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Subject[PATCH v4 1/3] scsi: set to WCE if usb cache quirk is present.
Date
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>
---
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 6f0a4c6..e63e363 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2259,8 +2259,13 @@ bad_sense:
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 6efb2e1..8be0247 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -152,6 +152,7 @@ struct scsi_device {
unsigned no_read_disc_info:1; /* Avoid READ_DISC_INFO cmds */
unsigned no_read_capacity_16:1; /* Avoid READ_CAPACITY_16 cmds */
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 */
--
1.7.9.5


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