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Commit 3ec2e202 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: dt282x: avoid calculating the timer divisor multiple times 



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: 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 7152f7d4

drivers/staging/comedi/drivers/dt282x.c

+20 −21
Original line number Diff line number Diff line
@@ -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);