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Diffstat (limited to 'arch/arm/mach-sa1100/dma.c')
| -rw-r--r-- | arch/arm/mach-sa1100/dma.c | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/arch/arm/mach-sa1100/dma.c b/arch/arm/mach-sa1100/dma.c new file mode 100644 index 000000000000..be0e4427bec7 --- /dev/null +++ b/arch/arm/mach-sa1100/dma.c @@ -0,0 +1,348 @@ +/* + * 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, SA_INTERRUPT, + 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); + |