Re: [PATCH v2 3/4] i2c: i2c-ibm-iic: Implements transfer abortion

[Gregory CLEMENT <gregory.clement-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

Hi Jean-Jacques,

I have just found these emails in may draft box, and I thought I have
already sent them. However I didn't find anything relevant about the
driver itslef, but only few nitpick. So either your change are goods,
or I missed the important points. The final judgment belongs ton
Wolfram :)


On 22/11/2013 09:58, jean-jacques hiblot wrote:
> Clean-up properly when a transfer fails for whatever reason.
> Cancel the transfer when the process is signaled.
> 
> Signed-off-by: jean-jacques hiblot <jjhiblot-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  drivers/i2c/busses/i2c-ibm_iic.c | 144 +++++++++------------------------------
>  drivers/i2c/busses/i2c-ibm_iic.h |   2 +-
>  2 files changed, 35 insertions(+), 111 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-ibm_iic.c b/drivers/i2c/busses/i2c-ibm_iic.c
> index 2bb55b3..a3f3f1b 100644
> --- a/drivers/i2c/busses/i2c-ibm_iic.c
> +++ b/drivers/i2c/busses/i2c-ibm_iic.c
> @@ -334,119 +334,25 @@ static irqreturn_t iic_handler(int irq, void *dev_id)
>  }
>  
>  /*
> - * Get master transfer result and clear errors if any.
> - * Returns the number of actually transferred bytes or error (<0)
> - */
> -static int iic_xfer_result(struct ibm_iic_private* dev)
> -{
> -	struct iic_regs __iomem *iic = dev->vaddr;
> -
> -	if (unlikely(in_8(&iic->sts) & STS_ERR)){
> -		DBG(dev, "xfer error, EXTSTS = 0x%02x\n",
> -			in_8(&iic->extsts));
> -
> -		/* Clear errors and possible pending IRQs */
> -		out_8(&iic->extsts, EXTSTS_IRQP | EXTSTS_IRQD |
> -			EXTSTS_LA | EXTSTS_ICT | EXTSTS_XFRA);
> -
> -		/* Flush master data buffer */
> -		out_8(&iic->mdcntl, in_8(&iic->mdcntl) | MDCNTL_FMDB);
> -
> -		/* Is bus free?
> -		 * If error happened during combined xfer
> -		 * IIC interface is usually stuck in some strange
> -		 * state, the only way out - soft reset.
> -		 */
> -		if ((in_8(&iic->extsts) & EXTSTS_BCS_MASK) != EXTSTS_BCS_FREE){
> -			DBG(dev, "bus is stuck, resetting\n");
> -			iic_dev_reset(dev);
> -		}
> -		return -EREMOTEIO;
> -	}
> -	else
> -		return in_8(&iic->xfrcnt) & XFRCNT_MTC_MASK;
> -}
> -
> -/*
>   * Try to abort active transfer.
>   */
> -static void iic_abort_xfer(struct ibm_iic_private* dev)
> +static void iic_abort_xfer(struct ibm_iic_private *dev)
>  {
> -	struct iic_regs __iomem *iic = dev->vaddr;
> -	unsigned long x;
> -
> -	DBG(dev, "iic_abort_xfer\n");
> +	struct device *device = dev->adap.dev.parent;
> +	unsigned long end;
>  
> -	out_8(&iic->cntl, CNTL_HMT);
> +	DBG(dev, "aborting transfer\n");
> +	/* transfer should be aborted within 10ms */
> +	end = jiffies + 10;
> +	dev->abort = 1;
>  
> -	/*
> -	 * Wait for the abort command to complete.
> -	 * It's not worth to be optimized, just poll (timeout >= 1 tick)
> -	 */
> -	x = jiffies + 2;
> -	while ((in_8(&iic->extsts) & EXTSTS_BCS_MASK) != EXTSTS_BCS_FREE){
> -		if (time_after(jiffies, x)){
> -			DBG(dev, "abort timeout, resetting...\n");
> -			iic_dev_reset(dev);
> -			return;
> -		}
> +	while (time_after(end, jiffies) && !dev->transfer_complete)
>  		schedule();
> -	}
>  
> -	/* Just to clear errors */
> -	iic_xfer_result(dev);
> -}
> -
> -/*
> - * Wait for master transfer to complete.
> - * It puts current process to sleep until we get interrupt or timeout expires.
> - * Returns the number of transferred bytes or error (<0)
> - */
> -static int iic_wait_for_tc(struct ibm_iic_private* dev){
> -
> -	struct iic_regs __iomem *iic = dev->vaddr;
> -	int ret = 0;
> -
> -	if (dev->irq >= 0){
> -		/* Interrupt mode */
> -		ret = wait_event_interruptible_timeout(dev->wq,
> -			!(in_8(&iic->sts) & STS_PT), dev->adap.timeout);
> -
> -		if (unlikely(ret < 0))
> -			DBG(dev, "wait interrupted\n");
> -		else if (unlikely(in_8(&iic->sts) & STS_PT)){
> -			DBG(dev, "wait timeout\n");
> -			ret = -ETIMEDOUT;
> -		}
> -	}
> -	else {
> -		/* Polling mode */
> -		unsigned long x = jiffies + dev->adap.timeout;
> -
> -		while (in_8(&iic->sts) & STS_PT){
> -			if (unlikely(time_after(jiffies, x))){
> -				DBG(dev, "poll timeout\n");
> -				ret = -ETIMEDOUT;
> -				break;
> -			}
> -
> -			if (unlikely(signal_pending(current))){
> -				DBG(dev, "poll interrupted\n");
> -				ret = -ERESTARTSYS;
> -				break;
> -			}
> -			schedule();
> -		}
> +	if (!dev->transfer_complete) {
> +		dev_err(device, "abort operation failed\n");

