staging: comedi: comedi_isadma: introduce helper module for ISA DMA

Introduce a new helper module to consolidate all the ISA DMA code. This will
allow removing the "depends on ISA_DMA_API" from the legacy drivers that can
use DMA for async command support.

This module is complete based on the various uses of ISA DMA in the comedi
drivers.
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/Kconfig

@@ -1262,6 +1262,9 @@ config COMEDI_DAS08
 	tristate
 	select COMEDI_8255
 
+config COMEDI_ISADMA
+	tristate
+
 config COMEDI_NI_LABPC
 	tristate
 	select COMEDI_8255

drivers/staging/comedi/drivers/Makefile

@@ -3,6 +3,7 @@
 ccflags-$(CONFIG_COMEDI_DEBUG)		:= -DDEBUG
 
 # Comedi "helper" modules
+obj-$(CONFIG_COMEDI_ISADMA)		+= comedi_isadma.o
 
 # Comedi misc drivers
 obj-$(CONFIG_COMEDI_BOND)		+= comedi_bond.o

drivers/staging/comedi/drivers/comedi_isadma.c

+/*
+ * COMEDI ISA DMA support functions
+ * Copyright (c) 2014 H Hartley Sweeten <hsweeten@visionengravers.com>
+ *
+ * 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
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <asm/dma.h>
+
+#include "../comedidev.h"
+
+#include "comedi_isadma.h"
+
+/**
+ * comedi_isadma_program - program and enable an ISA DMA transfer
+ * @desc:	the ISA DMA cookie to program and enable
+ */
+void comedi_isadma_program(struct comedi_isadma_desc *desc)
+{
+	unsigned long flags;
+
+	flags = claim_dma_lock();
+	clear_dma_ff(desc->chan);
+	set_dma_mode(desc->chan, desc->mode);
+	set_dma_addr(desc->chan, desc->hw_addr);
+	set_dma_count(desc->chan, desc->size);
+	enable_dma(desc->chan);
+	release_dma_lock(flags);
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_program);
+
+/**
+ * comedi_isadma_disable - disable the ISA DMA channel
+ * @dma_chan:	the DMA channel to disable
+ *
+ * Returns the residue (remaining bytes) left in the DMA transfer.
+ */
+unsigned int comedi_isadma_disable(unsigned int dma_chan)
+{
+	unsigned long flags;
+	unsigned int residue;
+
+	flags = claim_dma_lock();
+	disable_dma(dma_chan);
+	residue = get_dma_residue(dma_chan);
+	release_dma_lock(flags);
+
+	return residue;
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_disable);
+
+/**
+ * comedi_isadma_disable_on_sample - disable the ISA DMA channel
+ * @dma_chan:	the DMA channel to disable
+ * @size:	the sample size (in bytes)
+ *
+ * Returns the residue (remaining bytes) left in the DMA transfer.
+ */
+unsigned int comedi_isadma_disable_on_sample(unsigned int dma_chan,
+					     unsigned int size)
+{
+	int stalled = 0;
+	unsigned long flags;
+	unsigned int residue;
+	unsigned int new_residue;
+
+	residue = comedi_isadma_disable(dma_chan);
+	while (residue % size) {
+		/* residue is a partial sample, enable DMA to allow more data */
+		flags = claim_dma_lock();
+		enable_dma(dma_chan);
+		release_dma_lock(flags);
+
+		udelay(2);
+		new_residue = comedi_isadma_disable(dma_chan);
+
+		/* is DMA stalled? */
+		if (new_residue == residue) {
+			stalled++;
+			if (stalled > 10)
+				break;
+		}
+		residue = new_residue;
+		stalled = 0;
+	}
+	return residue;
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_disable_on_sample);
+
+/**
+ * comedi_isadma_poll - poll the current DMA transfer
+ * @dma:	the ISA DMA to poll
+ *
+ * Returns the position (in bytes) of the current DMA transfer.
+ */
+unsigned int comedi_isadma_poll(struct comedi_isadma *dma)
+{
+	struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
+	unsigned long flags;
+	unsigned int result;
+	unsigned int result1;
+
+	flags = claim_dma_lock();
+	clear_dma_ff(desc->chan);
+	if (!isa_dma_bridge_buggy)
+		disable_dma(desc->chan);
