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i2c: S3C24XX I2C frequency scaling support.
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Add support for CPU frequency scaling to the S3C24XX I2C driver.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
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Ben Dooks committed Jul 28, 2008
1 parent 1efe7c5 commit 61c7cff
Showing 1 changed file with 103 additions and 13 deletions.
116 changes: 103 additions & 13 deletions drivers/i2c/busses/i2c-s3c2410.c
Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>

#include <asm/hardware.h>
#include <asm/irq.h>
Expand Down Expand Up @@ -64,13 +65,18 @@ struct s3c24xx_i2c {
unsigned int tx_setup;

enum s3c24xx_i2c_state state;
unsigned long clkrate;

void __iomem *regs;
struct clk *clk;
struct device *dev;
struct resource *irq;
struct resource *ioarea;
struct i2c_adapter adap;

#ifdef CONFIG_CPU_FREQ
struct notifier_block freq_transition;
#endif
};

/* default platform data to use if not supplied in the platform_device
Expand Down Expand Up @@ -501,6 +507,9 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c, struct i2c_msg *msgs, int
unsigned long timeout;
int ret;

if (!readl(i2c->regs + S3C2410_IICCON) & S3C2410_IICCON_IRQEN)
return -EIO;

ret = s3c24xx_i2c_set_master(i2c);
if (ret != 0) {
dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
Expand Down Expand Up @@ -636,27 +645,28 @@ static inline int freq_acceptable(unsigned int freq, unsigned int wanted)
return (diff >= -2 && diff <= 2);
}

/* s3c24xx_i2c_getdivisor
/* s3c24xx_i2c_clockrate
*
* work out a divisor for the user requested frequency setting,
* either by the requested frequency, or scanning the acceptable
* range of frequencies until something is found
*/

static int s3c24xx_i2c_getdivisor(struct s3c24xx_i2c *i2c,
struct s3c2410_platform_i2c *pdata,
unsigned long *iicon,
unsigned int *got)
static int s3c24xx_i2c_clockrate(struct s3c24xx_i2c *i2c, unsigned int *got)
{
struct s3c2410_platform_i2c *pdata;
unsigned long clkin = clk_get_rate(i2c->clk);

unsigned int divs, div1;
u32 iiccon;
int freq;
int start, end;

i2c->clkrate = clkin;

pdata = s3c24xx_i2c_get_platformdata(i2c->adap.dev.parent);
clkin /= 1000; /* clkin now in KHz */

dev_dbg(i2c->dev, "pdata %p, freq %lu %lu..%lu\n",
dev_dbg(i2c->dev, "pdata %p, freq %lu %lu..%lu\n",
pdata, pdata->bus_freq, pdata->min_freq, pdata->max_freq);

if (pdata->bus_freq != 0) {
Expand Down Expand Up @@ -688,11 +698,79 @@ static int s3c24xx_i2c_getdivisor(struct s3c24xx_i2c *i2c,

found:
*got = freq;
*iicon |= (divs-1);
*iicon |= (div1 == 512) ? S3C2410_IICCON_TXDIV_512 : 0;

iiccon = readl(i2c->regs + S3C2410_IICCON);
iiccon &= ~(S3C2410_IICCON_SCALEMASK | S3C2410_IICCON_TXDIV_512);
iiccon |= (divs-1);

if (div1 == 512)
iiccon |= S3C2410_IICCON_TXDIV_512;

writel(iiccon, i2c->regs + S3C2410_IICCON);

return 0;
}

#ifdef CONFIG_CPU_FREQ

#define freq_to_i2c(_n) container_of(_n, struct s3c24xx_i2c, freq_transition)

static int s3c24xx_i2c_cpufreq_transition(struct notifier_block *nb,
unsigned long val, void *data)
{
struct s3c24xx_i2c *i2c = freq_to_i2c(nb);
unsigned long flags;
unsigned int got;
int delta_f;
int ret;

delta_f = clk_get_rate(i2c->clk) - i2c->clkrate;

