[PATCH] linux-next remove wmb() from ide-dma-sff.c and scc_pata.c

[Grant Grundler]

Followup to "[PATCH 03/10] ide: destroy DMA mappings after ending DMA"
email on March 14th:
    http://lkml.org/lkml/2009/3/14/17

No maintainer is listed for "Toshiba CELL Reference Set IDE" (BLK_DEV_CELLEB)
or tx4939ide.c in MAINTAINERS. I've CC'd "Ishizaki Kou" @Toshiba (Maintainer for
"Spidernet Network Driver for CELL") and linuxppc-dev list in the hope
someone else
would know or would be able to ACK this patch.

This patch:
o replaces "mask" variable in ide_dma_end() with #define.
o removes use of wmb() in ide-dma-sff.c and scc_pata.c.
o is not tested - I don't have (or want) the HW.

I did NOT remove wmb() use in tx4939ide.c. tx4939ide.c __raw_writeb()
for MMIO transactions. __raw_writeb() does NOT guarantee memory
transaction ordering.

tx4939ide also uses mmiowb(). AFAIK, mmiowb() only has an effect on
SGI IA64 NUMA machines. I'm not going to guess how this driver might work.

Gmail is broken for sending patches (word wrap). My apologies.
I've attached the patch: diff-next-remove_wmb_from_ide-01.txt

Patch is against linux-next tree:
     git://git.kernel.org/pub/scm/linux/kernel/git/sfr/linux-next

Signed-off-by: Grant Grundler <grundler at google.com>
-------------- next part --------------
diff --git a/drivers/ide/ide-dma-sff.c b/drivers/ide/ide-dma-sff.c
index 16fc46e..e4cdf78 100644
--- a/drivers/ide/ide-dma-sff.c
+++ b/drivers/ide/ide-dma-sff.c
@@ -277,8 +277,6 @@ void ide_dma_start(ide_drive_t *drive)
 		dma_cmd = inb(hwif->dma_base + ATA_DMA_CMD);
 		outb(dma_cmd | ATA_DMA_START, hwif->dma_base + ATA_DMA_CMD);
 	}
-
-	wmb();
 }
 EXPORT_SYMBOL_GPL(ide_dma_start);
 
@@ -286,7 +284,7 @@ EXPORT_SYMBOL_GPL(ide_dma_start);
 int ide_dma_end(ide_drive_t *drive)
 {
 	ide_hwif_t *hwif = drive->hwif;
-	u8 dma_stat = 0, dma_cmd = 0, mask;
+	u8 dma_stat = 0, dma_cmd = 0;
 
 	/* stop DMA */
 	if (hwif->host_flags & IDE_HFLAG_MMIO) {
@@ -304,11 +302,10 @@ int ide_dma_end(ide_drive_t *drive)
 	/* clear INTR & ERROR bits */
 	ide_dma_sff_write_status(hwif, dma_stat | ATA_DMA_ERR | ATA_DMA_INTR);
 
-	wmb();
+#define CHECK_DMA_MASK (ATA_DMA_ACTIVE | ATA_DMA_ERR | ATA_DMA_INTR)
 
 	/* verify good DMA status */
-	mask = ATA_DMA_ACTIVE | ATA_DMA_ERR | ATA_DMA_INTR;
-	if ((dma_stat & mask) != ATA_DMA_INTR)
+	if ((dma_stat & CHECK_DMA_MASK) != ATA_DMA_INTR)
 		return 0x10 | dma_stat;
 	return 0;
 }
diff --git a/drivers/ide/scc_pata.c b/drivers/ide/scc_pata.c
index 97f8e0e..dcbb299 100644
--- a/drivers/ide/scc_pata.c
+++ b/drivers/ide/scc_pata.c
@@ -337,7 +337,6 @@ static void scc_dma_start(ide_drive_t *drive)
 
 	/* start DMA */
 	scc_ide_outb(dma_cmd | 1, hwif->dma_base);
-	wmb();
 }
 
 static int __scc_dma_end(ide_drive_t *drive)
@@ -354,7 +353,6 @@ static int __scc_dma_end(ide_drive_t *drive)
 	/* clear the INTR & ERROR bits */
 	scc_ide_outb(dma_stat | 6, hwif->dma_base + 4);
 	/* verify good DMA status */
-	wmb();
 	return (dma_stat & 7) != 4 ? (0x10 | dma_stat) : 0;
 }