[PATCH 0/2] scsi: ufs: Two minor optimizations in query UPIU preparation

[PATCH 0/2] scsi: ufs: Two minor optimizations in query UPIU preparation

[Avri Altman]

This short series introduces two minor optimizations to the UPIU
preparation code in the UFS core driver. Shouldn't have functional
impact.

Avri Altman (2):
  scsi: ufs: Clear ucd_rsp_ptr for UPIU requests once
  scsi: ufs: Document NOP_OUT transaction code

 drivers/ufs/core/ufshcd.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

-- 
2.25.1

[PATCH 1/2] scsi: ufs: Clear ucd_rsp_ptr for UPIU requests once

[Avri Altman]

Previously, the response buffer (ucd_rsp_ptr) was cleared in multiple
UPIU preparation functions. Do it once.

Signed-off-by: Avri Altman <avri.altman@sandisk.com>
---
 drivers/ufs/core/ufshcd.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 0a702356a715..c2048aca09fc 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -2826,8 +2826,6 @@ static void ufshcd_prepare_utp_query_req_upiu(struct ufs_hba *hba,
 	/* Copy the Descriptor */
 	if (query->request.upiu_req.opcode == UPIU_QUERY_OPCODE_WRITE_DESC)
 		memcpy(ucd_req_ptr + 1, query->descriptor, len);
-
-	memset(lrbp->ucd_rsp_ptr, 0, sizeof(struct utp_upiu_rsp));
 }
 
 static inline void ufshcd_prepare_utp_nop_upiu(struct ufshcd_lrb *lrbp)
@@ -2840,8 +2838,6 @@ static inline void ufshcd_prepare_utp_nop_upiu(struct ufshcd_lrb *lrbp)
 		.transaction_code = UPIU_TRANSACTION_NOP_OUT,
 		.task_tag = lrbp->task_tag,
 	};
-
-	memset(lrbp->ucd_rsp_ptr, 0, sizeof(struct utp_upiu_rsp));
 }
 
 /**
@@ -2867,6 +2863,8 @@ static int ufshcd_compose_devman_upiu(struct ufs_hba *hba,
 	else
 		ret = -EINVAL;
 
+	memset(lrbp->ucd_rsp_ptr, 0, sizeof(struct utp_upiu_rsp));
+
 	return ret;
 }
 
-- 
2.25.1

[PATCH 2/2] scsi: ufs: Document NOP_OUT transaction code

[Avri Altman]

UPIU_TRANSACTION_NOP_OUT is 0x0, which is the default value after
memset. Comment out the explicit assignment and leave it as
documentation.

Signed-off-by: Avri Altman <avri.altman@sandisk.com>
---
 drivers/ufs/core/ufshcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index c2048aca09fc..84165b45467d 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -2835,7 +2835,7 @@ static inline void ufshcd_prepare_utp_nop_upiu(struct ufshcd_lrb *lrbp)
 	memset(ucd_req_ptr, 0, sizeof(struct utp_upiu_req));
 
 	ucd_req_ptr->header = (struct utp_upiu_header){
-		.transaction_code = UPIU_TRANSACTION_NOP_OUT,
+		/* .transaction_code = UPIU_TRANSACTION_NOP_OUT = 0x0, */
 		.task_tag = lrbp->task_tag,
 	};
 }
-- 
2.25.1

Re: [PATCH 2/2] scsi: ufs: Document NOP_OUT transaction code

[Bart Van Assche]

On 6/17/25 2:56 AM, Avri Altman wrote:
> UPIU_TRANSACTION_NOP_OUT is 0x0, which is the default value after
> memset. Comment out the explicit assignment and leave it as
> documentation.

This description is based on the assumption that the compiler only
initializes the data structure members that have been mentioned 
explicitly. That is wrong. There is no partial initialization in the
C programming language. Structure members that have not been mentioned
explicitly are zero-initialized. All structure members, including those
that have not been mentioned explicitly, are copied when performing
structure assignment.

> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index c2048aca09fc..84165b45467d 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -2835,7 +2835,7 @@ static inline void ufshcd_prepare_utp_nop_upiu(struct ufshcd_lrb *lrbp)
>   	memset(ucd_req_ptr, 0, sizeof(struct utp_upiu_req));
>   
>   	ucd_req_ptr->header = (struct utp_upiu_header){
> -		.transaction_code = UPIU_TRANSACTION_NOP_OUT,
> +		/* .transaction_code = UPIU_TRANSACTION_NOP_OUT = 0x0, */
>   		.task_tag = lrbp->task_tag,
>   	};
>   }

This patch probably doesn't change the generated assembly code. So I
don't think that it is useful.

Bart.

Re: [PATCH 1/2] scsi: ufs: Clear ucd_rsp_ptr for UPIU requests once

[Bart Van Assche]

On 6/17/25 2:56 AM, Avri Altman wrote:
> Previously, the response buffer (ucd_rsp_ptr) was cleared in multiple
> UPIU preparation functions. Do it once.
> 
> Signed-off-by: Avri Altman <avri.altman@sandisk.com>
> ---
>   drivers/ufs/core/ufshcd.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 0a702356a715..c2048aca09fc 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -2826,8 +2826,6 @@ static void ufshcd_prepare_utp_query_req_upiu(struct ufs_hba *hba,
>   	/* Copy the Descriptor */
>   	if (query->request.upiu_req.opcode == UPIU_QUERY_OPCODE_WRITE_DESC)
>   		memcpy(ucd_req_ptr + 1, query->descriptor, len);
> -
> -	memset(lrbp->ucd_rsp_ptr, 0, sizeof(struct utp_upiu_rsp));
>   }
>   
>   static inline void ufshcd_prepare_utp_nop_upiu(struct ufshcd_lrb *lrbp)
> @@ -2840,8 +2838,6 @@ static inline void ufshcd_prepare_utp_nop_upiu(struct ufshcd_lrb *lrbp)
>   		.transaction_code = UPIU_TRANSACTION_NOP_OUT,
>   		.task_tag = lrbp->task_tag,
>   	};
> -
> -	memset(lrbp->ucd_rsp_ptr, 0, sizeof(struct utp_upiu_rsp));
>   }
>   
>   /**
> @@ -2867,6 +2863,8 @@ static int ufshcd_compose_devman_upiu(struct ufs_hba *hba,
>   	else
>   		ret = -EINVAL;
>   
> +	memset(lrbp->ucd_rsp_ptr, 0, sizeof(struct utp_upiu_rsp));
> +
>   	return ret;
>   }

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH 1/2] scsi: ufs: Clear ucd_rsp_ptr for UPIU requests once

[Martin K. Petersen]

Avri,

> Previously, the response buffer (ucd_rsp_ptr) was cleared in multiple
> UPIU preparation functions. Do it once.

Applied to 6.17/scsi-staging, thanks!

-- 
Martin K. Petersen

Re: (subset) [PATCH 0/2] scsi: ufs: Two minor optimizations in query UPIU preparation

[Martin K. Petersen]

On Tue, 17 Jun 2025 12:56:09 +0300, Avri Altman wrote:

> This short series introduces two minor optimizations to the UPIU
> preparation code in the UFS core driver. Shouldn't have functional
> impact.
> 
> Avri Altman (2):
>   scsi: ufs: Clear ucd_rsp_ptr for UPIU requests once
>   scsi: ufs: Document NOP_OUT transaction code
> 
> [...]

Applied to 6.17/scsi-queue, thanks!

[1/2] scsi: ufs: Clear ucd_rsp_ptr for UPIU requests once
      https://git.kernel.org/mkp/scsi/c/d56d980d9b28

-- 
Martin K. Petersen	Oracle Linux Engineering