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authorDaniel Kurtz <djkurtz@chromium.org>2012-11-15 16:13:30 +0400
committerWolfram Sang <w.sang@pengutronix.de>2012-11-16 16:08:48 +0400
commit9bcd04bfbbd5599de011176b846ed00ac15a234c (patch)
treecdf492904dc6b6a457f01d0e268cb55a3cba2002 /drivers/i2c
parent2693ac69880a33d4d9df6f128415b65e745f00ba (diff)
downloadlinux-9bcd04bfbbd5599de011176b846ed00ac15a234c.tar.xz
i2c: s3c2410: grab adapter lock while changing i2c clock
We probably don't want to change I2C frequency while a transfer is in progress. The current implementation grabs a spinlock, but that only protected the writes to IICCON when starting a message, it didn't protect against clock changes in the middle of a transaction. Note: The i2c-core already grabs the adapter lock before calling s3c24xx_i2c_doxfer(), which ensures that only one caller is issuing a xfer at a time. This means it is not necessary to disable interrupts (spin_lock_irqsave) when changing frequencies, since there won't be any i2c interrupts if there is no on-going xfer. Lastly, i2c_lock_adapter() may cause the cpufreq_transition to sleep if if a xfer is in progress, but this is ok since cpufreq notifiers are called in a kernel thread, and there are already cases where it could sleep, such as when using i2c to update the output of a voltage regulator. Note: the cpufreq part of this change has no functional affect on exynos, where the i2c clock is independent of the cpufreq. But, there is a slight perfomance boost since we no longer need to lock/unlock an additional spinlock. Signed-off-by: Daniel Kurtz <djkurtz@chromium.org> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-s3c2410.c10
1 files changed, 2 insertions, 8 deletions
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 40e2d40bbdb5..86e60f598c51 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -60,7 +60,6 @@ enum s3c24xx_i2c_state {
};
struct s3c24xx_i2c {
- spinlock_t lock;
wait_queue_head_t wait;
unsigned int quirks;
unsigned int suspended:1;
@@ -541,8 +540,6 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
goto out;
}
- spin_lock_irq(&i2c->lock);
-
i2c->msg = msgs;
i2c->msg_num = num;
i2c->msg_ptr = 0;
@@ -551,7 +548,6 @@ static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,
s3c24xx_i2c_enable_irq(i2c);
s3c24xx_i2c_message_start(i2c, msgs);
- spin_unlock_irq(&i2c->lock);
timeout = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5);
@@ -741,7 +737,6 @@ 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;
@@ -755,9 +750,9 @@ static int s3c24xx_i2c_cpufreq_transition(struct notifier_block *nb,
if ((val == CPUFREQ_POSTCHANGE && delta_f < 0) ||
(val == CPUFREQ_PRECHANGE && delta_f > 0)) {
- spin_lock_irqsave(&i2c->lock, flags);
+ i2c_lock_adapter(&i2c->adap);
ret = s3c24xx_i2c_clockrate(i2c, &got);
- spin_unlock_irqrestore(&i2c->lock, flags);
+ i2c_unlock_adapter(&i2c->adap);
if (ret < 0)
dev_err(i2c->dev, "cannot find frequency\n");
@@ -962,7 +957,6 @@ static int s3c24xx_i2c_probe(struct platform_device *pdev)
i2c->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
i2c->tx_setup = 50;
- spin_lock_init(&i2c->lock);
init_waitqueue_head(&i2c->wait);
/* find the clock and enable it */