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i2c-s3c2410: Simplify bus frequency calculation

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The platform data for the i2c-s3c2410 driver used to allow a min,
max and desired frequency for the I2C bus. This patch reduces it
to simply a desired frequency ceiling and corrects all the uses
of the platform data appropriately.

This means, for example, that on a system with a 66MHz fclk, a
request for 100KHz will achieve 65KHz which is safe and
acceptable, rather than 378KHz which it would have achieved
without this change.

Signed-off-by: Simtec Linux Team <linux@simtec.co.uk>
Signed-off-by: Daniel Silverstone <dsilvers@simtec.co.uk>
[ben-linux@fluff.org: tidy subject and description]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
This commit is contained in:
Daniel Silverstone
2009-03-13 13:53:46 +00:00
committed by Ben Dooks
parent a192f7153b
commit c564e6ae6c
7 changed files with 40 additions and 68 deletions
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56
drivers/i2c/busses/i2c-s3c2410.c
View File

@ -1,6 +1,6 @@
/* linux/drivers/i2c/busses/i2c-s3c2410.c
*
* Copyright (C) 2004,2005 Simtec Electronics
* Copyright (C) 2004,2005,2009 Simtec Electronics
* Ben Dooks <ben@simtec.co.uk>
*
* S3C2410 I2C Controller
@ -590,18 +590,6 @@ static int s3c24xx_i2c_calcdivisor(unsigned long clkin, unsigned int wanted,
return clkin / (calc_divs * calc_div1);
}
/* freq_acceptable
*
* test wether a frequency is within the acceptable range of error
*/
static inline int freq_acceptable(unsigned int freq, unsigned int wanted)
{
int diff = freq - wanted;
return diff >= -2 && diff <= 2;
}
/* s3c24xx_i2c_clockrate
*
* work out a divisor for the user requested frequency setting,
@ -614,44 +602,28 @@ static int s3c24xx_i2c_clockrate(struct s3c24xx_i2c *i2c, unsigned int *got)
struct s3c2410_platform_i2c *pdata = i2c->dev->platform_data;
unsigned long clkin = clk_get_rate(i2c->clk);
unsigned int divs, div1;
unsigned long target_frequency;
u32 iiccon;
int freq;
int start, end;
i2c->clkrate = clkin;
clkin /= 1000; /* clkin now in KHz */
dev_dbg(i2c->dev, "pdata %p, freq %lu %lu..%lu\n",
pdata, pdata->bus_freq, pdata->min_freq, pdata->max_freq);
dev_dbg(i2c->dev, "pdata desired frequency %lu\n", pdata->frequency);
if (pdata->bus_freq != 0) {
freq = s3c24xx_i2c_calcdivisor(clkin, pdata->bus_freq/1000,
&div1, &divs);
if (freq_acceptable(freq, pdata->bus_freq/1000))
goto found;
target_frequency = pdata->frequency ? pdata->frequency : 100000;
target_frequency /= 1000; /* Target frequency now in KHz */
freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs);
if (freq > target_frequency) {
dev_err(i2c->dev,
"Unable to achieve desired frequency %luKHz." \
" Lowest achievable %dKHz\n", target_frequency, freq);
return -EINVAL;
}
/* ok, we may have to search for something suitable... */
start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;
end = pdata->min_freq;
start /= 1000;
end /= 1000;
/* search loop... */
for (; start > end; start--) {
freq = s3c24xx_i2c_calcdivisor(clkin, start, &div1, &divs);
if (freq_acceptable(freq, start))
goto found;
}
/* cannot find frequency spec */
return -EINVAL;
found:
*got = freq;
iiccon = readl(i2c->regs + S3C2410_IICCON);