Julius, On Thu, Mar 26, 2015 at 4:30 PM, Julius Werner <jwerner@xxxxxxxxxxxx> wrote: > The Rockchip SPI driver currently calculates its clock rate divisor by > integer dividing the parent rate by the target rate, and then rounding > the result up to the next even number (since the divisor must be > even). > > Clock rate divisors should always be rounded up, so that the resulting > frequency is lower or equal to the target. This is correctly done in the > second step here but not in the first, so we still have a risk of > exceeding the desired target frequency (e.g. setting spi-max-frequency > to 40000000 with a parent clock of 99000000 could lead to a divisor of > 99000000 / 40000000 == 2 (which is even) that then results in an > effective frequency of 99000000 / 2 == 49500000 (potentially exceeding > the flash chip's specifications). > > This patch changes the division to round up to fix this problem. > > Signed-off-by: Julius Werner <jwerner@xxxxxxxxxxxx> > --- > drivers/spi/spi-rockchip.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Doug Anderson <dianders@xxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
