[media] cafe_ccic: Fix hang in command write processing

{

	unsigned int rval;

	unsigned long flags;

	DEFINE_WAIT(the_wait);

	spin_lock_irqsave(&cam->dev_lock, flags);

	rval = TWSIC0_EN | ((addr << TWSIC0_SID_SHIFT) & TWSIC0_SID);

	cafe_reg_write(cam, REG_TWSIC1, rval);

	spin_unlock_irqrestore(&cam->dev_lock, flags);

	/* Unfortunately, reading TWSIC1 too soon after sending a command

	 * causes the device to die.

	 * Use a busy-wait because we often send a large quantity of small

	 * commands at-once; using msleep() would cause a lot of context

	 * switches which take longer than 2ms, resulting in a noticable

	 * boot-time and capture-start delays.

	 */

	mdelay(2);

	/*

	 * Time to wait for the write to complete.  THIS IS A RACY

	 * WAY TO DO IT, but the sad fact is that reading the TWSIC1

	 * register too quickly after starting the operation sends

	 * the device into a place that may be kinder and better, but

	 * which is absolutely useless for controlling the sensor.  In

	 * practice we have plenty of time to get into our sleep state

	 * before the interrupt hits, and the worst case is that we

	 * time out and then see that things completed, so this seems

	 * the best way for now.

	 */

	do {

		prepare_to_wait(&cam->smbus_wait, &the_wait,

				TASK_UNINTERRUPTIBLE);

		schedule_timeout(1); /* even 1 jiffy is too long */

		finish_wait(&cam->smbus_wait, &the_wait);

	} while (!cafe_smbus_write_done(cam));

#ifdef IF_THE_CAFE_HARDWARE_WORKED_RIGHT

	 * Another sad fact is that sometimes, commands silently complete but

	 * cafe_smbus_write_done() never becomes aware of this.

	 * This happens at random and appears to possible occur with any

	 * command.

	 * We don't understand why this is. We work around this issue

	 * with the timeout in the wait below, assuming that all commands

	 * complete within the timeout.

	 */

	wait_event_timeout(cam->smbus_wait, cafe_smbus_write_done(cam),

			CAFE_SMBUS_TIMEOUT);

#endif

	spin_lock_irqsave(&cam->dev_lock, flags);

	rval = cafe_reg_read(cam, REG_TWSIC1);

	spin_unlock_irqrestore(&cam->dev_lock, flags);