[PATCH 07/12] i2c: meson: improve interrupt handler and detect spurious interrupts

[Jerome Brunet]

On Wed, 2017-03-08 at 07:47 +0100, Heiner Kallweit wrote:
> If state is STATE_IDLE no interrupt should occur. Detect this case and
> warn.
> In addition move resetting REG_CTRL_START bit to the start of the
> interrupt handler and remove a unneeded REG_CTRL_START bit reset
> in meson_i2c_xfer_msg.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1 at gmail.com>
> ---
>  drivers/i2c/busses/i2c-meson.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c
> index 81304840..b3b881f9 100644
> --- a/drivers/i2c/busses/i2c-meson.c
> +++ b/drivers/i2c/busses/i2c-meson.c
> @@ -233,7 +233,15 @@ static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
>  	dev_dbg(i2c->dev, "irq: state %d, pos %d, count %d, ctrl %08x\n",
>  		i2c->state, i2c->pos, i2c->count, ctrl);
>  
> -	if (ctrl & REG_CTRL_ERROR && i2c->state != STATE_IDLE) {
> +	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
> +
> +	if (i2c->state == STATE_IDLE) {
> +		dev_notice(i2c->dev, "spurious interrupt detected\n");
> +		spin_unlock(&i2c->lock);
> +		return IRQ_NONE;
> +	}

Does it really happen ? Did you see any specific issue you'd like to share ?
If not, I'm not a big fan of this change.

In any case, if it can be handled gracefully, I'd drop the trace in the
interrupt handler.


> +
> +	if (ctrl & REG_CTRL_ERROR) {
>  		/*
>  		 * The bit is set when the IGNORE_NAK bit is cleared
>  		 * and the device didn't respond. In this case, the
> @@ -276,15 +284,12 @@ static irqreturn_t meson_i2c_irq(int irqno, void
> *dev_id)
>  		i2c->state = STATE_IDLE;
>  		complete(&i2c->done);
>  		break;
> -	case STATE_IDLE:
> -		break;
>  	}
>  
>  out:
>  	if (i2c->state != STATE_IDLE) {
>  		/* Restart the processing */
>  		meson_i2c_write_tokens(i2c);
> -		meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
>  		meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START,
>  				   REG_CTRL_START);
>  	}
> @@ -344,9 +349,6 @@ static int meson_i2c_xfer_msg(struct meson_i2c *i2c,
> struct i2c_msg *msg,
>  	 */
>  	spin_lock_irqsave(&i2c->lock, flags);
>  
> -	/* Abort any active operation */
> -	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
> -
>  	if (!time_left) {
>  		i2c->state = STATE_IDLE;
>  		ret = -ETIMEDOUT;