From 5e5a21cf8e7756f668e7eb51ba99619136b79c4d Mon Sep 17 00:00:00 2001 From: H Hartley Sweeten Date: Tue, 13 Jan 2015 10:16:44 -0700 Subject: [PATCH] staging: comedi: das1800: tidy up das1800_ai_transfer_size() For aesthetics, pass the fill time 'ns' as a parameter to this function. Refactor this function to calculate the transfer size in 'samples' instead of 'bytes'. This removes the need to constantly multiply the values by the 'sample_size'. It also helps avoid any possible integer overflow issues. Use the comedi_nsamples_left() helper to limit the samples when cmd->stop_src is TRIG_COUNT. Use comedi_samples_to_bytes() to return the final DMA size in bytes. Signed-off-by: H Hartley Sweeten Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/das1800.c | 45 ++++++++++-------------- 1 file changed, 19 insertions(+), 26 deletions(-) diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c index c36ce0c73c68..5be5162dfe69 100644 --- a/drivers/staging/comedi/drivers/das1800.c +++ b/drivers/staging/comedi/drivers/das1800.c @@ -967,42 +967,35 @@ static void das1800_setup_counters(struct comedi_device *dev, } static unsigned int das1800_ai_transfer_size(struct comedi_device *dev, - struct comedi_subdevice *s) + struct comedi_subdevice *s, + unsigned int ns) { struct comedi_cmd *cmd = &s->async->cmd; - unsigned int size = DMA_BUF_SIZE; - unsigned int sample_size = comedi_bytes_per_sample(s); - unsigned int fill_time = 300000000; /* target time in nanoseconds for filling dma buffer */ - unsigned int max_size; /* maximum size we will allow for a transfer */ + unsigned int max_samples = comedi_bytes_to_samples(s, DMA_BUF_SIZE); + unsigned int samples; - /* make dma buffer fill in 0.3 seconds for timed modes */ + samples = max_samples; + + /* for timed modes, make dma buffer fill in 'ns' time */ switch (cmd->scan_begin_src) { - case TRIG_FOLLOW: /* not in burst mode */ + case TRIG_FOLLOW: /* not in burst mode */ if (cmd->convert_src == TRIG_TIMER) - size = (fill_time / cmd->convert_arg) * sample_size; + samples = ns / cmd->convert_arg; break; case TRIG_TIMER: - size = (fill_time / (cmd->scan_begin_arg * cmd->chanlist_len)) * - sample_size; - break; - default: - size = DMA_BUF_SIZE; + samples = ns / (cmd->scan_begin_arg * cmd->chanlist_len); break; } - /* set a minimum and maximum size allowed */ - max_size = DMA_BUF_SIZE; - /* if we are taking limited number of conversions, limit transfer size to that */ - if (cmd->stop_src == TRIG_COUNT && - cmd->stop_arg * cmd->chanlist_len * sample_size < max_size) - max_size = cmd->stop_arg * cmd->chanlist_len * sample_size; + /* limit samples to what is remaining in the command */ + samples = comedi_nsamples_left(s, samples); - if (size > max_size) - size = max_size; - if (size < sample_size) - size = sample_size; + if (samples > max_samples) + samples = max_samples; + if (samples < 1) + samples = 1; - return size; + return comedi_samples_to_bytes(s, samples); } static void das1800_ai_setup_dma(struct comedi_device *dev, @@ -1017,8 +1010,8 @@ static void das1800_ai_setup_dma(struct comedi_device *dev, devpriv->cur_dma = 0; - /* determine a reasonable dma transfer size */ - bytes = das1800_ai_transfer_size(dev, s); + /* determine a dma transfer size to fill buffer in 0.3 sec */ + bytes = das1800_ai_transfer_size(dev, s, 300000000); dma->size = bytes; das1800_isadma_program(dma); -- 2.20.1