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PPC: dbdma: Support unaligned DMA access 
The DBDMA engine really just reads bytes from a producing device (IDE
in our case) and shoves these bytes into memory. It doesn't care whether
any alignment takes place or not.

Our code today however assumes that block accesses always happen on
sector (512 byte) boundaries. This is a fair assumption for most cases.

However, Mac OS X really likes to do unaligned, incomplete accesses
that it finishes with the next DMA request.

So we need to read / write the unaligned bits independent of the actual
asynchronous request, because that one can only handle 512-byte-aligned
data. We also need to cache these unaligned sectors until the next DMA
request, at which point the data might be successfully flushed from the
pipe.

Signed-off-by: Alexander Graf <agraf@suse.de>
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@agraf
agraf committed Jul 11, 2013
1 parent cae3235 commit 80fc95d
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Showing 2 changed files with 127 additions and 7 deletions.
131 changes: 124 additions & 7 deletions hw/ide/macio.c
View file
Expand Up @@ -56,11 +56,13 @@ static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)
DBDMA_io *io = opaque;
MACIOIDEState *m = io->opaque;
IDEState *s = idebus_active_if(&m->bus);
int unaligned;

if (ret < 0) {
m->aiocb = NULL;
qemu_sglist_destroy(&s->sg);
ide_atapi_io_error(s, ret);
io->remainder_len = 0;
goto done;
}

Expand All @@ -85,7 +87,31 @@ static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)
s->io_buffer_index &= 0x7ff;
}

if (s->packet_transfer_size <= 0) {
s->io_buffer_size = io->len;

MACIO_DPRINTF("remainder: %d io->len: %d size: %d\n", io->remainder_len,
io->len, s->packet_transfer_size);
if (io->remainder_len && io->len) {
/* guest wants the rest of its previous transfer */
int remainder_len = MIN(io->remainder_len, io->len);

MACIO_DPRINTF("copying remainder %d bytes\n", remainder_len);

cpu_physical_memory_write(io->addr, io->remainder + 0x200 -
remainder_len, remainder_len);

io->addr += remainder_len;
io->len -= remainder_len;
s->io_buffer_size = remainder_len;
io->remainder_len -= remainder_len;
/* treat remainder as individual transfer, start again */
qemu_sglist_init(&s->sg, DEVICE(m), io->len / MACIO_PAGE_SIZE + 1,
&address_space_memory);
pmac_ide_atapi_transfer_cb(opaque, 0);
return;
}

if (!s->packet_transfer_size) {
MACIO_DPRINTF("end of transfer\n");
ide_atapi_cmd_ok(s);
m->dma_active = false;
Expand All @@ -98,14 +124,40 @@ static void pmac_ide_atapi_transfer_cb(void *opaque, int ret)

/* launch next transfer */

MACIO_DPRINTF("io->len = %#x\n", io->len);
/* handle unaligned accesses first, get them over with and only do the
remaining bulk transfer using our async DMA helpers */
unaligned = io->len & 0x1ff;
if (unaligned) {
int sector_num = (s->lba << 2) + (s->io_buffer_index >> 9);
int nsector = io->len >> 9;

s->io_buffer_size = io->len;
MACIO_DPRINTF("precopying unaligned %d bytes to %#lx\n",
unaligned, io->addr + io->len - unaligned);

bdrv_read(s->bs, sector_num + nsector, io->remainder, 1);
cpu_physical_memory_write(io->addr + io->len - unaligned,
io->remainder, unaligned);

io->len -= unaligned;
}

MACIO_DPRINTF("io->len = %#x\n", io->len);

qemu_sglist_init(&s->sg, DEVICE(m), io->len / MACIO_PAGE_SIZE + 1,
&address_space_memory);
qemu_sglist_add(&s->sg, io->addr, io->len);
io->addr += io->len;
io->addr += s->io_buffer_size;
io->remainder_len = MIN(s->packet_transfer_size - s->io_buffer_size,
(0x200 - unaligned) & 0x1ff);
MACIO_DPRINTF("set remainder to: %d\n", io->remainder_len);

