scsi: ufs: core: Increase the maximum data buffer size

Measurements for one particular UFS controller + UFS device show a 25%
higher read bandwidth if the maximum data buffer size is increased from 512
KiB to 1 MiB. Hence increase the maximum size of the data buffer associated
with a single request from SCSI_DEFAULT_MAX_SECTORS (1024) * 512 bytes =
512 KiB to 1 MiB.

Notes:

 - The maximum data buffer size supported by the UFSHCI specification
   is 65535 * 256 KiB or about 16 GiB.

 - The maximum data buffer size for READ(10) commands is 65535 logical
   blocks. To transfer more than 65535 * 4096 bytes = 255 MiB with a single
   SCSI command, the READ(16) command is required. Support for READ(16) is
   optional in the UFS 3.1 and UFS 4.0 standards.

Link: https://lore.kernel.org/r/20220726225232.1362251-1-bvanassche@acm.org
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Bean Huo <beanhuo@micron.com>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Tested-by: Avri Altman <avri.altman@wdc.com>
Acked-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index f4f8ded..dbe74f6 100644 (file)
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -8304,6 +8304,7 @@ static struct scsi_host_template ufshcd_driver_template = {
        .cmd_per_lun            = UFSHCD_CMD_PER_LUN,
        .can_queue              = UFSHCD_CAN_QUEUE,
        .max_segment_size       = PRDT_DATA_BYTE_COUNT_MAX,
+       .max_sectors            = (1 << 20) / SECTOR_SIZE, /* 1 MiB */
        .max_host_blocked       = 1,
        .track_queue_depth      = 1,
        .sdev_groups            = ufshcd_driver_groups,