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>

7 files changed, 37 insertions, 65 deletions

diff --git a/arch/arm/mach-s3c2410/mach-bast.c b/arch/arm/mach-s3c2410/mach-bast.c
index 01bd76725b92..4389c160f7d0 100644
--- a/arch/arm/mach-s3c2410/mach-bast.c
+++ b/arch/arm/mach-s3c2410/mach-bast.c
@@ -409,8 +409,7 @@ static struct platform_device bast_sio = {
 static struct s3c2410_platform_i2c __initdata bast_i2c_info = {
         .flags          = 0,
         .slave_addr     = 0x10,
-        .bus_freq       = 100*1000,
-        .max_freq       = 130*1000,
+        .frequency      = 100*1000,
 };
 
 /* Asix AX88796 10/100 ethernet controller */
diff --git a/arch/arm/mach-s3c2410/mach-n30.c b/arch/arm/mach-s3c2410/mach-n30.c
index 05a5e877b49b..2b83f8707710 100644
--- a/arch/arm/mach-s3c2410/mach-n30.c
+++ b/arch/arm/mach-s3c2410/mach-n30.c
@@ -340,8 +340,7 @@ static struct platform_device *n35_devices[] __initdata = {
 static struct s3c2410_platform_i2c n30_i2ccfg = {
         .flags          = 0,
         .slave_addr     = 0x10,
-        .bus_freq       = 10*1000,
-        .max_freq       = 10*1000,
+        .frequency      = 10*1000,
 };
 
 /* Lots of hardcoded stuff, but it sets up the hardware in a useful
diff --git a/arch/arm/mach-s3c2412/mach-jive.c b/arch/arm/mach-s3c2412/mach-jive.c
index 72c266aee141..332bd3263eaf 100644
--- a/arch/arm/mach-s3c2412/mach-jive.c
+++ b/arch/arm/mach-s3c2412/mach-jive.c
@@ -453,8 +453,7 @@ static struct spi_board_info __initdata jive_spi_devs[] = {
 /* I2C bus and device configuration. */
 
 static struct s3c2410_platform_i2c jive_i2c_cfg __initdata = {
-        .max_freq       = 80 * 1000,
-        .bus_freq       = 50 * 1000,
+        .frequency      = 80 * 1000,
         .flags          = S3C_IICFLG_FILTER,
         .sda_delay      = 2,
 };
diff --git a/arch/arm/plat-s3c/dev-i2c0.c b/arch/arm/plat-s3c/dev-i2c0.c
index 8eecb466ab4c..428372868fbb 100644
--- a/arch/arm/plat-s3c/dev-i2c0.c
+++ b/arch/arm/plat-s3c/dev-i2c0.c
@@ -1,6 +1,6 @@
 /* linux/arch/arm/plat-s3c/dev-i2c0.c
  *
- * Copyright 2008 Simtec Electronics
+ * Copyright 2008,2009 Simtec Electronics
  *      Ben Dooks <ben@simtec.co.uk>
  *      http://armlinux.simtec.co.uk/
  *
@@ -50,8 +50,7 @@ struct platform_device s3c_device_i2c0 = {
 static struct s3c2410_platform_i2c default_i2c_data0 __initdata = {
         .flags          = 0,
         .slave_addr     = 0x10,
-        .bus_freq       = 100*1000,
-        .max_freq       = 400*1000,
+        .frequency      = 100*1000,
         .sda_delay      = 100,
 };
 
diff --git a/arch/arm/plat-s3c/dev-i2c1.c b/arch/arm/plat-s3c/dev-i2c1.c
index 4536e5bb50e5..8349c462788c 100644
--- a/arch/arm/plat-s3c/dev-i2c1.c
+++ b/arch/arm/plat-s3c/dev-i2c1.c
@@ -1,6 +1,6 @@
 /* linux/arch/arm/plat-s3c/dev-i2c1.c
  *
- * Copyright 2008 Simtec Electronics
+ * Copyright 2008,2009 Simtec Electronics
  *      Ben Dooks <ben@simtec.co.uk>
  *      http://armlinux.simtec.co.uk/
  *
@@ -47,8 +47,7 @@ static struct s3c2410_platform_i2c default_i2c_data1 __initdata = {
         .flags          = 0,
         .bus_num        = 1,
         .slave_addr     = 0x10,
-        .bus_freq       = 100*1000,
-        .max_freq       = 400*1000,
+        .frequency      = 100*1000,
         .sda_delay      = 100,
 };
 
diff --git a/arch/arm/plat-s3c/include/plat/iic.h b/arch/arm/plat-s3c/include/plat/iic.h
index dc1dfcb9bc6c..67450f115748 100644
--- a/arch/arm/plat-s3c/include/plat/iic.h
+++ b/arch/arm/plat-s3c/include/plat/iic.h
@@ -1,9 +1,9 @@
-/* arch/arm/mach-s3c2410/include/mach/iic.h
+/* arch/arm/plat-s3c/include/plat/iic.h
  *
- * Copyright (c) 2004 Simtec Electronics
+ * Copyright 2004,2009 Simtec Electronics
  *      Ben Dooks <ben@simtec.co.uk>
  *
- * S3C2410 - I2C Controller platfrom_device info
+ * S3C - I2C Controller platform_device info
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -15,19 +15,24 @@
 
 #define S3C_IICFLG_FILTER       (1<<0)  /* enable s3c2440 filter */
 
-/* Notes:
- *      1) All frequencies are expressed in Hz
- *      2) A value of zero is `do not care`
-*/
-
+/**
+ *      struct s3c2410_platform_i2c - Platform data for s3c I2C.
+ *      @bus_num: The bus number to use (if possible).
+ *      @flags: Any flags for the I2C bus (E.g. S3C_IICFLK_FILTER).
+ *      @slave_addr: The I2C address for the slave device (if enabled).
+ *      @frequency: The desired frequency in Hz of the bus.  This is
+ *                  guaranteed to not be exceeded.  If the caller does
+ *                  not care, use zero and the driver will select a
+ *                  useful default.
+ *      @sda_delay: The delay (in ns) applied to SDA edges.
+ *      @cfg_gpio: A callback to configure the pins for I2C operation.
+ */
 struct s3c2410_platform_i2c {
-        int             bus_num;        /* bus number to use */
+        int             bus_num;
         unsigned int    flags;
-        unsigned int    slave_addr;     /* slave address for controller */
-        unsigned long   bus_freq;       /* standard bus frequency */
-        unsigned long   max_freq;       /* max frequency for the bus */
-        unsigned long   min_freq;       /* min frequency for the bus */
-        unsigned int    sda_delay;      /* pclks (s3c2440 only) */
+        unsigned int    slave_addr;
+        unsigned long   frequency;
+        unsigned int    sda_delay;
 
         void    (*cfg_gpio)(struct platform_device *dev);
 };
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);