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Commit 1dc6e729 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: das16: fix DMA size for short transfers 



Currently this driver alwasy programs the DMA transfer to be the allocated
size of the DMA buffer. When the async command 'stop_src' is TRIG_COUNT its
possible (likely) for the last transfer to be less than the buffer size.

Introduce a helper function, das16_ai_setup_dma(), to calculate the actual
size of the DMA transfer based on the number of samples remaining and the
number of unread samples.

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 42c44682

drivers/staging/comedi/drivers/das16.c

+25 −9
Original line number Diff line number Diff line
@@ -448,6 +448,28 @@ struct das16_private_struct { 
	unsigned int		timer_running:1;

};



static void das16_ai_setup_dma(struct comedi_device *dev,

			       struct comedi_subdevice *s,

			       unsigned int unread_samples)

{

	struct das16_private_struct *devpriv = dev->private;

	struct comedi_isadma *dma = devpriv->dma;

	struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];

	unsigned int max_samples = comedi_bytes_to_samples(s, desc->maxsize);

	unsigned int nsamples;



	/*

	 * Determine dma size based on the buffer size plus the number of

	 * unread samples and the number of samples remaining in the command.

	 */

	nsamples = comedi_nsamples_left(s, max_samples + unread_samples);

	if (nsamples > unread_samples) {

		nsamples -= unread_samples;

		desc->size = comedi_samples_to_bytes(s, nsamples);

		comedi_isadma_program(desc);

	}

}



static void das16_interrupt(struct comedi_device *dev)

{

	struct das16_private_struct *devpriv = dev->private;
@@ -486,13 +508,9 @@ static void das16_interrupt(struct comedi_device *dev) 
	nsamples = comedi_bytes_to_samples(s, nbytes);



	/* restart DMA if more samples are needed */

	if (nsamples && nsamples < comedi_nsamples_left(s, nsamples + 1)) {

		struct comedi_isadma_desc *nxt_desc;



	if (nsamples) {

		dma->cur_dma = 1 - dma->cur_dma;

		nxt_desc = &dma->desc[dma->cur_dma];

		nxt_desc->size = nxt_desc->maxsize;

		comedi_isadma_program(nxt_desc);

		das16_ai_setup_dma(dev, s, nsamples);

	}



	spin_unlock_irqrestore(&dev->spinlock, spin_flags);
@@ -672,7 +690,6 @@ static int das16_cmd_exec(struct comedi_device *dev, struct comedi_subdevice *s) 
	const struct das16_board *board = dev->board_ptr;

	struct das16_private_struct *devpriv = dev->private;

	struct comedi_isadma *dma = devpriv->dma;

	struct comedi_isadma_desc *desc = &dma->desc[0];

	struct comedi_async *async = s->async;

	struct comedi_cmd *cmd = &async->cmd;

	unsigned int byte;
@@ -721,8 +738,7 @@ static int das16_cmd_exec(struct comedi_device *dev, struct comedi_subdevice *s) 


	/* set up dma transfer */

	dma->cur_dma = 0;

	desc->size = desc->maxsize;

	comedi_isadma_program(desc);

	das16_ai_setup_dma(dev, s, 0);



	/*  set up timer */

	spin_lock_irqsave(&dev->spinlock, flags);