[PATCH v2 1/4] iio: at91: fix adc_clk overflow
From: Josh Wu <hidden>
Date: 2013-08-11 11:04:28
Also in:
linux-iio
Subsystem:
iio subsystem and drivers, the rest · Maintainers:
Jonathan Cameron, Linus Torvalds
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 <redacted> Acked-by: Maxime Ripard <redacted> --- 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;
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1.7.10