scsi: ufs: ufshpb: Use a correct max multi chunk

In HPB2.0, if pre_req_min_tr_len < transfer_len < pre_req_max_tr_len, the
driver is expected to send a HPB-WRITE-BUFFER companion to HPB-READ.

The upper bound should fit into a single byte, regardless of bMAX_
DATA_SIZE_FOR_HPB_SINGLE_CMD which being an attribute (u32) can be
significantly larger.

To further illustrate the issue, consider the following scenario:

 - SCSI_DEFAULT_MAX_SECTORS is 1024 limiting the I/O chunks to 512KB

 - The OEM changes scsi_host_template .max_sectors to be 2048 which allows
   for 1MB requests: transfer_len = 256

 - pre_req_max_tr_len = HPB_MULTI_CHUNK_HIGH = 256

 - ufshpb_is_supported_chunk() returns true (256 <= 256)

 - WARN_ON_ONCE(256 > 256) doesn't warn

 - ufshpb_set_hpb_read_to_upiu() casts transfer_len to u8: transfer_len = 0

 - The command is failing with ILLEGAL REQUEST

Link: https://lore.kernel.org/r/20210808090024.21721-3-avri.altman@wdc.com
Fixes: 41d8a9333cc9 (scsi: ufs: ufshpb: Add HPB 2.0 support)
Signed-off-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
index c74a6c3..6df317d 100644 (file)
--- a/drivers/scsi/ufs/ufshpb.h
+++ b/drivers/scsi/ufs/ufshpb.h
@@ -32,7 +32,7 @@
 /* hpb support chunk size */
 #define HPB_LEGACY_CHUNK_HIGH                  1
 #define HPB_MULTI_CHUNK_LOW                    7
-#define HPB_MULTI_CHUNK_HIGH                   256
+#define HPB_MULTI_CHUNK_HIGH                   255
 
 /* hpb vender defined opcode */
 #define UFSHPB_READ                            0xF8