+	result = get_dma_residue(desc->chan);
+	/*
+	 * Read the counter again and choose higher value in order to
+	 * avoid reading during counter lower byte roll over if the
+	 * isa_dma_bridge_buggy is set.
+	 */
+	result1 = get_dma_residue(desc->chan);
+	if (!isa_dma_bridge_buggy)
+		enable_dma(desc->chan);
+	release_dma_lock(flags);
+
+	if (result < result1)
+		result = result1;
+	if (result >= desc->size || result == 0)
+		return 0;
+	else
+		return desc->size - result;
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_poll);
+
+/**
+ * comedi_isadma_set_mode - set the ISA DMA transfer direction
+ * @desc:	the ISA DMA cookie to set
+ * @dma_dir:	the DMA direction
+ */
+void comedi_isadma_set_mode(struct comedi_isadma_desc *desc, char dma_dir)
+{
+	desc->mode = (dma_dir == COMEDI_ISADMA_READ) ? DMA_MODE_READ
+						     : DMA_MODE_WRITE;
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_set_mode);
+
+/**
+ * comedi_isadma_alloc - allocate and initialize the ISA DMA
+ * @dev:	comedi_device struct
+ * @n_desc:	the number of cookies to allocate
+ * @dma_chan:	DMA channel for the first cookie
+ * @dma_chan2:	DMA channel for the second cookie
+ * @maxsize:	the size of the buffer to allocate for each cookie
+ * @dma_dir:	the DMA direction
+ *
+ * Returns the allocated and initialized ISA DMA or NULL if anything fails.
+ */
+struct comedi_isadma *comedi_isadma_alloc(struct comedi_device *dev,
+					  int n_desc, unsigned int dma_chan1,
+					  unsigned int dma_chan2,
+					  unsigned int maxsize, char dma_dir)
+{
+	struct comedi_isadma *dma = NULL;
+	struct comedi_isadma_desc *desc;
+	unsigned int dma_chans[2];
+	int i;
+
+	if (n_desc < 1 || n_desc > 2)
+		goto no_dma;
+
+	dma = kzalloc(sizeof(*dma), GFP_KERNEL);
+	if (!dma)
+		goto no_dma;
+
+	desc = kcalloc(n_desc, sizeof(*desc), GFP_KERNEL);
+	if (!desc)
+		goto no_dma;
+	dma->desc = desc;
+	dma->n_desc = n_desc;
+
+	dma_chans[0] = dma_chan1;
+	if (dma_chan2 == 0 || dma_chan2 == dma_chan1)
+		dma_chans[1] = dma_chan1;
+	else
+		dma_chans[1] = dma_chan2;
+
+	if (request_dma(dma_chans[0], dev->board_name))
+		goto no_dma;
+	dma->chan = dma_chans[0];
+	if (dma_chans[1] != dma_chans[0]) {
+		if (request_dma(dma_chans[1], dev->board_name))
+			goto no_dma;
+	}
+	dma->chan2 = dma_chans[1];
+
+	for (i = 0; i < n_desc; i++) {
+		desc = &dma->desc[i];
+		desc->chan = dma_chans[i];
+		desc->maxsize = maxsize;
+		desc->virt_addr = dma_alloc_coherent(NULL, desc->maxsize,
+						     &desc->hw_addr,
+						     GFP_KERNEL);
+		if (!desc->virt_addr)
+			goto no_dma;
+		comedi_isadma_set_mode(desc, dma_dir);
+	}
+
+	return dma;
+
+no_dma:
+	comedi_isadma_free(dma);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_alloc);
+
+/**
+ * comedi_isadma_free - free the ISA DMA
+ * @dma:	the ISA DMA to free
+ */
+void comedi_isadma_free(struct comedi_isadma *dma)
+{
+	struct comedi_isadma_desc *desc;
+	int i;
+
+	if (!dma)
+		return;
+
+	if (dma->desc) {
+		for (i = 0; i < dma->n_desc; i++) {
+			desc = &dma->desc[i];
+			if (desc->virt_addr)
+				dma_free_coherent(NULL, desc->maxsize,
+						desc->virt_addr, desc->hw_addr);
+		}
+		kfree(dma->desc);
+	}
+	if (dma->chan2 && dma->chan2 != dma->chan)
+		free_dma(dma->chan2);
+	if (dma->chan)
+		free_dma(dma->chan);
+	kfree(dma);
+}
+EXPORT_SYMBOL_GPL(comedi_isadma_free);
+
+static int __init comedi_isadma_init(void)
+{
+	return 0;
+}
+module_init(comedi_isadma_init);
+
+static void __exit comedi_isadma_exit(void)
+{
+}
+module_exit(comedi_isadma_exit);
+
+MODULE_AUTHOR("H Hartley Sweeten <hsweeten@visionengravers.com>");
+MODULE_DESCRIPTION("Comedi ISA DMA support");
+MODULE_LICENSE("GPL");

