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ide: cleanup ide_build_dmatable()

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- use for_each_sg()
- move printing 'DMA table too small' message below use_pio_instead label
- merge '64KB bug' comment with function documentation
- fix intendation

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
This commit is contained in:
Bartlomiej Zolnierkiewicz 2008-10-13 21:39:47 +02:00
parent c19f7f226b
commit 14c123f371
1 changed files with 29 additions and 42 deletions
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71
drivers/ide/ide-dma.c
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@ -153,8 +153,11 @@ EXPORT_SYMBOL_GPL(ide_build_sglist);
*
* ide_build_dmatable() prepares a dma request. We map the command
* to get the pci bus addresses of the buffers and then build up
* the PRD table that the IDE layer wants to be fed. The code
* knows about the 64K wrap bug in the CS5530.
* the PRD table that the IDE layer wants to be fed.
*
* Most chipsets correctly interpret a length of 0x0000 as 64KB,
* but at least one (e.g. CS5530) misinterprets it as zero (!).
* So we break the 64KB entry into two 32KB entries instead.
*
* Returns the number of built PRD entries if all went okay,
* returns 0 otherwise.
@ -171,15 +174,12 @@ int ide_build_dmatable (ide_drive_t *drive, struct request *rq)
int i;
struct scatterlist *sg;
hwif->sg_nents = i = ide_build_sglist(drive, rq);
if (!i)
hwif->sg_nents = ide_build_sglist(drive, rq);
if (hwif->sg_nents == 0)
return 0;
sg = hwif->sg_table;
while (i) {
u32 cur_addr;
u32 cur_len;
for_each_sg(hwif->sg_table, sg, hwif->sg_nents, i) {
u32 cur_addr, cur_len, xcount, bcount;
cur_addr = sg_dma_address(sg);
cur_len = sg_dma_len(sg);
@ -191,40 +191,27 @@ int ide_build_dmatable (ide_drive_t *drive, struct request *rq)
*/
while (cur_len) {
if (count++ >= PRD_ENTRIES) {
printk(KERN_ERR "%s: DMA table too small\n", drive->name);
if (count++ >= PRD_ENTRIES)
goto use_pio_instead;
} else {
u32 xcount, bcount = 0x10000 - (cur_addr & 0xffff);
if (bcount > cur_len)
bcount = cur_len;
*table++ = cpu_to_le32(cur_addr);
xcount = bcount & 0xffff;
if (is_trm290)
xcount = ((xcount >> 2) - 1) << 16;
else if (xcount == 0x0000) {
/*
* Most chipsets correctly interpret a length of 0x0000 as 64KB,
* but at least one (e.g. CS5530) misinterprets it as zero (!).
* So here we break the 64KB entry into two 32KB entries instead.
*/
if (count++ >= PRD_ENTRIES) {
printk(KERN_ERR "%s: DMA table too small\n", drive->name);
goto use_pio_instead;
}
*table++ = cpu_to_le32(0x8000);
*table++ = cpu_to_le32(cur_addr + 0x8000);
xcount = 0x8000;
}
*table++ = cpu_to_le32(xcount);
cur_addr += bcount;
cur_len -= bcount;
bcount = 0x10000 - (cur_addr & 0xffff);
if (bcount > cur_len)
bcount = cur_len;
*table++ = cpu_to_le32(cur_addr);
xcount = bcount & 0xffff;
if (is_trm290)
xcount = ((xcount >> 2) - 1) << 16;
if (xcount == 0x0000) {
if (count++ >= PRD_ENTRIES)
goto use_pio_instead;
*table++ = cpu_to_le32(0x8000);
*table++ = cpu_to_le32(cur_addr + 0x8000);
xcount = 0x8000;
}
*table++ = cpu_to_le32(xcount);
cur_addr += bcount;
cur_len -= bcount;
}
sg = sg_next(sg);
i--;
}
if (count) {
@ -233,14 +220,14 @@ int ide_build_dmatable (ide_drive_t *drive, struct request *rq)
return count;
}
printk(KERN_ERR "%s: empty DMA table?\n", drive->name);
use_pio_instead:
printk(KERN_ERR "%s: %s\n", drive->name,
count ? "DMA table too small" : "empty DMA table?");
ide_destroy_dmatable(drive);
return 0; /* revert to PIO for this request */
}
EXPORT_SYMBOL_GPL(ide_build_dmatable);
#endif