drivers (functional, at least) in any case, > as the clk-divider driver is broken and doesn't handle the errors the > dpll code currently returns for non-exact rates. > > 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
