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SubjectRe: [PATCH 1/2] [i2c-bcm2835] Fully clean up hardware state machine after a timeout
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[Forward to Dave and Phil]

Am 30.10.23 um 17:21 schrieb mike.isely@cobaltdigital.com:
> From: Mike Isely <mike.isely@cobaltdigital.com>
>
> When the driver detects a timeout, there's no guarantee that the ISR
> would have fired. Thus after a timeout, it's the foreground that
> becomes responsible to reset the hardware state machine. The change
> here just duplicates what is already implemented in the ISR.
>
> Signed-off-by: Mike Isely <isely@pobox.com>
> ---
> drivers/i2c/busses/i2c-bcm2835.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
> index 8ce6d3f49551..96de875394e1 100644
> --- a/drivers/i2c/busses/i2c-bcm2835.c
> +++ b/drivers/i2c/busses/i2c-bcm2835.c
> @@ -345,42 +345,46 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
> static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
> int num)
> {
> struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> unsigned long time_left;
> int i;
>
> for (i = 0; i < (num - 1); i++)
> if (msgs[i].flags & I2C_M_RD) {
> dev_warn_once(i2c_dev->dev,
> "only one read message supported, has to be last\n");
> return -EOPNOTSUPP;
> }
>
> i2c_dev->curr_msg = msgs;
> i2c_dev->num_msgs = num;
> reinit_completion(&i2c_dev->completion);
>
> bcm2835_i2c_start_transfer(i2c_dev);
>
> time_left = wait_for_completion_timeout(&i2c_dev->completion,
> adap->timeout);
>
> bcm2835_i2c_finish_transfer(i2c_dev);
>
> if (!time_left) {
> + /* Since we can't trust the ISR to have cleaned up, do the
> + * full cleanup here... */
> bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
> BCM2835_I2C_C_CLEAR);
> + bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT |
> + BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE);
> dev_err(i2c_dev->dev, "i2c transfer timed out\n");
> return -ETIMEDOUT;
> }
>
> if (!i2c_dev->msg_err)
> return num;
>
> dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
>
> if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
> return -EREMOTEIO;
>
> return -EIO;
> }

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