i2c-s3c2410: Simplify bus frequency calculation
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>
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 9d79756..e10a59e 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -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 @@
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 @@
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);