staging: comedi: dt2811: add async command support for AI subdevice

The interrupt support available on this board is pretty limited but its
simple enough to give basic async command support.

This allows reading a single channel continuously using either the internal
or an external clock to trigger each conversion. The command can also use
the external trigger input to start the command if the external clock is
being used for conversions.
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>

drivers/staging/comedi/drivers/dt2811.c

@@ -2,11 +2,7 @@
  * Comedi driver for Data Translation DT2811
  *
  * COMEDI - Linux Control and Measurement Device Interface
- * History:
- * Base Version  - David A. Schleef <ds@schleef.org>
- * December 1998 - Updated to work.  David does not have a DT2811
- * board any longer so this was suffering from bitrot.
- * Updated performed by ...
+ * Copyright (C) David A. Schleef <ds@schleef.org>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -28,7 +24,7 @@
  *
  * Configuration options:
  *   [0] - I/O port base address
- *   [1] - IRQ, although this is currently unused
+ *   [1] - IRQ (optional, needed for async command support)
  *   [2] - A/D reference (# of analog inputs)
  *	   0 = single-ended (16 channels)
  *	   1 = differential (8 channels)
@@ -51,6 +47,9 @@
  */
 
 #include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+
 #include "../comedidev.h"
 
 /*
@@ -61,16 +60,9 @@
 #define DT2811_ADCSR_ADERROR		BIT(6)	/* r      1=A/D error */
 #define DT2811_ADCSR_ADBUSY		BIT(5)	/* r      1=A/D busy */
 #define DT2811_ADCSR_CLRERROR		BIT(4)
-#define DT2811_ADCSR_INTENB		BIT(2)	/* r/w	  1=interupts ena */
+#define DT2811_ADCSR_DMAENB		BIT(3)	/* r/w    1=dma ena */
+#define DT2811_ADCSR_INTENB		BIT(2)	/* r/w    1=interupts ena */
 #define DT2811_ADCSR_ADMODE(x)		(((x) & 0x3) << 0)
-/* single conversion on ADGCR load */
-#define DT2811_ADCSR_ADMODE_SINGLE	DT2811_ADCSR_ADMODE(0)
-/* continuous conversion, internal clock, (clock enabled on ADGCR load) */
-#define DT2811_ADCSR_ADMODE_CONT	DT2811_ADCSR_ADMODE(1)
-/* continuous conversion, internal clock, external trigger */
-#define DT2811_ADCSR_ADMODE_EXT_TRIG	DT2811_ADCSR_ADMODE(2)
-/* continuous conversion, external clock, external trigger */
-#define DT2811_ADCSR_ADMODE_EXT		DT2811_ADCSR_ADMODE(3)
 
 #define DT2811_ADGCR_REG		0x01	/* r/w  A/D Gain/Channel */
 #define DT2811_ADGCR_GAIN(x)		(((x) & 0x3) << 6)
@@ -85,6 +77,12 @@
 #define DT2811_DI_REG			0x06	/* r   Digital Input Port 0 */
 #define DT2811_DO_REG			0x06	/* w   Digital Output Port 1 */
 
+#define DT2811_TMRCTR_REG		0x07	/* r/w  Timer/Counter */
+#define DT2811_TMRCTR_MANTISSA(x)	(((x) & 0x7) << 3)
+#define DT2811_TMRCTR_EXPONENT(x)	(((x) & 0x7) << 0)
+
+#define DT2811_OSC_BASE			1666	/* 600 kHz = 1666.6667ns */
+
 /*
  * Timer frequency control:
  *   DT2811_TMRCTR_MANTISSA	DT2811_TMRCTR_EXPONENT
@@ -98,9 +96,13 @@
  *    6      6      100 kHz	 6   1000000
  *    7     12       50 kHz	 7   10000000
  */
-#define DT2811_TMRCTR_REG		0x07	/* r/w  Timer/Counter */
-#define DT2811_TMRCTR_MANTISSA(x)	(((x) & 0x7) << 3)
-#define DT2811_TMRCTR_EXPONENT(x)	(((x) & 0x7) << 0)
+const unsigned int dt2811_clk_dividers[] = {
+	1, 10, 2, 3, 4, 5, 6, 12
+};
+
+const unsigned int dt2811_clk_multipliers[] = {
+	1, 10, 100, 1000, 10000, 100000, 1000000, 10000000
+};
 
 /*
  * The Analog Input range is set using jumpers on the board.
@@ -182,6 +184,287 @@ static const struct dt2811_board dt2811_boards[] = {
 	},
 };
 
