/*
* arch/arm/kernel/dma-sa1100.c
*
* Support functions for the SA11x0 internal DMA channels.
*
* Copyright (C) 2000, 2001 by Nicolas Pitre
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <asm/system.h>
#include <asm/irq.h>
#include <asm/hardware.h>
#include <asm/dma.h>
#undef DEBUG
#ifdef DEBUG
#define DPRINTK( s, arg... ) printk( "dma<%p>: " s, regs , ##arg )
#else
#define DPRINTK( x... )
#endif
typedef struct {
const char *device_id; /* device name */
u_long device; /* this channel device, 0 if unused*/
dma_callback_t callback; /* to call when DMA completes */
void *data; /* ... with private data ptr */
} sa1100_dma_t;
static sa1100_dma_t dma_chan[SA1100_DMA_CHANNELS];
static spinlock_t dma_list_lock;
static irqreturn_t dma_irq_handler(int irq, void *dev_id, struct pt_regs *regs)
{
dma_regs_t *dma_regs = dev_id;
sa1100_dma_t *dma = dma_chan + (((u_int)dma_regs >> 5) & 7);
int status = dma_regs->RdDCSR;
if (status & (DCSR_ERROR)) {
printk(KERN_CRIT "DMA on \"%s\" caused an error\n", dma->device_id);
dma_regs->ClrDCSR = DCSR_ERROR;
}
dma_regs->ClrDCSR = status & (DCSR_DONEA | DCSR_DONEB);
if (dma->callback) {
if (status & DCSR_DONEA)
dma->callback(dma->data);
if (status & DCSR_DONEB)
dma->callback(dma->data);
}
return IRQ_HANDLED;
}
/**
* sa1100_request_dma - allocate one of the SA11x0's DMA chanels
* @device: The SA11x0 peripheral targeted by this request
* @device_id: An ascii name for the claiming device
* @callback: Function to be called when the DMA completes
* @data: A cookie passed back to the callback function
* @dma_regs: Pointer to the location of the allocated channel's identifier
*
* This function will search for a free DMA channel and returns the
* address of the hardware registers for that channel as the channel
* identifier. This identifier is written to the location pointed by
* @dma_regs. The list of possible values for @device are listed into
* linux/include/asm-arm/arch-sa1100/dma.h as a dma_device_t enum.
*
* Note that reading from a port and writing to the same port are
* actually considered as two different streams requiring separate
* DMA registrations.
*
* The @callback function is called from interrupt context when one
* of the two possible DMA buffers in flight has terminated. That
* function has to be small and efficient while posponing more complex
* processing to a lower priority execution context.
*
* If no channels are available, or if the desired @device is already in
* use by another DMA channel, then an error code is returned. This
* function must be called before any other DMA calls.
**/
int sa1100_request_dma (dma_device_t device, const char *device_id,
dma_callback_t callback, void *data,
dma_regs_t **dma_regs)
{
sa1100_dma_t *dma = NULL;
dma_regs_t *regs;
int i, err;
*dma_regs = NULL;
err = 0;
spin_lock(&dma_list_lock);
for (i = 0; i < SA1100_DMA_CHANNELS; i++) {
if (dma_chan[i].device == device) {
err = -EBUSY;
break;
} else if (!dma_chan[i].device && !dma) {
dma = &dma_chan[i];
}
}
if (!err) {
if (dma)
dma->device = device;
else
err = -ENOSR;
}
spin_unlock(&dma_list_lock);
if (err)
return err;
i = dma - dma_chan;
regs = (dma_regs_t *)&DDAR(i);
err = request_irq(IRQ_DMA0 + i, dma_irq_handler, IRQF_DISABLED,
device_id, regs);
if (err) {
printk(KERN_ERR
"%s: unable to request IRQ %d for %s\n",
__FUNCTION__, IRQ_DMA0 + i, device_id);
dma->device = 0;
return err;
}
*dma_regs = regs;
dma->device_id = device_id;
dma->callback = callback;
dma->data = data;
regs->ClrDCSR =
(DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
DCSR_IE | DCSR_ERROR | DCSR_RUN);
regs->DDAR = device;
return 0;
}
/**
* sa1100_free_dma - free a SA11x0 DMA channel
* @regs: identifier for the channel to free
*
* This clears all activities on a given DMA channel and releases it
* for future requests. The @regs identifier is provided by a
* successful call to sa1100_request_dma().
**/
void sa1100_free_dma(dma_regs_t *regs)
{
int i;
for (i = 0; i < SA1100_DMA_CHANNELS; i++)
if (regs == (dma_regs_t *)&DDAR(i))
break;
if (i >= SA1100_DMA_CHANNELS) {
printk(KERN_ERR "%s: bad DMA identifier\n", __FUNCTION__);
return;
}
if (!dma_chan[i].device) {
printk(KERN_ERR "%s: Trying to free free DMA\n", __FUNCTION__);
return;
}
regs->ClrDCSR =
(DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
DCSR_IE | DCSR_ERROR | DCSR_RUN);
free_irq(IRQ_DMA0 + i, regs);
dma_chan[i].device = 0;
}
/**
* sa1100_start_dma - submit a data buffer for DMA
* @regs: identifier for the channel to use
* @dma_ptr: buffer physical (or bus) start address
* @size: buffer size
*
* This function hands the given data buffer to the hardware for DMA
* access. If another buffer is already in flight then this buffer
* will be queued so the DMA engine will switch to it automatically
* when the previous one is done. The DMA engine is actually toggling
* between two buffers so at most 2 successful calls can be made before
* one of them terminates and the callback function is called.
