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Enable multi-word DMA mode 2 for the PIIX3 chipset

PATCH New Arun Sharma 1 participant 1 message Aug 15, 2005

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Arun Sharma

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PATCH 1/1 Enable multi-word DMA mode 2 for the PIIX3 chipset

Enable multi-word DMA mode 2 for the PIIX3 chipset

Without this patch, Linux PIIX3 driver would see ultra DMA and get confused and ended up disabling DMA.

With the patch, we're able to see 3x increase in disk read throughput.

Signed-off-by Winston Wang <[email protected]>
Signed-off-by Arun Sharma <[email protected]>
tools/ioemu/hw/ide.c +2 -1
diff -r 29aab159846c -r b5196e075602 tools/ioemu/hw/ide.c
@@ -430,6 +430,7 @@
         put_le16(p + 59, 0x100 | s->mult_sectors);
     put_le16(p + 60, s->nb_sectors);
     put_le16(p + 61, s->nb_sectors >> 16);
+    put_le16(p + 63, 0x07);
     put_le16(p + 80, (1 << 1) | (1 << 2));
     put_le16(p + 82, (1 << 14));
     put_le16(p + 83, (1 << 14));

@@ -460,7 +461,7 @@
     put_le16(p + 48, 1); /* dword I/O (XXX: should not be set on CDROM) */
     put_le16(p + 49, 1 << 9); /* LBA supported, no DMA */
     put_le16(p + 53, 3); /* words 64-70, 54-58 valid */
-    put_le16(p + 63, 0x103); /* DMA modes XXX: may be incorrect */
+    put_le16(p + 63, 0x07); /* Multi-word DMA mode 2 */ 
     put_le16(p + 64, 1); /* PIO modes */
     put_le16(p + 65, 0xb4); /* minimum DMA multiword tx cycle time */
     put_le16(p + 66, 0xb4); /* recommended DMA multiword tx cycle time */