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Commit ceb41be7 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: pcl816: fix short DMA transactions 



When the cmd->stop_src == TRIG_COUNT the last DMA transfer might be smaller
than the buffer size. This results in invalid data being added to the async
buffer.

Add a 'size' member to the DMA descriptor and initialize it with the
actual size of the DMA transfer. Use that in interrupt and ai subdevice
(*poll) function to return the proper number of samples. Use the
comedi_bytes_to_samples() helper to convert the byte size to comedi
samples in the interrupt handler.

Signed-off-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent a2c3966d

drivers/staging/comedi/drivers/pcl816.c

+18 −16
Original line number Diff line number Diff line
@@ -116,6 +116,7 @@ static const struct pcl816_board boardtypes[] = { 
struct pcl816_dma_desc {

	void *virt_addr;	/* virtual address of DMA buffer */

	dma_addr_t hw_addr;	/* hardware (bus) address of DMA buffer */

	unsigned int size;	/* transfer size (in bytes) */

};



struct pcl816_private {
@@ -158,30 +159,30 @@ static void pcl816_ai_setup_dma(struct comedi_device *dev, 
	struct pcl816_dma_desc *dma = &devpriv->dma_desc[0];

	struct comedi_cmd *cmd = &s->async->cmd;

	unsigned int dma_flags;

	unsigned int bytes;



	bytes = devpriv->hwdmasize;

	if (cmd->stop_src == TRIG_COUNT) {

		/*  how many */

		bytes = cmd->stop_arg * comedi_bytes_per_scan(s);

		dma->size = cmd->stop_arg * comedi_bytes_per_scan(s);



		/*  how many DMA pages we must fill */

		devpriv->dma_runs_to_end = bytes / devpriv->hwdmasize;

		devpriv->dma_runs_to_end = dma->size / devpriv->hwdmasize;



		/* on last dma transfer must be moved */

		devpriv->last_dma_run = bytes % devpriv->hwdmasize;

		devpriv->last_dma_run = dma->size % devpriv->hwdmasize;

		devpriv->dma_runs_to_end--;

		if (devpriv->dma_runs_to_end >= 0)

			bytes = devpriv->hwdmasize;

	} else

			dma->size = devpriv->hwdmasize;

	} else {

		dma->size = devpriv->hwdmasize;

		devpriv->dma_runs_to_end = -1;

	}



	devpriv->cur_dma = 0;

	set_dma_mode(devpriv->dma, DMA_MODE_READ);

	dma_flags = claim_dma_lock();

	clear_dma_ff(devpriv->dma);

	set_dma_addr(devpriv->dma, dma->hw_addr);

	set_dma_count(devpriv->dma, bytes);

	set_dma_count(devpriv->dma, dma->size);

	release_dma_lock(dma_flags);

	enable_dma(devpriv->dma);

}
@@ -199,13 +200,14 @@ static void pcl816_ai_setup_next_dma(struct comedi_device *dev, 
		/* switch dma bufs */

		devpriv->cur_dma = 1 - devpriv->cur_dma;

		dma = &devpriv->dma_desc[devpriv->cur_dma];

		if (devpriv->dma_runs_to_end)

			dma->size = devpriv->hwdmasize;

		else

			dma->size = devpriv->last_dma_run;

		set_dma_mode(devpriv->dma, DMA_MODE_READ);

		dma_flags = claim_dma_lock();

		set_dma_addr(devpriv->dma, dma->hw_addr);

		if (devpriv->dma_runs_to_end)

			set_dma_count(devpriv->dma, devpriv->hwdmasize);

		else

			set_dma_count(devpriv->dma, devpriv->last_dma_run);

		set_dma_count(devpriv->dma, dma->size);

		release_dma_lock(dma_flags);

		enable_dma(devpriv->dma);

	}
@@ -324,8 +326,8 @@ static irqreturn_t pcl816_interrupt(int irq, void *d) 
	struct comedi_subdevice *s = dev->read_subdev;

	struct pcl816_private *devpriv = dev->private;

	struct pcl816_dma_desc *dma = &devpriv->dma_desc[devpriv->cur_dma];

	unsigned int nsamples;

	unsigned int bufptr;

	unsigned int len;



	if (!dev->attached || !devpriv->ai_cmd_running) {

		pcl816_ai_clear_eoc(dev);
@@ -340,11 +342,11 @@ static irqreturn_t pcl816_interrupt(int irq, void *d) 


	pcl816_ai_setup_next_dma(dev, s);



	len = (devpriv->hwdmasize >> 1) - devpriv->ai_poll_ptr;

	nsamples = comedi_bytes_to_samples(s, dma->size) - devpriv->ai_poll_ptr;

	bufptr = devpriv->ai_poll_ptr;

	devpriv->ai_poll_ptr = 0;



	transfer_from_dma_buf(dev, s, dma->virt_addr, bufptr, len);

	transfer_from_dma_buf(dev, s, dma->virt_addr, bufptr, nsamples);



	pcl816_ai_clear_eoc(dev);
@@ -542,7 +544,7 @@ static int pcl816_ai_poll(struct comedi_device *dev, struct comedi_subdevice *s) 
	}



	/*  where is now DMA in buffer */

	top1 = devpriv->hwdmasize - top1;

	top1 = dma->size - top1;

	top1 >>= 1;		/*  sample position */

	top2 = top1 - devpriv->ai_poll_ptr;

	if (top2 < 1) {		/*  no new samples */