From: josh.wu@atmel.com (Josh Wu)
To: linux-arm-kernel@lists.infradead.org
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 [thread overview]
Message-ID: <1373789069-11604-2-git-send-email-josh.wu@atmel.com> (raw)
In-Reply-To: <1373789069-11604-1-git-send-email-josh.wu@atmel.com>
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 <josh.wu@atmel.com>
---
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
next prev parent reply other threads:[~2013-07-14 8:04 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-14 8:04 [PATCH 0/5] iio: at91: Add touch screen support in at91 adc Josh Wu
2013-07-14 8:04 ` Josh Wu [this message]
2013-07-15 12:52 ` [PATCH 1/5] iio: at91: use adc_clk_khz to make the calculation not easy to large than u32 Maxime Ripard
2013-07-16 7:54 ` Josh Wu
2013-07-14 8:04 ` [PATCH 2/5] iio: at91: Use different prescal, startup mask in MR for different IP Josh Wu
2013-07-15 12:58 ` Maxime Ripard
2013-07-16 8:35 ` Josh Wu
2013-07-16 8:46 ` Nicolas Ferre
2013-07-16 11:20 ` Maxime Ripard
2013-07-16 11:30 ` Thomas Petazzoni
2013-07-16 19:03 ` Jonathan Cameron
2013-07-16 19:17 ` Thomas Petazzoni
2013-07-17 8:23 ` Nicolas Ferre
2013-07-17 8:12 ` Nicolas Ferre
2013-07-17 9:07 ` Josh Wu
2013-07-17 15:40 ` Maxime Ripard
2013-07-17 7:58 ` Nicolas Ferre
2013-07-17 10:09 ` Josh Wu
2013-07-20 9:35 ` Jonathan Cameron
2013-07-14 8:04 ` [PATCH 3/5] iio: at91: ADC start-up time calculation changed since at91sam9x5 Josh Wu
2013-07-20 9:39 ` Jonathan Cameron
2013-07-25 7:35 ` Josh Wu
2013-07-14 8:04 ` [PATCH 4/5] iio: at91: add an optional dt property for for adc clock hz Josh Wu
2013-07-15 13:06 ` Maxime Ripard
2013-07-16 7:55 ` Josh Wu
2013-07-16 10:30 ` Maxime Ripard
2013-07-16 11:16 ` Lars-Peter Clausen
2013-07-25 7:29 ` Josh Wu
2013-07-25 12:01 ` boris brezillon
2013-07-25 12:11 ` boris brezillon
2013-07-14 8:04 ` [PATCH 5/5] iio: at91: introduce touch screen support in iio adc driver Josh Wu
2013-07-15 13:15 ` Maxime Ripard
2013-07-16 9:09 ` Josh Wu
2013-07-16 11:43 ` Maxime Ripard
2013-07-20 9:57 ` Jonathan Cameron
2013-07-22 13:17 ` Mark Rutland
2013-07-25 7:56 ` Josh Wu
2013-07-25 16:45 ` Mark Rutland
2013-08-06 10:24 ` Josh Wu
2013-08-08 13:40 ` Mark Rutland
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