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>

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>
Daniel Silverstone · Ben Dooks
1 parent a192f7153b
Showing 7 changed files with 37 additions and 65 deletions Side-by-side Diff
arch/arm/mach-s3c2410/mach-bast.c
arch/arm/mach-s3c2410/mach-n30.c
arch/arm/mach-s3c2412/mach-jive.c
arch/arm/plat-s3c/dev-i2c0.c
arch/arm/plat-s3c/dev-i2c1.c
arch/arm/plat-s3c/include/plat/iic.h
drivers/i2c/busses/i2c-s3c2410.c
@@ -409,8 +409,7 @@
 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 */
@@ -340,8 +340,7 @@
 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
@@ -453,8 +453,7 @@
 /* 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,
 };
 /* 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 @@
 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,
 };
  
 /* 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 @@
 	.flags		= 0,
 	.bus_num	= 1,
 	.slave_addr	= 0x10,
-	.bus_freq	= 100*1000,
-	.max_freq	= 400*1000,
+	.frequency	= 100*1000,
 	.sda_delay	= 100,
 };
  
-/* 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);
 };
 /* 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 @@
 	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 @@
 	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;
  
-	/* ok, we may have to search for something suitable... */
+	target_frequency /= 1000; /* Target frequency now in KHz */
  
-	start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;
-	end = pdata->min_freq;
+	freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs);
  
