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authorDaniel Silverstone <dsilvers@simtec.co.uk>2009-03-13 09:53:46 -0400
committerBen Dooks <ben-linux@fluff.org>2009-04-07 05:18:33 -0400
commitc564e6ae6c5aa6e3995ff87ed4a32b4788ad5109 (patch)
treeb773106104d9897d945709d3bff8a56ff6586da8 /drivers/i2c
parenta192f7153bb33151f83440cd9c0442233a064bf1 (diff)
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>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-s3c2410.c50
1 files changed, 11 insertions, 39 deletions
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 @@
1/* linux/drivers/i2c/busses/i2c-s3c2410.c 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 * Ben Dooks <ben@simtec.co.uk> 4 * Ben Dooks <ben@simtec.co.uk>
5 * 5 *
6 * S3C2410 I2C Controller 6 * S3C2410 I2C Controller
@@ -590,18 +590,6 @@ static int s3c24xx_i2c_calcdivisor(unsigned long clkin, unsigned int wanted,
590 return clkin / (calc_divs * calc_div1); 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
598static 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/* s3c24xx_i2c_clockrate 593/* s3c24xx_i2c_clockrate
606 * 594 *
607 * work out a divisor for the user requested frequency setting, 595 * 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)
614 struct s3c2410_platform_i2c *pdata = i2c->dev->platform_data; 602 struct s3c2410_platform_i2c *pdata = i2c->dev->platform_data;
615 unsigned long clkin = clk_get_rate(i2c->clk); 603 unsigned long clkin = clk_get_rate(i2c->clk);
616 unsigned int divs, div1; 604 unsigned int divs, div1;
605 unsigned long target_frequency;
617 u32 iiccon; 606 u32 iiccon;
618 int freq; 607 int freq;
619 int start, end;
620 608
621 i2c->clkrate = clkin; 609 i2c->clkrate = clkin;
622 clkin /= 1000; /* clkin now in KHz */ 610 clkin /= 1000; /* clkin now in KHz */
623 611
624 dev_dbg(i2c->dev, "pdata %p, freq %lu %lu..%lu\n", 612 dev_dbg(i2c->dev, "pdata desired frequency %lu\n", pdata->frequency);
625 pdata, pdata->bus_freq, pdata->min_freq, pdata->max_freq);
626 613
627 if (pdata->bus_freq != 0) { 614 target_frequency = pdata->frequency ? pdata->frequency : 100000;
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 }
633
634 /* ok, we may have to search for something suitable... */
635
636 start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;
637 end = pdata->min_freq;
638 615
639 start /= 1000; 616 target_frequency /= 1000; /* Target frequency now in KHz */
640 end /= 1000;
641 617
642 /* search loop... */ 618 freq = s3c24xx_i2c_calcdivisor(clkin, target_frequency, &div1, &divs);
643 619
644 for (; start > end; start--) { 620 if (freq > target_frequency) {
645 freq = s3c24xx_i2c_calcdivisor(clkin, start, &div1, &divs); 621 dev_err(i2c->dev,
646 if (freq_acceptable(freq, start)) 622 "Unable to achieve desired frequency %luKHz." \
647 goto found; 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 *got = freq; 627 *got = freq;
656 628
657 iiccon = readl(i2c->regs + S3C2410_IICCON); 629 iiccon = readl(i2c->regs + S3C2410_IICCON);