diff options
| author | Josh Wu <josh.wu@atmel.com> | 2013-08-27 15:28:00 +0400 |
|---|---|---|
| committer | Jonathan Cameron <jic23@kernel.org> | 2013-09-18 22:43:20 +0400 |
| commit | db10e201172f48dad29d81ee1fec96384f0eab35 (patch) | |
| tree | 8d99b9b0c2db7151988ba3f5c961763587e558a2 /drivers | |
| parent | c3cb718acc17f8e0d6b4b8d1f8ca9a20d1999159 (diff) | |
| download | linux-db10e201172f48dad29d81ee1fec96384f0eab35.tar.xz | |
iio: at91: fix adc_clk overflow
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@atmel.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/iio/adc/at91_adc.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c index 84be63bdf038..0f16b553e063 100644 --- a/drivers/iio/adc/at91_adc.c +++ b/drivers/iio/adc/at91_adc.c @@ -556,7 +556,7 @@ 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; @@ -649,6 +649,7 @@ 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) { @@ -662,15 +663,15 @@ 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) & st->registers->mr_prescal_mask; reg |= AT91_ADC_STARTUP_(ticks) & st->registers->mr_startup_mask; |