/* We would read no data from the block layer, thus not get a callback.
Just fake completion manually. */
if (!io->len) {
pmac_ide_atapi_transfer_cb(opaque, 0);
return;
}

io->len = 0;

MACIO_DPRINTF("sector_num=%d size=%d, cmd_cmd=%d\n",
Expand All @@ -128,14 +180,16 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
DBDMA_io *io = opaque;
MACIOIDEState *m = io->opaque;
IDEState *s = idebus_active_if(&m->bus);
int n;
int n = 0;
int64_t sector_num;
int unaligned;

if (ret < 0) {
MACIO_DPRINTF("DMA error\n");
m->aiocb = NULL;
qemu_sglist_destroy(&s->sg);
ide_dma_error(s);
io->remainder_len = 0;
goto done;
}

Expand All @@ -158,7 +212,33 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
s->nsector -= n;
}

if (s->nsector == 0) {
MACIO_DPRINTF("remainder: %d io->len: %d nsector: %d sector_num: %ld\n",
io->remainder_len, io->len, s->nsector, sector_num);
if (io->remainder_len && io->len) {
/* guest wants the rest of its previous transfer */
int remainder_len = MIN(io->remainder_len, io->len);
uint8_t *p = &io->remainder[0x200 - remainder_len];

MACIO_DPRINTF("copying remainder %d bytes at %#lx\n",
remainder_len, io->addr);

switch (s->dma_cmd) {
case IDE_DMA_READ:
cpu_physical_memory_write(io->addr, p, remainder_len);
break;
case IDE_DMA_WRITE:
cpu_physical_memory_read(io->addr, p, remainder_len);
bdrv_write(s->bs, sector_num - 1, io->remainder, 1);
break;
case IDE_DMA_TRIM:
break;
}
io->addr += remainder_len;
io->len -= remainder_len;
io->remainder_len -= remainder_len;
}

if (s->nsector == 0 && !io->remainder_len) {
MACIO_DPRINTF("end of transfer\n");
s->status = READY_STAT | SEEK_STAT;
ide_set_irq(s->bus);
Expand All @@ -175,12 +255,49 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
s->io_buffer_index = 0;
s->io_buffer_size = io->len;

/* handle unaligned accesses first, get them over with and only do the
remaining bulk transfer using our async DMA helpers */
unaligned = io->len & 0x1ff;
if (unaligned) {
int nsector = io->len >> 9;

MACIO_DPRINTF("precopying unaligned %d bytes to %#lx\n",
unaligned, io->addr + io->len - unaligned);

switch (s->dma_cmd) {
case IDE_DMA_READ:
bdrv_read(s->bs, sector_num + nsector, io->remainder, 1);
cpu_physical_memory_write(io->addr + io->len - unaligned,
io->remainder, unaligned);
break;
case IDE_DMA_WRITE:
/* cache the contents in our io struct */
cpu_physical_memory_read(io->addr + io->len - unaligned,
io->remainder, unaligned);
break;
case IDE_DMA_TRIM:
break;
}

io->len -= unaligned;
}

MACIO_DPRINTF("io->len = %#x\n", io->len);

qemu_sglist_init(&s->sg, DEVICE(m), io->len / MACIO_PAGE_SIZE + 1,
&address_space_memory);
qemu_sglist_add(&s->sg, io->addr, io->len);
io->addr += io->len;
io->addr += io->len + unaligned;
io->remainder_len = (0x200 - unaligned) & 0x1ff;
MACIO_DPRINTF("set remainder to: %d\n", io->remainder_len);

/* We would read no data from the block layer, thus not get a callback.
Just fake completion manually. */
if (!io->len) {
pmac_ide_transfer_cb(opaque, 0);
return;
}

io->len = 0;

MACIO_DPRINTF("sector_num=%" PRId64 " n=%d, nsector=%d, cmd_cmd=%d\n",
Expand Down
3 changes: 3 additions & 0 deletions include/hw/ppc/mac_dbdma.h
View file
Expand Up @@ -39,6 +39,9 @@ struct DBDMA_io {
DBDMA_end dma_end;
/* DMA is in progress, don't start another one */
bool processing;
/* unaligned last sector of a request */
uint8_t remainder[0x200];
int remainder_len;
};

/*
Expand Down

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