mutex_lock in designware-i2c

[Rongrong Zou <zourongrong@gmail.com>]

Hi, baruch

I found a mutex lock in dw_i2c_dev for each adapter,
struct dw_i2c_dev {
         struct device           *dev;
         void __iomem            *base;
         struct completion       cmd_complete;
         struct mutex            lock;
         struct clk              *clk;

but there is another lock: adapter->bus_lock, this lock is also
for each adapter, why we need both of them ?

Regards,

Rongrong