*
* The @regs identifier is provided by a successful call to
* sa1100_request_dma().
*
* The @size must not be larger than %MAX_DMA_SIZE. If a given buffer
* is larger than that then it's the caller's responsibility to split
* it into smaller chunks and submit them separately. If this is the
* case then a @size of %CUT_DMA_SIZE is recommended to avoid ending
* up with too small chunks. The callback function can be used to chain
* submissions of buffer chunks.
*
* Error return values:
* %-EOVERFLOW: Given buffer size is too big.
* %-EBUSY: Both DMA buffers are already in use.
* %-EAGAIN: Both buffers were busy but one of them just completed
* but the interrupt handler has to execute first.
*
* This function returs 0 on success.
**/
int sa1100_start_dma(dma_regs_t *regs, dma_addr_t dma_ptr, u_int size)
{
unsigned long flags;
u_long status;
int ret;
if (dma_ptr & 3)
printk(KERN_WARNING "DMA: unaligned start address (0x%08lx)\n",
(unsigned long)dma_ptr);
if (size > MAX_DMA_SIZE)
return -EOVERFLOW;
local_irq_save(flags);
status = regs->RdDCSR;
/* If both DMA buffers are started, there's nothing else we can do. */
if ((status & (DCSR_STRTA | DCSR_STRTB)) == (DCSR_STRTA | DCSR_STRTB)) {
DPRINTK("start: st %#x busy\n", status);
ret = -EBUSY;
goto out;
}
if (((status & DCSR_BIU) && (status & DCSR_STRTB)) ||
(!(status & DCSR_BIU) && !(status & DCSR_STRTA))) {
if (status & DCSR_DONEA) {
/* give a chance for the interrupt to be processed */
ret = -EAGAIN;
goto out;
}
regs->DBSA = dma_ptr;
regs->DBTA = size;
regs->SetDCSR = DCSR_STRTA | DCSR_IE | DCSR_RUN;
DPRINTK("start a=%#x s=%d on A\n", dma_ptr, size);
} else {
if (status & DCSR_DONEB) {
/* give a chance for the interrupt to be processed */
ret = -EAGAIN;
goto out;
}
regs->DBSB = dma_ptr;
regs->DBTB = size;
regs->SetDCSR = DCSR_STRTB | DCSR_IE | DCSR_RUN;
DPRINTK("start a=%#x s=%d on B\n", dma_ptr, size);
}
ret = 0;
out:
local_irq_restore(flags);
return ret;
}
/**
* sa1100_get_dma_pos - return current DMA position
* @regs: identifier for the channel to use
*
* This function returns the current physical (or bus) address for the
* given DMA channel. If the channel is running i.e. not in a stopped
* state then the caller must disable interrupts prior calling this
* function and process the returned value before re-enabling them to
* prevent races with the completion interrupt handler and the callback
* function. The validation of the returned value is the caller's
* responsibility as well -- the hardware seems to return out of range
* values when the DMA engine completes a buffer.
*
* The @regs identifier is provided by a successful call to
* sa1100_request_dma().
**/
dma_addr_t sa1100_get_dma_pos(dma_regs_t *regs)
{
int status;
/*
* We must determine whether buffer A or B is active.
* Two possibilities: either we are in the middle of
* a buffer, or the DMA controller just switched to the
* next toggle but the interrupt hasn't been serviced yet.
* The former case is straight forward. In the later case,
* we'll do like if DMA is just at the end of the previous
* toggle since all registers haven't been reset yet.
* This goes around the edge case and since we're always
* a little behind anyways it shouldn't make a big difference.
* If DMA has been stopped prior calling this then the
* position is exact.
*/
status = regs->RdDCSR;
if ((!(status & DCSR_BIU) && (status & DCSR_STRTA)) ||
( (status & DCSR_BIU) && !(status & DCSR_STRTB)))
return regs->DBSA;
else
return regs->DBSB;
}
/**
* sa1100_reset_dma - reset a DMA channel
* @regs: identifier for the channel to use
*
* This function resets and reconfigure the given DMA channel. This is
* particularly useful after a sleep/wakeup event.
*
* The @regs identifier is provided by a successful call to
* sa1100_request_dma().
**/
void sa1100_reset_dma(dma_regs_t *regs)
{
int i;
for (i = 0; i < SA1100_DMA_CHANNELS; i++)
if (regs == (dma_regs_t *)&DDAR(i))
break;
if (i >= SA1100_DMA_CHANNELS) {
printk(KERN_ERR "%s: bad DMA identifier\n", __FUNCTION__);
return;
}
regs->ClrDCSR =
(DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
DCSR_IE | DCSR_ERROR | DCSR_RUN);
regs->DDAR = dma_chan[i].device;
}
EXPORT_SYMBOL(sa1100_request_dma);
EXPORT_SYMBOL(sa1100_free_dma);
EXPORT_SYMBOL(sa1100_start_dma);
EXPORT_SYMBOL(sa1100_get_dma_pos);
EXPORT_SYMBOL(sa1100_reset_dma);