+struct dt2811_private {
+	unsigned int ai_divisor;
+};
+
+static unsigned int dt2811_ai_read_sample(struct comedi_device *dev,
+					  struct comedi_subdevice *s)
+{
+	unsigned int val;
+
+	val = inb(dev->iobase + DT2811_ADDATA_LO_REG) |
+	      (inb(dev->iobase + DT2811_ADDATA_HI_REG) << 8);
+
+	return val & s->maxdata;
+}
+
+static irqreturn_t dt2811_interrupt(int irq, void *d)
+{
+	struct comedi_device *dev = d;
+	struct comedi_subdevice *s = dev->read_subdev;
+	struct comedi_async *async = s->async;
+	struct comedi_cmd *cmd = &async->cmd;
+	unsigned int status;
+
+	if (!dev->attached)
+		return IRQ_NONE;
+
+	status = inb(dev->iobase + DT2811_ADCSR_REG);
+
+	if (status & DT2811_ADCSR_ADERROR) {
+		async->events |= COMEDI_CB_OVERFLOW;
+
+		outb(status | DT2811_ADCSR_CLRERROR,
+		     dev->iobase + DT2811_ADCSR_REG);
+	}
+
+	if (status & DT2811_ADCSR_ADDONE) {
+		unsigned short val;
+
+		val = dt2811_ai_read_sample(dev, s);
+		comedi_buf_write_samples(s, &val, 1);
+	}
+
+	if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg)
+		async->events |= COMEDI_CB_EOA;
+
+	comedi_handle_events(dev, s);
+
+	return IRQ_HANDLED;
+}
+
+static int dt2811_ai_cancel(struct comedi_device *dev,
+			    struct comedi_subdevice *s)
+{
+	/*
+	 * Mode 0
+	 * Single conversion
+	 *
+	 * Loading a chanspec will trigger a conversion.
+	 */
+	outb(DT2811_ADCSR_ADMODE(0), dev->iobase + DT2811_ADCSR_REG);
+
+	return 0;
+}
+
+static void dt2811_ai_set_chanspec(struct comedi_device *dev,
+				   unsigned int chanspec)
+{
+	unsigned int chan = CR_CHAN(chanspec);
+	unsigned int range = CR_RANGE(chanspec);
+
+	outb(DT2811_ADGCR_CHAN(chan) | DT2811_ADGCR_GAIN(range),
+	     dev->iobase + DT2811_ADGCR_REG);
+}
+
+static int dt2811_ai_cmd(struct comedi_device *dev,
+			 struct comedi_subdevice *s)
+{
+	struct dt2811_private *devpriv = dev->private;
+	struct comedi_cmd *cmd = &s->async->cmd;
+	unsigned int mode;
+
+	if (cmd->start_src == TRIG_NOW) {
+		/*
+		 * Mode 1
+		 * Continuous conversion, internal trigger and clock
+		 *
+		 * This resets the trigger flip-flop, disabling A/D strobes.
+		 * The timer/counter register is loaded with the division
+		 * ratio which will give the required sample rate.
+		 *
+		 * Loading the first chanspec sets the trigger flip-flop,
+		 * enabling the timer/counter. A/D strobes are then generated
+		 * at the rate set by the internal clock/divider.
+		 */
+		mode = DT2811_ADCSR_ADMODE(1);
+	} else { /* TRIG_EXT */
+		if (cmd->convert_src == TRIG_TIMER) {
+			/*
+			 * Mode 2
+			 * Continuous conversion, external trigger
+			 *
+			 * Similar to Mode 1, with the exception that the
+			 * trigger flip-flop must be set by a negative edge
+			 * on the external trigger input.
+			 */
+			mode = DT2811_ADCSR_ADMODE(2);
+		} else { /* TRIG_EXT */
+			/*
+			 * Mode 3
+			 * Continuous conversion, external trigger, clock
+			 *
+			 * Similar to Mode 2, with the exception that the
+			 * conversion rate is set by the frequency on the
+			 * external clock/divider.
+			 */
+			mode = DT2811_ADCSR_ADMODE(3);
+		}
+	}
+	outb(mode | DT2811_ADCSR_INTENB, dev->iobase + DT2811_ADCSR_REG);
+
+	/* load timer */
+	outb(devpriv->ai_divisor, dev->iobase + DT2811_TMRCTR_REG);
+
+	/* load chanspec - enables timer */
+	dt2811_ai_set_chanspec(dev, cmd->chanlist[0]);
+
+	return 0;
+}
+
+static unsigned int dt2811_ns_to_timer(unsigned int *nanosec,
+				       unsigned int flags)
+{
+	unsigned long long ns = *nanosec;
+	unsigned int ns_lo = COMEDI_MIN_SPEED;
+	unsigned int ns_hi = 0;
+	unsigned int divisor_hi = 0;
+	unsigned int divisor_lo = 0;
+	unsigned int _div;
+	unsigned int _mult;
+
+	/*
+	 * Work through all the divider/multiplier values to find the two
+	 * closest divisors to generate the requested nanosecond timing.
+	 */
+	for (_div = 0; _div <= 7; _div++) {
+		for (_mult = 0; _mult <= 7; _mult++) {
+			unsigned int div = dt2811_clk_dividers[_div];
+			unsigned int mult = dt2811_clk_multipliers[_mult];
+			unsigned long long divider = div * mult;
+			unsigned int divisor = DT2811_TMRCTR_MANTISSA(_div) |
