From 9bcd04bfbbd5599de011176b846ed00ac15a234c Mon Sep 17 00:00:00 2001 From: Daniel Kurtz Date: Thu, 15 Nov 2012 17:43:30 +0530 Subject: [PATCH] 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 Signed-off-by: Naveen Krishna Chatradhi Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-s3c2410.c | 10 ++-------- 1 file 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 */