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: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/dt282x.c b/drivers/staging/comedi/drivers/dt282x.c
index 28ee5a3c3f14f4c42485b1ab1cc3ae372b40d1fd..9d8b603cdf687600d03269c936ebd8684dd1b430 100644 (file)
--- a/drivers/staging/comedi/drivers/dt282x.c
+++ b/drivers/staging/comedi/drivers/dt282x.c
@@ -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);