-	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;
+	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);
...	...	@@ -409,8 +409,7 @@
409	409	static struct s3c2410_platform_i2c __initdata bast_i2c_info = {
410	410	.flags = 0,
411	411	.slave_addr = 0x10,
412		- .bus_freq = 100*1000,
413		- .max_freq = 130*1000,
	412	+ .frequency = 100*1000,
414	413	};
415	414
416	415	/* Asix AX88796 10/100 ethernet controller */
...	...	@@ -340,8 +340,7 @@
340	340	static struct s3c2410_platform_i2c n30_i2ccfg = {
341	341	.flags = 0,
342	342	.slave_addr = 0x10,
343		- .bus_freq = 10*1000,
344		- .max_freq = 10*1000,
	343	+ .frequency = 10*1000,
345	344	};
346	345
347	346	/* Lots of hardcoded stuff, but it sets up the hardware in a useful
...	...	@@ -453,8 +453,7 @@
453	453	/* I2C bus and device configuration. */
454	454
455	455	static struct s3c2410_platform_i2c jive_i2c_cfg __initdata = {
456		- .max_freq = 80 * 1000,
457		- .bus_freq = 50 * 1000,
	456	+ .frequency = 80 * 1000,
458	457	.flags = S3C_IICFLG_FILTER,
459	458	.sda_delay = 2,
460	459	};
1	1	/* linux/arch/arm/plat-s3c/dev-i2c0.c
2	2	*
3		- * Copyright 2008 Simtec Electronics
	3	+ * Copyright 2008,2009 Simtec Electronics
4	4	* Ben Dooks <ben@simtec.co.uk>
5	5	* http://armlinux.simtec.co.uk/
6	6	*
...	...	@@ -50,8 +50,7 @@
50	50	static struct s3c2410_platform_i2c default_i2c_data0 __initdata = {
51	51	.flags = 0,
52	52	.slave_addr = 0x10,
53		- .bus_freq = 100*1000,
54		- .max_freq = 400*1000,
	53	+ .frequency = 100*1000,
55	54	.sda_delay = 100,
56	55	};
57	56
1	1	/* linux/arch/arm/plat-s3c/dev-i2c1.c
2	2	*
3		- * Copyright 2008 Simtec Electronics
	3	+ * Copyright 2008,2009 Simtec Electronics
4	4	* Ben Dooks <ben@simtec.co.uk>
5	5	* http://armlinux.simtec.co.uk/
6	6	*
...	...	@@ -47,8 +47,7 @@
47	47	.flags = 0,
48	48	.bus_num = 1,
49	49	.slave_addr = 0x10,
50		- .bus_freq = 100*1000,
51		- .max_freq = 400*1000,
	50	+ .frequency = 100*1000,
52	51	.sda_delay = 100,
53	52	};
54	53
1		-/* arch/arm/mach-s3c2410/include/mach/iic.h
	1	+/* arch/arm/plat-s3c/include/plat/iic.h
2	2	*
3		- * Copyright (c) 2004 Simtec Electronics
	3	+ * Copyright 2004,2009 Simtec Electronics
4	4	* Ben Dooks <ben@simtec.co.uk>
5	5	*
6		- * S3C2410 - I2C Controller platfrom_device info
	6	+ * S3C - I2C Controller platform_device info
7	7	*
8	8	* This program is free software; you can redistribute it and/or modify
9	9	* it under the terms of the GNU General Public License version 2 as
10	10
11	11
...	...	@@ -15,19 +15,24 @@
15	15
16	16	#define S3C_IICFLG_FILTER (1<<0) /* enable s3c2440 filter */
17	17
18		-/* Notes:
19		- * 1) All frequencies are expressed in Hz
20		- * 2) A value of zero is `do not care`
21		-*/
22		-
	18	+/**
	19	+ * struct s3c2410_platform_i2c - Platform data for s3c I2C.
	20	+ * @bus_num: The bus number to use (if possible).
	21	+ * @flags: Any flags for the I2C bus (E.g. S3C_IICFLK_FILTER).
	22	+ * @slave_addr: The I2C address for the slave device (if enabled).
	23	+ * @frequency: The desired frequency in Hz of the bus. This is
	24	+ * guaranteed to not be exceeded. If the caller does
	25	+ * not care, use zero and the driver will select a
	26	+ * useful default.
	27	+ * @sda_delay: The delay (in ns) applied to SDA edges.
	28	+ * @cfg_gpio: A callback to configure the pins for I2C operation.
	29	+ */
23	30	struct s3c2410_platform_i2c {
24		- int bus_num; /* bus number to use */
	31	+ int bus_num;
25	32	unsigned int flags;
26		- unsigned int slave_addr; /* slave address for controller */
27		- unsigned long bus_freq; /* standard bus frequency */
28		- unsigned long max_freq; /* max frequency for the bus */
29		- unsigned long min_freq; /* min frequency for the bus */
30		- unsigned int sda_delay; /* pclks (s3c2440 only) */
	33	+ unsigned int slave_addr;
	34	+ unsigned long frequency;
	35	+ unsigned int sda_delay;
31	36
32	37	void (cfg_gpio)(struct platform_device dev);
33	38	};
1	1	/* linux/drivers/i2c/busses/i2c-s3c2410.c
2	2	*
3		- * Copyright (C) 2004,2005 Simtec Electronics
	3	+ * Copyright (C) 2004,2005,2009 Simtec Electronics
4	4	* Ben Dooks <ben@simtec.co.uk>
5	5	*
6	6	* S3C2410 I2C Controller
...	...	@@ -590,18 +590,6 @@
590	590	return clkin / (calc_divs * calc_div1);
591	591	}
592	592
593		-/* freq_acceptable
594		- *
595		- * test wether a frequency is within the acceptable range of error
596		-*/
597		-
598		-static inline int freq_acceptable(unsigned int freq, unsigned int wanted)
599		-{
600		- int diff = freq - wanted;
601		-
602		- return diff >= -2 && diff <= 2;
603		-}
604		-
605	593	/* s3c24xx_i2c_clockrate
606	594	*
607	595	* work out a divisor for the user requested frequency setting,
608	596
609	597
610	598
611	599
612	600
613	601
614	602
...	...	@@ -614,44 +602,28 @@
614	602	struct s3c2410_platform_i2c *pdata = i2c->dev->platform_data;
615	603	unsigned long clkin = clk_get_rate(i2c->clk);
616	604	unsigned int divs, div1;
	605	+ unsigned long target_frequency;
617	606	u32 iiccon;
618	607	int freq;
619		- int start, end;
620	608
621	609	i2c->clkrate = clkin;
622	610	clkin /= 1000; /* clkin now in KHz */
623	611
624		- dev_dbg(i2c->dev, "pdata %p, freq %lu %lu..%lu\n",
625		- pdata, pdata->bus_freq, pdata->min_freq, pdata->max_freq);
	612	+ dev_dbg(i2c->dev, "pdata desired frequency %lu\n", pdata->frequency);
626	613
627		- if (pdata->bus_freq != 0) {
628		- freq = s3c24xx_i2c_calcdivisor(clkin, pdata->bus_freq/1000,
629		- &div1, &divs);
630		- if (freq_acceptable(freq, pdata->bus_freq/1000))
631		- goto found;
632		- }
	614	+ target_frequency = pdata->frequency ? pdata->frequency : 100000;
633	615
634		- /* ok, we may have to search for something suitable... */
	616	+ target_frequency /= 1000; /* Target frequency now in KHz */
635	617
636		- start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;
637		- end = pdata->min_freq;
	618	+ freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs);
638	619
639		- start /= 1000;
640		- end /= 1000;
641		-
642		- /* search loop... */
643		-
644		- for (; start > end; start--) {
645		- freq = s3c24xx_i2c_calcdivisor(clkin, start, &div1, &divs);
646		- if (freq_acceptable(freq, start))
647		- goto found;
	620	+ if (freq > target_frequency) {
	621	+ dev_err(i2c->dev,
	622	+ "Unable to achieve desired frequency %luKHz." \
	623	+ " Lowest achievable %dKHz\n", target_frequency, freq);
	624	+ return -EINVAL;
648	625	}
649	626
650		- /* cannot find frequency spec */
651		-
652		- return -EINVAL;
653		-
654		- found:
655	627	*got = freq;
656	628
657	629	iiccon = readl(i2c->regs + S3C2410_IICCON);