From c564e6ae6c5aa6e3995ff87ed4a32b4788ad5109 Mon Sep 17 00:00:00 2001 From: Daniel Silverstone Date: Fri, 13 Mar 2009 13:53:46 +0000 Subject: [PATCH] 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 Signed-off-by: Daniel Silverstone [ben-linux@fluff.org: tidy subject and description] Signed-off-by: Ben Dooks --- 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 | 56 +++++++--------------------- 7 files changed, 40 insertions(+), 68 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 * 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 * 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 * - * 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 * * 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);