mirror of
https://github.com/FEX-Emu/linux.git
synced 2024-12-25 02:48:21 +00:00
12f9ce4a51
The current implementation always round down the duty and period values, while it would be better to round them to the closest integer. These changes are needed in preparation of atomic update support to prevent a period/duty cycle drift when executing several times the 'pwm_get_state() / modify / pwm_apply_state()' sequence. Say you have an expected period of 3.333 us and a clk rate of 112.666667 MHz -- the clock frequency doesn't divide evenly, so the period (stashed in nanoseconds) shrinks when we convert to the register value and back, as follows: pwm_apply_state(): register = period * 112666667 / 1000000000; pwm_get_state(): period = register * 1000000000 / 112666667; or in other words: period = period * 112666667 / 1000000000 * 1000000000 / 112666667; which yields a sequence like: 3333 -> 3328 3328 -> 3319 3319 -> 3310 3310 -> 3301 3301 -> 3292 3292 -> ... (etc) ... With this patch, we'd see instead: period = div_round_closest(period * 112666667, 1000000000) * 1000000000 / 112666667; which yields a stable sequence: 3333 -> 3337 3337 -> 3337 3337 -> ... (etc) ... Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Reviewed-by: Brian Norris <briannorris@chromium.org> Tested-by: Brian Norris <briannorris@chromium.org> Tested-by: Heiko Stuebner <heiko@sntech.de> Signed-off-by: Thierry Reding <thierry.reding@gmail.com> |
||
---|---|---|
.. | ||
core.c | ||
Kconfig | ||
Makefile | ||
pwm-ab8500.c | ||
pwm-atmel-hlcdc.c | ||
pwm-atmel-tcb.c | ||
pwm-atmel.c | ||
pwm-bcm2835.c | ||
pwm-bcm-iproc.c | ||
pwm-bcm-kona.c | ||
pwm-berlin.c | ||
pwm-bfin.c | ||
pwm-brcmstb.c | ||
pwm-clps711x.c | ||
pwm-crc.c | ||
pwm-ep93xx.c | ||
pwm-fsl-ftm.c | ||
pwm-img.c | ||
pwm-imx.c | ||
pwm-jz4740.c | ||
pwm-lp3943.c | ||
pwm-lpc18xx-sct.c | ||
pwm-lpc32xx.c | ||
pwm-lpss-pci.c | ||
pwm-lpss-platform.c | ||
pwm-lpss.c | ||
pwm-lpss.h | ||
pwm-mtk-disp.c | ||
pwm-mxs.c | ||
pwm-omap-dmtimer.c | ||
pwm-pca9685.c | ||
pwm-puv3.c | ||
pwm-pxa.c | ||
pwm-rcar.c | ||
pwm-renesas-tpu.c | ||
pwm-rockchip.c | ||
pwm-samsung.c | ||
pwm-spear.c | ||
pwm-sti.c | ||
pwm-sun4i.c | ||
pwm-tegra.c | ||
pwm-tiecap.c | ||
pwm-tiehrpwm.c | ||
pwm-tipwmss.c | ||
pwm-twl-led.c | ||
pwm-twl.c | ||
pwm-vt8500.c | ||
sysfs.c |