/* if we're post-change and the input clock has slowed down
* or at pre-change and the clock is about to speed up, then
* adjust our clock rate. <0 is slow, >0 speedup.
*/

if ((val == CPUFREQ_POSTCHANGE && delta_f < 0) ||
(val == CPUFREQ_PRECHANGE && delta_f > 0)) {
spin_lock_irqsave(&i2c->lock, flags);
ret = s3c24xx_i2c_clockrate(i2c, &got);
spin_unlock_irqrestore(&i2c->lock, flags);

if (ret < 0)
dev_err(i2c->dev, "cannot find frequency\n");
else
dev_info(i2c->dev, "setting freq %d\n", got);
}

return 0;
}

static inline int s3c24xx_i2c_register_cpufreq(struct s3c24xx_i2c *i2c)
{
i2c->freq_transition.notifier_call = s3c24xx_i2c_cpufreq_transition;

return cpufreq_register_notifier(&i2c->freq_transition,
CPUFREQ_TRANSITION_NOTIFIER);
}

static inline void s3c24xx_i2c_deregister_cpufreq(struct s3c24xx_i2c *i2c)
{
cpufreq_unregister_notifier(&i2c->freq_transition,
CPUFREQ_TRANSITION_NOTIFIER);
}

#else
static inline int s3c24xx_i2c_register_cpufreq(struct s3c24xx_i2c *i2c)
{
return 0;
}

static inline void s3c24xx_i2c_deregister_cpufreq(struct s3c24xx_i2c *i2c)
{
}
#endif

/* s3c24xx_i2c_init
*
* initialise the controller, set the IO lines and frequency
Expand All @@ -719,9 +797,12 @@ static int s3c24xx_i2c_init(struct s3c24xx_i2c *i2c)

dev_info(i2c->dev, "slave address 0x%02x\n", pdata->slave_addr);

writel(iicon, i2c->regs + S3C2410_IICCON);

/* we need to work out the divisors for the clock... */

if (s3c24xx_i2c_getdivisor(i2c, pdata, &iicon, &freq) != 0) {
if (s3c24xx_i2c_clockrate(i2c, &freq) != 0) {
writel(0, i2c->regs + S3C2410_IICCON);
dev_err(i2c->dev, "cannot meet bus frequency required\n");
return -EINVAL;
}
Expand All @@ -730,8 +811,6 @@ static int s3c24xx_i2c_init(struct s3c24xx_i2c *i2c)

dev_info(i2c->dev, "bus frequency set to %d KHz\n", freq);
dev_dbg(i2c->dev, "S3C2410_IICCON=0x%02lx\n", iicon);

writel(iicon, i2c->regs + S3C2410_IICCON);

/* check for s3c2440 i2c controller */

Expand Down Expand Up @@ -835,6 +914,12 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
dev_dbg(&pdev->dev, "irq resource %p (%lu)\n", res,
(unsigned long)res->start);

ret = s3c24xx_i2c_register_cpufreq(i2c);
if (ret < 0) {
dev_err(&pdev->dev, "failed to register cpufreq notifier\n");
goto err_irq;
}

/* Note, previous versions of the driver used i2c_add_adapter()
* to add the bus at any number. We now pass the bus number via
* the platform data, so if unset it will now default to always
Expand All @@ -846,14 +931,17 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
ret = i2c_add_numbered_adapter(&i2c->adap);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add bus to i2c core\n");
goto err_irq;
goto err_cpufreq;
}

platform_set_drvdata(pdev, i2c);

dev_info(&pdev->dev, "%s: S3C I2C adapter\n", i2c->adap.dev.bus_id);
return 0;

err_cpufreq:
s3c24xx_i2c_deregister_cpufreq(i2c);

err_irq:
free_irq(i2c->irq->start, i2c);

Expand Down Expand Up @@ -881,6 +969,8 @@ static int s3c24xx_i2c_remove(struct platform_device *pdev)
{
struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev);

s3c24xx_i2c_deregister_cpufreq(i2c);

i2c_del_adapter(&i2c->adap);
free_irq(i2c->irq->start, i2c);

Expand Down

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