linux-kernel - Re: [PATCH v6 04/10] scsi: ufs: introduce UFSHCD_QUIRK_PRDT_BYTE

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Message-ID: <20200422065414.GK20318@infradead.org>
Date:   Tue, 21 Apr 2020 23:54:14 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Alim Akhtar <alim.akhtar@...sung.com>
Cc:     robh@...nel.org, devicetree@...r.kernel.org,
        linux-scsi@...r.kernel.org, krzk@...nel.org, avri.altman@....com,
        martin.petersen@...cle.com, kwmad.kim@...sung.com,
        stanley.chu@...iatek.com, cang@...eaurora.org,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 04/10] scsi: ufs: introduce
 UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk

On Fri, Apr 17, 2020 at 11:29:38PM +0530, Alim Akhtar wrote:
> Some UFS host controllers may think granularities of PRDT length and
> offset as bytes, not double words.
> 
> Signed-off-by: Kiwoong Kim <kwmad.kim@...sung.com>
> Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 30 +++++++++++++++++++++++-------
>  drivers/scsi/ufs/ufshcd.h |  6 ++++++
>  2 files changed, 29 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index ee30ed6cc805..b32fcedcdcb9 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -2151,8 +2151,14 @@ static int ufshcd_map_sg(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
>  		return sg_segments;
>  
>  	if (sg_segments) {
> -		lrbp->utr_descriptor_ptr->prd_table_length =
> -			cpu_to_le16((u16)sg_segments);
> +
> +		if (hba->quirks & UFSHCD_QUIRK_PRDT_BYTE_GRAN)
> +			lrbp->utr_descriptor_ptr->prd_table_length =
> +				cpu_to_le16((u16)(sg_segments *
> +					sizeof(struct ufshcd_sg_entry)));
> +		else
> +			lrbp->utr_descriptor_ptr->prd_table_length =
> +				cpu_to_le16((u16) (sg_segments));

No double words here.  "Normal" UFS uses the actual segment count,
while Samsumg uses bytes.  Also no need fo the u16 count in
either the old or new version.