Hi Haojian,
On Thu, 28 Apr 2011 12:02:36 +0800, Haojian Zhuang wrote:
> Both AP and CP are contained in Marvell PXA910 silicon. These two ARM
> cores are sharing one pair of I2C pins.
>
> In order to keep I2C transaction operated with atomic, hardware lock
> (RIPC) is required. Because of this, bus lock in AP side can't afford
> this requirement. Now hardware lock is appended.
I have no objection to the idea, but one question: when using the
hardware lock, isn't the software mutex redundant? I would expect that
you call the hardware_lock/unlock functions _instead_ of
rt_mutex_lock/unlock, rather than in addition to it. Or do you still
need the rt_mutex to prevent priority inversion?
>
> Signed-off-by: Haojian Zhuang <haojian.zhuang@xxxxxxxxxxx>
> Cc: Ben Dooks <ben-linux@xxxxxxxxx>
> ---
> drivers/i2c/i2c-core.c | 22 ++++++++++++++++++----
> include/linux/i2c.h | 3 +++
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 045ba6e..412c7a5 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -448,8 +448,11 @@ void i2c_lock_adapter(struct i2c_adapter *adapter)
>
> if (parent)
> i2c_lock_adapter(parent);
> - else
> + else {
> rt_mutex_lock(&adapter->bus_lock);
> + if (adapter->hardware_lock)
> + adapter->hardware_lock();
> + }
> }
> EXPORT_SYMBOL_GPL(i2c_lock_adapter);
>
> @@ -460,11 +463,19 @@ EXPORT_SYMBOL_GPL(i2c_lock_adapter);
> static int i2c_trylock_adapter(struct i2c_adapter *adapter)
> {
> struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
> + int ret = 0;
>
> if (parent)
> return i2c_trylock_adapter(parent);
> - else
> - return rt_mutex_trylock(&adapter->bus_lock);
> + else {
> + ret = rt_mutex_trylock(&adapter->bus_lock);
> + if (ret && adapter->hardware_trylock) {
> + ret = adapter->hardware_trylock();
> + if (!ret)
> + i2c_unlock_adapter(adapter);
> + }
> + return ret;
> + }
> }
>
> /**
> @@ -477,8 +488,11 @@ void i2c_unlock_adapter(struct i2c_adapter *adapter)
>
> if (parent)
> i2c_unlock_adapter(parent);
> - else
> + else {
> + if (adapter->hardware_unlock)
> + adapter->hardware_unlock();
> rt_mutex_unlock(&adapter->bus_lock);
> + }
> }
> EXPORT_SYMBOL_GPL(i2c_unlock_adapter);
>
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 06a8d9c..b283b4e 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -361,6 +361,9 @@ struct i2c_adapter {
>
> /* data fields that are valid for all devices */
> struct rt_mutex bus_lock;
> + void (*hardware_lock)(void);
> + void (*hardware_unlock)(void);
> + int (*hardware_trylock)(void);
>
> int timeout; /* in jiffies */
> int retries;
--
Jean Delvare
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