+					       DT2811_TMRCTR_EXPONENT(_mult);
+
+			/*
+			 * The timer can be configured to run at a slowest
+			 * speed of 0.005hz (600 Khz/120000000), which requires
+			 * 37-bits to represent the nanosecond value. Limit the
+			 * slowest timing to what comedi handles (32-bits).
+			 */
+			ns = divider * DT2811_OSC_BASE;
+			if (ns > COMEDI_MIN_SPEED)
+				continue;
+
+			/* Check for fastest found timing */
+			if (ns <= *nanosec && ns > ns_hi) {
+				ns_hi = ns;
+				divisor_hi = divisor;
+			}
+			/* Check for slowest found timing */
+			if (ns >= *nanosec && ns < ns_lo) {
+				ns_lo = ns;
+				divisor_lo = divisor;
+			}
+		}
+	}
+
+	/*
+	 * The slowest found timing will be invalid if the requested timing
+	 * is faster than what can be generated by the timer. Fix it so that
+	 * CMDF_ROUND_UP returns valid timing.
+	 */
+	if (ns_lo == COMEDI_MIN_SPEED) {
+		ns_lo = ns_hi;
+		divisor_lo = divisor_hi;
+	}
+	/*
+	 * The fastest found timing will be invalid if the requested timing
+	 * is less than what can be generated by the timer. Fix it so that
+	 * CMDF_ROUND_NEAREST and CMDF_ROUND_DOWN return valid timing.
+	 */
+	if (ns_hi == 0) {
+		ns_hi = ns_lo;
+		divisor_hi = divisor_lo;
+	}
+
+	switch (flags & CMDF_ROUND_MASK) {
+	case CMDF_ROUND_NEAREST:
+	default:
+		if (ns_hi - *nanosec < *nanosec - ns_lo) {
+			*nanosec = ns_lo;
+			return divisor_lo;
+		}
+		*nanosec = ns_hi;
+		return divisor_hi;
+	case CMDF_ROUND_UP:
+		*nanosec = ns_lo;
+		return divisor_lo;
+	case CMDF_ROUND_DOWN:
+		*nanosec = ns_hi;
+		return divisor_hi;
+	}
+}
+
+static int dt2811_ai_cmdtest(struct comedi_device *dev,
+			     struct comedi_subdevice *s,
+			     struct comedi_cmd *cmd)
+{
+	struct dt2811_private *devpriv = dev->private;
+	unsigned int arg;
+	int err = 0;
+
+	/* Step 1 : check if triggers are trivially valid */
+
+	err |= comedi_check_trigger_src(&cmd->start_src, TRIG_NOW | TRIG_EXT);
+	err |= comedi_check_trigger_src(&cmd->scan_begin_src, TRIG_FOLLOW);
+	err |= comedi_check_trigger_src(&cmd->convert_src,
+					TRIG_TIMER | TRIG_EXT);
+	err |= comedi_check_trigger_src(&cmd->scan_end_src, TRIG_COUNT);
+	err |= comedi_check_trigger_src(&cmd->stop_src, TRIG_COUNT | TRIG_NONE);
+
+	if (err)
+		return 1;
+
+	/* Step 2a : make sure trigger sources are unique */
+
+	err |= comedi_check_trigger_is_unique(cmd->start_src);
+	err |= comedi_check_trigger_is_unique(cmd->convert_src);
+	err |= comedi_check_trigger_is_unique(cmd->stop_src);
+
+	/* Step 2b : and mutually compatible */
+
+	if (cmd->convert_src == TRIG_EXT && cmd->start_src != TRIG_EXT)
+		err |= -EINVAL;
+
+	if (err)
+		return 2;
+
+	/* Step 3: check if arguments are trivially valid */
+
+	err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);
+	err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, 0);
+	if (cmd->convert_src == TRIG_TIMER)
+		err |= comedi_check_trigger_arg_min(&cmd->convert_arg, 12500);
+	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
+					   cmd->chanlist_len);
+	if (cmd->stop_src == TRIG_COUNT)
+		err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
+	else	/* TRIG_NONE */
+		err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);
+
+	if (err)
+		return 3;
+
+	/* Step 4: fix up any arguments */
+
+	if (cmd->convert_src == TRIG_TIMER) {
+		arg = cmd->convert_arg;
+		devpriv->ai_divisor = dt2811_ns_to_timer(&arg, cmd->flags);
+		err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg);
+	} else { /* TRIG_EXT */
+		/* The convert_arg is used to set the divisor. */
+		devpriv->ai_divisor = cmd->convert_arg;
+	}
+
+	if (err)
+		return 4;
+
+	/* Step 5: check channel list if it exists */
+
+	return 0;
+}
+
 static int dt2811_ai_eoc(struct comedi_device *dev,
 			 struct comedi_subdevice *s,
 			 struct comedi_insn *insn,
@@ -200,30 +483,22 @@ static int dt2811_ai_insn_read(struct comedi_device *dev,
 			       struct comedi_insn *insn,
 			       unsigned int *data)
 {
-	unsigned int chan = CR_CHAN(insn->chanspec);
-	unsigned int range = CR_RANGE(insn->chanspec);
 	int ret;
 	int i;
 
