The adc_clk variable is currently defined using a 32-bits unsigned integer,
which will overflow under some very valid range of operations.
Such overflow will occur if, for example, the parent clock is set to a
20MHz frequency and the ADC startup time is larger than 215ns.
To fix this, introduce an intermediate variable holding the clock rate
in kHz.
Signed-off-by: Josh Wu <josh.wu@xxxxxxxxx>
Acked-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
v1 --> v2:
refined the commit message.
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 b6db6a0..9cf8ab5 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
--
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