mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-08-22 17:01:14 +00:00
Code Issues Releases Wiki Activity

i2c-s3c2410: Simplify bus frequency calculation

Browse source 
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
Show stats Download patch file Download diff file Expand all files Collapse all files

3
arch/arm/mach-s3c2410/mach-bast.c
View file

@ -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 */

3
arch/arm/mach-s3c2410/mach-n30.c
View file

@ -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

3
arch/arm/mach-s3c2412/mach-jive.c
View file

@ -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,
};

5
arch/arm/plat-s3c/dev-i2c0.c
View file

@ -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,
};

5
arch/arm/plat-s3c/dev-i2c1.c
View file

@ -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,
};

33
arch/arm/plat-s3c/include/plat/iic.h
View file

@ -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);
};

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);