scsi: introduce a quirk for false cache reporting

Some SATA to USB bridges fail to cooperate with some
drives resulting in no cache being present being reported
to the host. That causes the host to skip sending
a command to synchronize caches. That causes data loss
when the drive is powered down.

Signed-off-by: Oliver Neukum <[e-mail]>
Reviewed-by: Martin K. Petersen <[e-mail]>
Acked-by: Alan Stern <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/kernel-parameters.txt

···
 				u = IGNORE_UAS (don't bind to the uas driver);
 				w = NO_WP_DETECT (don't test whether the
 					medium is write-protected).
+				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
+					even if the device claims no cache)
 			Example: quirks=0419:aaf5:rl,0421:0433:rc
 
 	user_debug=	[KNL,ARM]

drivers/usb/storage/scsiglue.c

···
 		if (us->fflags & US_FL_BROKEN_FUA)
 			sdev->broken_fua = 1;
 
+		/* Some even totally fail to indicate a cache */
+		if (us->fflags & US_FL_ALWAYS_SYNC) {
+			/* don't read caching information */
+			sdev->skip_ms_page_8 = 1;
+			sdev->skip_ms_page_3f = 1;
+			/* assume sync is needed */
+			sdev->wce_default_on = 1;
+		}
 	} else {
 
 		/*

drivers/usb/storage/unusual_devs.h

···
 		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
 		US_FL_NO_WP_DETECT),
 
+/* Reported by Egbert Eich <[e-mail]> */
+UNUSUAL_DEV(  0x0480, 0xd010, 0x0100, 0x9999,
+		"Toshiba",
+		"External USB 3.0",
+		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
+		US_FL_ALWAYS_SYNC),
+
 /* Patch submitted by Philipp Friedrich <[e-mail]> */
 UNUSUAL_DEV(  0x0482, 0x0100, 0x0100, 0x0100,
 		"Kyocera",

drivers/usb/storage/usb.c

···
 			US_FL_NO_READ_DISC_INFO | US_FL_NO_READ_CAPACITY_16 |
 			US_FL_INITIAL_READ10 | US_FL_WRITE_CACHE |
 			US_FL_NO_ATA_1X | US_FL_NO_REPORT_OPCODES |
-			US_FL_MAX_SECTORS_240 | US_FL_NO_REPORT_LUNS);
+			US_FL_MAX_SECTORS_240 | US_FL_NO_REPORT_LUNS |
+			US_FL_ALWAYS_SYNC);
 
 	p = quirks;
 	while (*p) {
···
 			break;
 		case 'w':
 			f |= US_FL_NO_WP_DETECT;
+			break;
+		case 'y':
+			f |= US_FL_ALWAYS_SYNC;
 			break;
 		/* Ignore unrecognized flag characters */
 		}

include/linux/usb_usual.h

···
 		/* Sets max_sectors to 240 */			\
 	US_FLAG(NO_REPORT_LUNS,	0x10000000)			\
 		/* Cannot handle REPORT_LUNS */			\
+	US_FLAG(ALWAYS_SYNC, 0x20000000)			\
+		/* lies about caching, so always sync */	\
 
 #define US_FLAG(name, value)	US_FL_##name = value ,
 enum { US_DO_ALL_FLAGS };