drivers/staging/comedi/drivers/comedi_isadma.h

+/*
+ * COMEDI ISA DMA support functions
+ * Copyright (c) 2014 H Hartley Sweeten <hsweeten@visionengravers.com>
+ *
+ * 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
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _COMEDI_ISADMA_H
+#define _COMEDI_ISADMA_H
+
+/*
+ * These are used to avoid issues when <asm/dma.h> and the DMA_MODE_
+ * defines are not available.
+ */
+#define COMEDI_ISADMA_READ	0
+#define COMEDI_ISADMA_WRITE	1
+
+/**
+ * struct comedi_isadma_desc - cookie for ISA DMA
+ * @virt_addr:	virtual address of buffer
+ * @hw_addr:	hardware (bus) address of buffer
+ * @chan:	DMA channel
+ * @maxsize:	allocated size of buffer (in bytes)
+ * @size:	transfer size (in bytes)
+ * @mode:	DMA_MODE_READ or DMA_MODE_WRITE
+ */
+struct comedi_isadma_desc {
+	void *virt_addr;
+	dma_addr_t hw_addr;
+	unsigned int chan;
+	unsigned int maxsize;
+	unsigned int size;
+	char mode;
+};
+
+/**
+ * struct comedi_isadma - ISA DMA data
+ * @desc:	cookie for each DMA buffer
+ * @n_desc:	the number of cookies
+ * @cur_dma:	the current cookie in use
+ * @chan:	the first DMA channel requested
+ * @chan2:	the second DMA channel requested
+ */
+struct comedi_isadma {
+	struct comedi_isadma_desc *desc;
+	int n_desc;
+	int cur_dma;
+	unsigned int chan;
+	unsigned int chan2;
+};
+
+#if IS_ENABLED(CONFIG_ISA_DMA_API)
+
+void comedi_isadma_program(struct comedi_isadma_desc *);
+unsigned int comedi_isadma_disable(unsigned int dma_chan);
+unsigned int comedi_isadma_disable_on_sample(unsigned int dma_chan,
+					     unsigned int size);
+unsigned int comedi_isadma_poll(struct comedi_isadma *);
+void comedi_isadma_set_mode(struct comedi_isadma_desc *, char dma_dir);
+
+struct comedi_isadma *comedi_isadma_alloc(struct comedi_device *,
+					  int n_desc, unsigned int dma_chan1,
+					  unsigned int dma_chan2,
+					  unsigned int maxsize, char dma_dir);
+void comedi_isadma_free(struct comedi_isadma *);
+
+#else	/* !IS_ENABLED(CONFIG_ISA_DMA_API) */
+
+static inline void comedi_isadma_program(struct comedi_isadma_desc *desc)
+{
+}
+
+static inline unsigned int comedi_isadma_disable(unsigned int dma_chan)
+{
+	return 0;
+}
+
+static inline unsigned int
+comedi_isadma_disable_on_sample(unsigned int dma_chan, unsigned int size)
+{
+	return 0;
+}
+
+static inline unsigned int comedi_isadma_poll(struct comedi_isadma *dma)
+{
+	return 0;
+}
+
+static inline void comedi_isadma_set_mode(struct comedi_isadma_desc *desc,
+					  char dma_dir)
+{
+}
+
+static inline struct comedi_isadma *
+comedi_isadma_alloc(struct comedi_device *dev, int n_desc,
+		    unsigned int dma_chan1, unsigned int dma_chan2,
+		    unsigned int maxsize, char dma_dir)
+{
+	return NULL;
+}
+
+static inline void comedi_isadma_free(struct comedi_isadma *dma)
+{
+}
+
+#endif	/* !IS_ENABLED(CONFIG_ISA_DMA_API) */
+
+#endif	/* #ifndef _COMEDI_ISADMA_H */