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staging: comedi: dt282x: avoid calculating the timer divisor multiple times

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A common timer is used for analog input and output async commands. The
(*do_cmdtest) for both subdevices calculates the divisor as part of
Step 4 when validating the trigger arguments. The divisor is calculated
again in the (*do_cmd) for both subdevices in order to set the timer.

The comedi core only calls the (*do_cmd) is called after a successful
(*do_cmdtest). Save the divisor from the (*do_cmdtest) in the private
data and use that value in the (*do_cmd).

The extra check of the cmd->convert_arg in dt282x_ai_cmd() is not necessary.
The convert_arg was already checked in the (*do_cmdtest), and it's not used
in the (*do_cmd).

Tidy up dt282x_ns_to_timer(), the parameters are all unsigned int's and the
mask of the 'flags' can be moved here to simplify the callers.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
H Hartley Sweeten 2014-06-20 13:12:59 -07:00 • committed by Greg Kroah-Hartman
commit 3ec2e20274
1 changed files with 20 additions and 21 deletions
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41
drivers/staging/comedi/drivers/dt282x.c
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@ -331,6 +331,8 @@ struct dt282x_private {
unsigned int da0_2scomp:1;
unsigned int da1_2scomp:1;
unsigned int divisor;
unsigned short ao_readback[2];
int dacsr; /* software copies of registers */
@ -413,34 +415,34 @@ static void dt282x_disable_dma(struct comedi_device *dev)
disable_dma(devpriv->dma[1].chan);
}
static int dt282x_ns_to_timer(int *nanosec, int round_mode)
static unsigned int dt282x_ns_to_timer(unsigned int *ns, unsigned int flags)
{
int prescale, base, divider;
unsigned int prescale, base, divider;
for (prescale = 0; prescale < 16; prescale++) {
if (prescale == 1)
continue;
base = 250 * (1 << prescale);
switch (round_mode) {
switch (flags & TRIG_ROUND_MASK) {
case TRIG_ROUND_NEAREST:
default:
divider = (*nanosec + base / 2) / base;
divider = (*ns + base / 2) / base;
break;
case TRIG_ROUND_DOWN:
divider = (*nanosec) / base;
divider = (*ns) / base;
break;
case TRIG_ROUND_UP:
divider = (*nanosec + base - 1) / base;
divider = (*ns + base - 1) / base;
break;
}
if (divider < 256) {
*nanosec = divider * base;
*ns = divider * base;
return (prescale << 8) | (255 - divider);
}
}
base = 250 * (1 << 15);
divider = 255;
*nanosec = divider * base;
*ns = divider * base;
return (15 << 8) | (255 - divider);
}
@ -688,9 +690,11 @@ static int dt282x_ai_insn_read(struct comedi_device *dev,
}
static int dt282x_ai_cmdtest(struct comedi_device *dev,
struct comedi_subdevice *s, struct comedi_cmd *cmd)
struct comedi_subdevice *s,
struct comedi_cmd *cmd)
{
const struct dt282x_board *board = comedi_board(dev);
struct dt282x_private *devpriv = dev->private;
int err = 0;
unsigned int arg;
@ -748,7 +752,7 @@ static int dt282x_ai_cmdtest(struct comedi_device *dev,
/* step 4: fix up any arguments */
arg = cmd->convert_arg;
dt282x_ns_to_timer(&arg, cmd->flags & TRIG_ROUND_MASK);
devpriv->divisor = dt282x_ns_to_timer(&arg, cmd->flags);
err |= cfc_check_trigger_arg_is(&cmd->convert_arg, arg);
if (err)
@ -759,18 +763,13 @@ static int dt282x_ai_cmdtest(struct comedi_device *dev,
static int dt282x_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
{
const struct dt282x_board *board = comedi_board(dev);
struct dt282x_private *devpriv = dev->private;
struct comedi_cmd *cmd = &s->async->cmd;
int timer;
int ret;
dt282x_disable_dma(dev);
if (cmd->convert_arg < board->ai_speed)
cmd->convert_arg = board->ai_speed;
timer = dt282x_ns_to_timer(&cmd->convert_arg, TRIG_ROUND_NEAREST);
outw(timer, dev->iobase + DT2821_TMRCTR);
outw(devpriv->divisor, dev->iobase + DT2821_TMRCTR);
if (cmd->scan_begin_src == TRIG_FOLLOW) {
/* internal trigger */
@ -889,8 +888,10 @@ static int dt282x_ao_insn_write(struct comedi_device *dev,
}
static int dt282x_ao_cmdtest(struct comedi_device *dev,
struct comedi_subdevice *s, struct comedi_cmd *cmd)
struct comedi_subdevice *s,
struct comedi_cmd *cmd)
{
struct dt282x_private *devpriv = dev->private;
int err = 0;
unsigned int arg;
@ -933,7 +934,7 @@ static int dt282x_ao_cmdtest(struct comedi_device *dev,
/* step 4: fix up any arguments */
arg = cmd->scan_begin_arg;
dt282x_ns_to_timer(&arg, cmd->flags & TRIG_ROUND_MASK);
devpriv->divisor = dt282x_ns_to_timer(&arg, cmd->flags);
err |= cfc_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
if (err)
@ -979,7 +980,6 @@ static int dt282x_ao_inttrig(struct comedi_device *dev,
static int dt282x_ao_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
{
struct dt282x_private *devpriv = dev->private;
int timer;
struct comedi_cmd *cmd = &s->async->cmd;
dt282x_disable_dma(dev);
@ -994,8 +994,7 @@ static int dt282x_ao_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
devpriv->dma_dir = DMA_MODE_WRITE;
devpriv->current_dma_index = 0;
timer = dt282x_ns_to_timer(&cmd->scan_begin_arg, TRIG_ROUND_NEAREST);
outw(timer, dev->iobase + DT2821_TMRCTR);
outw(devpriv->divisor, dev->iobase + DT2821_TMRCTR);
devpriv->dacsr = DT2821_SSEL | DT2821_DACLK | DT2821_IDARDY;
outw(devpriv->dacsr, dev->iobase + DT2821_DACSR);