Commit 6aa7c167 authored by Jeff Garzik's avatar Jeff Garzik

[libata] disable clustering by default, whitespace cleanups

Disable SCSI's clustering of S/G entries, typically reducing overall
S/G list size.  Although ATA S/G tables are getting smarter (64-bit
address, 32-bit length, no DMA boundary besides 4G itself), working
harder to generate large byte sizes for each S/G size is not necessarily
in our best interest:

* SATA consists of frames, much like ethernet, called "FIS".  A
  Data FIS consists of up to 2048 dwords (8K) of data.  We don't want
  generate large byte sizes in S/G entries, just to have the host controller
  break them up again into smaller chunks.
* Reduces the possibility that ata_fill_sg (libata-core.c) must split
  an S/G into two pieces, because it straddles a 64K boundary.
* Reduces the possibility that FIS-related errata workarounds
  must be enabled.  One such exists in the Silicon Image driver (sata_sil),
  which is currently worked around by limiting the max-sectors-per-request
  to 15.
parent 585a692c
......@@ -28,7 +28,6 @@
#include <asm/io.h>
#include <linux/ata.h>
/*
* compile-time options
*/
......@@ -82,7 +81,7 @@ enum {
ATA_SHT_EMULATED = 1,
ATA_SHT_CMD_PER_LUN = 1,
ATA_SHT_THIS_ID = -1,
ATA_SHT_USE_CLUSTERING = 1,
ATA_SHT_USE_CLUSTERING = 0,
/* struct ata_device stuff */
ATA_DFLAG_LBA48 = (1 << 0), /* device supports LBA48 */
......
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