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Date: Wed, 11 Mar 2015 13:08:12 +0100 From: Gaetan Hug <ghug@...uct.be> To: <thierry.reding@...il.com> CC: <linux-pwm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <shawn.guo@...aro.org>, <fabio.estevam@...escale.com>, Gaetan Hug <ghug@...uct.be> Subject: [PATCH RESEND] pwm: mxs: fix period divider computation The driver computes which clock divider it sould be using from the requested period. This computation assumes that the link between the register value and the actual divider value is raising 2 to the power of the registry value. div = 1 << regvalue This is true only for the first 5 values out of 8. Next values are 64, 256 and, 1024 - instead of 32, 64, 128. This affects only the users requesting a period > 0.04369s. Replace the computation with a look-up table. Signed-off-by: Gaetan Hug <ghug@...uct.be> Acked-by: Shawn Guo <shawn.guo@...aro.org> --- drivers/pwm/pwm-mxs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c index f75ecb0..c65e183 100644 --- a/drivers/pwm/pwm-mxs.c +++ b/drivers/pwm/pwm-mxs.c @@ -35,6 +35,8 @@ #define PERIOD_CDIV(div) (((div) & 0x7) << 20) #define PERIOD_CDIV_MAX 8 +static unsigned const int cdiv[PERIOD_CDIV_MAX] = {1, 2, 4, 8, 16, 64, 256, 1024}; + struct mxs_pwm_chip { struct pwm_chip chip; struct clk *clk; @@ -54,13 +56,13 @@ static int mxs_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, rate = clk_get_rate(mxs->clk); while (1) { - c = rate / (1 << div); + c = rate / cdiv[div]; c = c * period_ns; do_div(c, 1000000000); if (c < PERIOD_PERIOD_MAX) break; div++; - if (div > PERIOD_CDIV_MAX) + if (div >= PERIOD_CDIV_MAX) return -EINVAL; } -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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