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| author | Daniel Kurtz <djkurtz@chromium.org> | 2012-11-15 17:43:30 +0530 |
|---|---|---|
| committer | Wolfram Sang <w.sang@pengutronix.de> | 2012-11-16 13:08:48 +0100 |
| commit | 9bcd04bfbbd5599de011176b846ed00ac15a234c (patch) | |
| tree | cdf492904dc6b6a457f01d0e268cb55a3cba2002 /drivers/i2c | |
| parent | 2693ac69880a33d4d9df6f128415b65e745f00ba (diff) | |
| download | linux-9bcd04bfbbd5599de011176b846ed00ac15a234c.tar.gz linux-9bcd04bfbbd5599de011176b846ed00ac15a234c.tar.bz2 linux-9bcd04bfbbd5599de011176b846ed00ac15a234c.zip | |
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.c | 10 |
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 */ |