From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Josh Wu To: jic23@cam.ac.uk Cc: linux-arm-kernel@lists.infradead.org, linux-iio@vger.kernel.org, maxime.ripard@free-electrons.com, plagnioj@jcrosoft.com, nicolas.ferre@atmel.com, Josh Wu Subject: [PATCH 1/5] iio: at91: use adc_clk_khz to make the calculation not easy to large than u32. Date: Sun, 14 Jul 2013 16:04:25 +0800 Message-Id: <1373789069-11604-2-git-send-email-josh.wu@atmel.com> In-Reply-To: <1373789069-11604-1-git-send-email-josh.wu@atmel.com> References: <1373789069-11604-1-git-send-email-josh.wu@atmel.com> List-ID: for example, if adc_clk is 20Mhz and start-up time set as larger than 215us. then the calculation "st->startup_time * adc_clk_khz" will out of u32. In this patch, it will use khz unit for adc_clk, that avoids above problem. Signed-off-by: Josh Wu --- drivers/iio/adc/at91_adc.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c index e5b88d5..18bd54f 100644 --- a/drivers/iio/adc/at91_adc.c +++ b/drivers/iio/adc/at91_adc.c @@ -582,7 +582,7 @@ static const struct iio_info at91_adc_info = { static int at91_adc_probe(struct platform_device *pdev) { - unsigned int prsc, mstrclk, ticks, adc_clk, shtim; + unsigned int prsc, mstrclk, ticks, adc_clk, adc_clk_khz, shtim; int ret; struct iio_dev *idev; struct at91_adc_state *st; @@ -680,6 +680,7 @@ static int at91_adc_probe(struct platform_device *pdev) */ mstrclk = clk_get_rate(st->clk); adc_clk = clk_get_rate(st->adc_clk); + adc_clk_khz = adc_clk / 1000; prsc = (mstrclk / (2 * adc_clk)) - 1; if (!st->startup_time) { @@ -693,15 +694,15 @@ static int at91_adc_probe(struct platform_device *pdev) * defined in the electrical characteristics of the board, divided by 8. * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock */ - ticks = round_up((st->startup_time * adc_clk / - 1000000) - 1, 8) / 8; + ticks = round_up((st->startup_time * adc_clk_khz / + 1000) - 1, 8) / 8; /* * a minimal Sample and Hold Time is necessary for the ADC to guarantee * the best converted final value between two channels selection * The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock */ - shtim = round_up((st->sample_hold_time * adc_clk / - 1000000) - 1, 1); + shtim = round_up((st->sample_hold_time * adc_clk_khz / + 1000) - 1, 1); reg = AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL; reg |= AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP; -- 1.7.10