From ceb41be712b68fac4ac834120a80fc3cb8e5ac37 Mon Sep 17 00:00:00 2001 From: H Hartley Sweeten Date: Mon, 12 Jan 2015 10:56:04 -0700 Subject: [PATCH] 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: H Hartley Sweeten Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/pcl816.c | 34 +++++++++++++------------ 1 file changed, 18 insertions(+), 16 deletions(-) diff --git a/drivers/staging/comedi/drivers/pcl816.c b/drivers/staging/comedi/drivers/pcl816.c index 1b760858c72a..f880cb994074 100644 --- a/drivers/staging/comedi/drivers/pcl816.c +++ b/drivers/staging/comedi/drivers/pcl816.c @@ -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 */ -- 2.20.1