From b81478d82e389dd0961760f5ff6f56b50d29db6d Mon Sep 17 00:00:00 2001
From: Namjae Jeon <namjae.jeon@samsung.com>
Date: Sat, 7 Jul 2012 23:05:08 -0400
Subject: [PATCH] [SCSI] set to WCE if usb cache quirk is present.
Make use of USB quirk method to identify such HDD while reading
the cache status in sd_probe(). If cache quirk is present for
the HDD, lets assume that cache is enabled and make WCE bit
equal to 1.
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Pankaj Kumar <pankaj.km@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
---
drivers/scsi/sd.c | 9 +++++++--
include/scsi/scsi_device.h | 1 +
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 6e26db11250a5..4df73e52a4f9f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2261,8 +2261,13 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
sd_printk(KERN_ERR, sdkp, "Asking for cache data failed\n");
defaults:
- sd_printk(KERN_ERR, sdkp, "Assuming drive cache: write through\n");
- sdkp->WCE = 0;
+ if (sdp->wce_default_on) {
+ sd_printk(KERN_NOTICE, sdkp, "Assuming drive cache: write back\n");
+ sdkp->WCE = 1;
+ } else {
+ sd_printk(KERN_ERR, sdkp, "Assuming drive cache: write through\n");
+ sdkp->WCE = 0;
+ }
sdkp->RCD = 0;
sdkp->DPOFUA = 0;
}
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index bd1a14d890098..7539f52a33c9d 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -154,6 +154,7 @@ struct scsi_device {
unsigned no_read_capacity_16:1; /* Avoid READ_CAPACITY_16 cmds */
unsigned try_rc_10_first:1; /* Try READ_CAPACACITY_10 first */
unsigned is_visible:1; /* is the device visible in sysfs */
+ unsigned wce_default_on:1; /* Cache is ON by default */
DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
struct list_head event_list; /* asserted events */
--
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