[PATCH 2/4] scsi: ufshpb: Use a correct max multi chunk

From: Avri Altman
Date: Sun Aug 08 2021 - 05:01:20 EST


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 let us consider the following scenario:
- SCSI_DEFAULT_MAX_SECTORS is 1024 limiting the IO chunks to 512KB
- The OEM changes scsi_host_template .max_sectors to be 2048, which
allows a 1M 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 cast transfer_len to u8: transfer_len = 0
- the command is failing with illegal request

Fixes: 41d8a9333cc9 (scsi: ufs: ufshpb: Add HPB 2.0 support)
Signed-off-by: Avri Altman <avri.altman@xxxxxxx>
---
drivers/scsi/ufs/ufshpb.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
index c74a6c35a446..6df317dfe034 100644
--- 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
--
2.17.1