Hello Mike, hello Stephen, On Sat, Feb 21, 2015 at 11:40:23AM +0100, Uwe Kleine-König wrote: > The rate provided at the output of a clk-divider is calculated as: > > DIV_ROUND_UP(parent_rate, div) > > since commit b11d282dbea2 (clk: divider: fix rate calculation for > fractional rates). So to yield a rate not bigger than r parent_rate > must be <= r * div. > > The effect of choosing a parent rate that is too big as was done before > this patch results in wrongly ruling out good dividers. > > Note that this is not a complete fix as __clk_round_rate might return a > value >= its 2nd parameter. Also for dividers with > CLK_DIVIDER_ROUND_CLOSEST set the calculation is not accurate. But this > fixes the test case by Sascha Hauer that uses a chain of three dividers > under a fixed clock. > > Fixes: b11d282dbea2 (clk: divider: fix rate calculation for fractional rates) > Suggested-by: Sascha Hauer <[email protected]> > Signed-off-by: Uwe Kleine-König <[email protected]> Gentle ping.
IMHO this is patch should go into 4.0. Feedback for patches 2 and 3 (or the alternative to rip off specialised round-closest) would be very welcome, too. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
