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>

1 files changed, 11 insertions, 39 deletions

diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 9d797561de5f..e10a59e7db6f 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 @@ 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;
-        }
-
-        /* ok, we may have to search for something suitable... */
-
-        start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;
-        end = pdata->min_freq;
+        target_frequency = pdata->frequency ? pdata->frequency : 100000;
 
-        start /= 1000;
-        end /= 1000;
+        target_frequency /= 1000; /* Target frequency now in KHz */
 
-        /* search loop... */
+        freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs);
 
-        for (; start > end; start--) {
-                freq = s3c24xx_i2c_calcdivisor(clkin, start, &div1, &divs);
-                if (freq_acceptable(freq, start))
-                        goto found;
+        if (freq > target_frequency) {
+                dev_err(i2c->dev,
+                        "Unable to achieve desired frequency %luKHz."   \
+                        " Lowest achievable %dKHz\n", target_frequency, freq);
+                return -EINVAL;
         }
 
-        /* cannot find frequency spec */
-
-        return -EINVAL;
-
- found:
         *got = freq;
 
         iiccon = readl(i2c->regs + S3C2410_IICCON);