+	/* We will already be in Mode 0 */
 	for (i = 0; i < insn->n; i++) {
-		unsigned int val;
-
-		/* select channel/gain and trigger conversion */
-		outb(DT2811_ADGCR_CHAN(chan) | DT2811_ADGCR_GAIN(range),
-		     dev->iobase + DT2811_ADGCR_REG);
+		/* load chanspec and trigger conversion */
+		dt2811_ai_set_chanspec(dev, insn->chanspec);
 
 		ret = comedi_timeout(dev, s, insn, dt2811_ai_eoc, 0);
 		if (ret)
 			return ret;
 
-		val = inb(dev->iobase + DT2811_ADDATA_LO_REG) |
-		      (inb(dev->iobase + DT2811_ADDATA_HI_REG) << 8);
-		val &= s->maxdata;
-
-		data[i] = val;
+		data[i] = dt2811_ai_read_sample(dev, s);
 	}
 
-	return i;
+	return insn->n;
 }
 
 static int dt2811_ao_insn_write(struct comedi_device *dev,
@@ -269,16 +544,42 @@ static int dt2811_do_insn_bits(struct comedi_device *dev,
 	return insn->n;
 }
 
+static void dt2811_reset(struct comedi_device *dev)
+{
+	/* This is the initialization sequence from the users manual */
+	outb(DT2811_ADCSR_ADMODE(0), dev->iobase + DT2811_ADCSR_REG);
+	usleep_range(100, 1000);
+	inb(dev->iobase + DT2811_ADDATA_LO_REG);
+	inb(dev->iobase + DT2811_ADDATA_HI_REG);
+	outb(DT2811_ADCSR_ADMODE(0) | DT2811_ADCSR_CLRERROR,
+	     dev->iobase + DT2811_ADCSR_REG);
+}
+
 static int dt2811_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 {
 	const struct dt2811_board *board = dev->board_ptr;
+	struct dt2811_private *devpriv;
 	struct comedi_subdevice *s;
 	int ret;
 
+	devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
+	if (!devpriv)
+		return -ENOMEM;
+
 	ret = comedi_request_region(dev, it->options[0], 0x8);
 	if (ret)
 		return ret;
 
+	dt2811_reset(dev);
+
+	/* IRQ's 2,3,5,7 are valid for async command support */
+	if (it->options[1] <= 7  && (BIT(it->options[1]) & 0xac)) {
+		ret = request_irq(it->options[1], dt2811_interrupt, 0,
+				  dev->board_name, dev);
+		if (ret == 0)
+			dev->irq = it->options[1];
+	}
+
 	ret = comedi_alloc_subdevices(dev, 4);
 	if (ret)
 		return ret;
@@ -294,6 +595,14 @@ static int dt2811_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	s->range_table	= board->is_pgh ? &dt2811_pgh_ai_ranges
 					: &dt2811_pgl_ai_ranges;
 	s->insn_read	= dt2811_ai_insn_read;
+	if (dev->irq) {
+		dev->read_subdev = s;
+		s->subdev_flags	|= SDF_CMD_READ;
+		s->len_chanlist	= 1;
+		s->do_cmdtest	= dt2811_ai_cmdtest;
+		s->do_cmd	= dt2811_ai_cmd;
+		s->cancel	= dt2811_ai_cancel;
+	}
 
 	/* Analog Output subdevice */
 	s = &dev->subdevices[1];