[SCSI] usb-storage: add support for write cache quirk

Add support for write cache quirk on usb hdd. scsi driver will be set to wce
by detecting write cache quirk in quirk list when plugging usb hdd.

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>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a92c5eb..c68634e 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2932,6 +2932,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                                        initial READ(10) command);
                                o = CAPACITY_OK (accept the capacity
                                        reported by the device);
+                               p = WRITE_CACHE (the device cache is ON
+                                       by default);
                                r = IGNORE_RESIDUE (the device reports
                                        bogus residue values);
                                s = SINGLE_LUN (the device has only one

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 11418da..a3d5436 100644 (file)
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -236,6 +236,11 @@ static int slave_configure(struct scsi_device *sdev)
                                        US_FL_SCM_MULT_TARG)) &&
                                us->protocol == USB_PR_BULK)
                        us->use_last_sector_hacks = 1;
+
+               /* Check if write cache default on flag is set or not */
+               if (us->fflags & US_FL_WRITE_CACHE)
+                       sdev->wce_default_on = 1;
+
        } else {
 
                /* Non-disk-type devices don't need to blacklist any pages

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index e23c30a..d012fe4 100644 (file)
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -473,7 +473,7 @@ static void adjust_quirks(struct us_data *us)
                        US_FL_CAPACITY_OK | US_FL_IGNORE_RESIDUE |
                        US_FL_SINGLE_LUN | US_FL_NO_WP_DETECT |
                        US_FL_NO_READ_DISC_INFO | US_FL_NO_READ_CAPACITY_16 |
-                       US_FL_INITIAL_READ10);
+                       US_FL_INITIAL_READ10 | US_FL_WRITE_CACHE);
 
        p = quirks;
        while (*p) {
@@ -529,6 +529,9 @@ static void adjust_quirks(struct us_data *us)
                case 'o':
                        f |= US_FL_CAPACITY_OK;
                        break;
+               case 'p':
+                       f |= US_FL_WRITE_CACHE;
+                       break;
                case 'r':
                        f |= US_FL_IGNORE_RESIDUE;
                        break;

diff --git a/include/linux/usb_usual.h b/include/linux/usb_usual.h
index 17df360..e84e769 100644 (file)
--- a/include/linux/usb_usual.h
+++ b/include/linux/usb_usual.h
@@ -64,7 +64,9 @@
        US_FLAG(NO_READ_CAPACITY_16,    0x00080000)             \
                /* cannot handle READ_CAPACITY_16 */            \
        US_FLAG(INITIAL_READ10, 0x00100000)                     \
-               /* Initial READ(10) (and others) must be retried */
+               /* Initial READ(10) (and others) must be retried */     \
+       US_FLAG(WRITE_CACHE,    0x00200000)                     \
+               /* Write Cache status is not available */
 
 #define US_FLAG(name, value)   US_FL_##name = value ,
 enum { US_DO_ALL_FLAGS };