linux-kernel - Re: [PATCH v2] scsi: ufs: Use pre-calculated offsets in ufshcd_init

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Message-ID: <5c15b6c8-b47b-40fc-ba05-e71ef6681ad2@acm.org>
Date: Tue, 17 Sep 2024 11:21:39 -0700
From: Bart Van Assche <bvanassche@....org>
To: Avri Altman <avri.altman@....com>,
 "Martin K . Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org, Alim Akhtar <alim.akhtar@...sung.com>
Subject: Re: [PATCH v2] scsi: ufs: Use pre-calculated offsets in
 ufshcd_init_lrb

On 9/9/24 9:45 PM, Avri Altman wrote:
> Replace manual offset calculations for response_upiu and prd_table in
> ufshcd_init_lrb() with pre-calculated offsets already stored in the
> utp_transfer_req_desc structure. The pre-calculated offsets are set
> differently in ufshcd_host_memory_configure() based on the
> UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk, ensuring correct alignment and
> access.
> 
> Fixes: 26f968d7de82 ("scsi: ufs: Introduce UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk")
> Cc: stable@...r.kernel.org
> Signed-off-by: Avri Altman <avri.altman@....com>
> 
> ---
> Changes in v2:
>   - add Fixes: and Cc: stable tags
>   - fix kernel test robot warning about type mismatch by using le16_to_cpu
> ---
>   drivers/ufs/core/ufshcd.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 8ea5a82503a9..85251c176ef7 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -2919,9 +2919,8 @@ static void ufshcd_init_lrb(struct ufs_hba *hba, struct ufshcd_lrb *lrb, int i)
>   	struct utp_transfer_req_desc *utrdlp = hba->utrdl_base_addr;
>   	dma_addr_t cmd_desc_element_addr = hba->ucdl_dma_addr +
>   		i * ufshcd_get_ucd_size(hba);
> -	u16 response_offset = offsetof(struct utp_transfer_cmd_desc,
> -				       response_upiu);
> -	u16 prdt_offset = offsetof(struct utp_transfer_cmd_desc, prd_table);
> +	u16 response_offset = le16_to_cpu(utrdlp[i].response_upiu_offset);
> +	u16 prdt_offset = le16_to_cpu(utrdlp[i].prd_table_offset);
>   
>   	lrb->utr_descriptor_ptr = utrdlp + i;
>   	lrb->utrd_dma_addr = hba->utrdl_dma_addr +

Please always Cc the author of the original patch when posting a
candidate fix.

Alim, since the upstream kernel code seems to work fine with Exynos UFS
host controllers, is the description of UFSHCD_QUIRK_PRDT_BYTE_GRAN
perhaps wrong? I'm referring to the following description:

	/*
	 * This quirk needs to be enabled if the host controller regards
	 * resolution of the values of PRDTO and PRDTL in UTRD as byte.
	 */
	UFSHCD_QUIRK_PRDT_BYTE_GRAN			= 1 << 9,

Thanks,

Bart.