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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

  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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