What about using the ERR macro you introduce in the previous patch?

> +		iic_dev_reset(dev);
>  	}
> -
> -	if (unlikely(ret < 0))
> -		iic_abort_xfer(dev);
> -	else
> -		ret = iic_xfer_result(dev);
> -
> -	DBG2(dev, "iic_wait_for_tc -> %d\n", ret);
> -
> -	return ret;
>  }
>  
>  /*
> @@ -470,6 +376,13 @@ static int iic_xfer_bytes(struct ibm_iic_private *dev)
>  			    EXTSTS_ICT | EXTSTS_XFRA);
>  	out_8(&iic->sts, STS_IRQA | STS_SCMP);
>  
> +	if (dev->status == -ECANCELED) {
> +		DBG(dev, "abort completed\n");
> +		dev->transfer_complete = 1;
> +		complete(&dev->iic_compl);
> +		return dev->status;
> +	}
> +
>  	if ((status & STS_ERR) ||
>  	    (ext_status & (EXTSTS_LA | EXTSTS_ICT | EXTSTS_XFRA))) {
>  		DBG(dev, "status 0x%x\n", status);
> @@ -571,7 +484,14 @@ static int iic_xfer_bytes(struct ibm_iic_private *dev)
>  	/* actually start the transfer of the current data chunk */
>  	out_8(&iic->cntl, cntl | CNTL_PT);
>  
> -	return 0;
> +	/* The transfer must be aborted. */
> +	if (dev->abort) {
> +		DBG(dev, "aborting\n");
> +		out_8(&iic->cntl, CNTL_HMT);
> +		dev->status = -ECANCELED;
> +	}
> +
> +	return dev->status;
>  }
>  
>  /*
> @@ -673,6 +593,7 @@ static int iic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>  	dev->current_byte = dev->current_msg = dev->current_byte_rx = 0;
>  	dev->transfer_complete = 0;
>  	dev->status = 0;
> +	dev->abort = 0;
>  	dev->msgs = msgs;
>  	dev->num_msgs = num;
>  
> @@ -710,8 +631,9 @@ static int iic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>  		/*  wait for the transfer to complete */
>  		ret = wait_for_completion_interruptible_timeout(
>  			&dev->iic_compl, num * HZ);
> -		/* mask the interrupts */
> -		out_8(&iic->intmsk, 0);
> +		/* we don't mask the interrupts here because we may
> +		* need them to abort the transfer gracefully
> +		*/
nitpick:wrong multiline comment style

>  	}
>  
>  	if (ret == 0) {
> @@ -720,11 +642,15 @@ static int iic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>  	} else if (ret < 0) {
>  		if (ret == -ERESTARTSYS)
>  			ERR(dev, "transfer interrupted\n");
> +		iic_abort_xfer(dev);
>  	} else {
>  		/* Transfer is complete */
>  		ret = (dev->status) ? dev->status : num;
>  	}
>  
> +	/* mask the interrupts */
> +	out_8(&iic->intmsk, 0);
> +
>  	return ret;
>  }
>  
> @@ -821,8 +747,6 @@ static int iic_probe(struct platform_device *ofdev)
>  		goto error_cleanup;
>  	}
>  
> -	init_waitqueue_head(&dev->wq);
> -
>  	dev->irq = iic_request_irq(ofdev, dev);
>  	if (!dev->irq)
>  		dev_info(&ofdev->dev, "using polling mode\n");
> diff --git a/drivers/i2c/busses/i2c-ibm_iic.h b/drivers/i2c/busses/i2c-ibm_iic.h
> index 76c476a..0ee28a9 100644
> --- a/drivers/i2c/busses/i2c-ibm_iic.h
> +++ b/drivers/i2c/busses/i2c-ibm_iic.h
> @@ -47,7 +47,6 @@ struct iic_regs {
>  struct ibm_iic_private {
>  	struct i2c_adapter adap;
>  	struct iic_regs __iomem *vaddr;
> -	wait_queue_head_t wq;
>  	int irq;
>  	int fast_mode;
>  	u8  clckdiv;
> @@ -58,6 +57,7 @@ struct ibm_iic_private {
>  	int current_byte_rx;
>  	int transfer_complete;
>  	int status;
> +	int abort;
>  	struct completion iic_compl;
>  };
>  
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com