I2C: Rework i2c-s3c2410 frequency calculator to be much simpler.
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@xxxxxxxxxxxx>
Signed-off-by: Daniel Silverstone <dsilvers@xxxxxxxxxxxx>
---
arch/arm/mach-s3c2410/mach-bast.c | 3 --
arch/arm/mach-s3c2410/mach-n30.c | 3 --
arch/arm/mach-s3c2412/mach-jive.c | 3 --
arch/arm/plat-s3c/dev-i2c0.c | 5 +--
arch/arm/plat-s3c/dev-i2c1.c | 5 +--
arch/arm/plat-s3c/include/plat/iic.h | 33 +++++++++++++----------
drivers/i2c/busses/i2c-s3c2410.c | 50 +++++++----------------------------
7 files changed, 36 insertions(+), 66 deletions(-)
Index: b/drivers/i2c/busses/i2c-s3c2410.c
===================================================================
--- a/drivers/i2c/busses/i2c-s3c2410.c 2009-02-12 09:58:30.866611025 +0000
+++ b/drivers/i2c/busses/i2c-s3c2410.c 2009-02-12 10:24:29.530615073 +0000
@@ -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@xxxxxxxxxxxx>
*
* S3C2410 I2C Controller
@@ -590,18 +590,6 @@ static int s3c24xx_i2c_calcdivisor(unsig
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 +602,26 @@ static int s3c24xx_i2c_clockrate(struct
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;
-
- start /= 1000;
- end /= 1000;
+ target_frequency = pdata->frequency ? pdata->frequency : 100000;
- /* 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);
Index: b/arch/arm/plat-s3c/include/plat/iic.h
===================================================================
--- a/arch/arm/plat-s3c/include/plat/iic.h 2009-02-12 09:43:10.599030214 +0000
+++ b/arch/arm/plat-s3c/include/plat/iic.h 2009-02-12 10:24:29.502615860 +0000
@@ -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@xxxxxxxxxxxx>
*
- * 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);
};
Index: b/arch/arm/plat-s3c/dev-i2c0.c
===================================================================
--- a/arch/arm/plat-s3c/dev-i2c0.c 2009-02-12 09:58:30.866611025 +0000
+++ b/arch/arm/plat-s3c/dev-i2c0.c 2009-02-12 10:24:29.450615087 +0000
@@ -1,6 +1,6 @@
/* linux/arch/arm/plat-s3c/dev-i2c0.c
*
- * Copyright 2008 Simtec Electronics
+ * Copyright 2008,2009 Simtec Electronics
* Ben Dooks <ben@xxxxxxxxxxxx>
* 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,
};
Index: b/arch/arm/plat-s3c/dev-i2c1.c
===================================================================
--- a/arch/arm/plat-s3c/dev-i2c1.c 2009-02-12 09:58:30.910131374 +0000
+++ b/arch/arm/plat-s3c/dev-i2c1.c 2009-02-12 10:24:29.466616700 +0000
@@ -1,6 +1,6 @@
/* linux/arch/arm/plat-s3c/dev-i2c1.c
*
- * Copyright 2008 Simtec Electronics
+ * Copyright 2008,2009 Simtec Electronics
* Ben Dooks <ben@xxxxxxxxxxxx>
* http://armlinux.simtec.co.uk/
*
@@ -47,8 +47,7 @@ static struct s3c2410_platform_i2c defau
.flags = 0,
.bus_num = 1,
.slave_addr = 0x10,
- .bus_freq = 100*1000,
- .max_freq = 400*1000,
+ .frequency = 100*1000,
.sda_delay = 100,
};
Index: b/arch/arm/mach-s3c2410/mach-bast.c
===================================================================
--- a/arch/arm/mach-s3c2410/mach-bast.c 2009-02-12 09:42:49.254613471 +0000
+++ b/arch/arm/mach-s3c2410/mach-bast.c 2009-02-12 10:24:29.394616021 +0000
@@ -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 */
Index: b/arch/arm/mach-s3c2410/mach-n30.c
===================================================================
--- a/arch/arm/mach-s3c2410/mach-n30.c 2009-02-12 09:42:49.842111069 +0000
+++ b/arch/arm/mach-s3c2410/mach-n30.c 2009-02-12 10:24:29.410614435 +0000
@@ -340,8 +340,7 @@ static struct platform_device *n35_devic
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
Index: b/arch/arm/mach-s3c2412/mach-jive.c
===================================================================
--- a/arch/arm/mach-s3c2412/mach-jive.c 2009-02-12 09:42:50.430341907 +0000
+++ b/arch/arm/mach-s3c2412/mach-jive.c 2009-02-12 10:24:29.430615021 +0000
@@ -453,8 +453,7 @@ static struct spi_board_info __initdata
/* 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,
};
--
Daniel Silverstone http://www.simtec.co.uk/
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