linux-kernel - Re: [RESEND PATCH v10 04/10] scsi: ufs: introduce UFSHCD_QUIRK_PRDT_BYTE

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Date:   Wed, 12 Aug 2020 18:25:48 -0700
From:   Eric Biggers <ebiggers@...nel.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,
        kishon@...com
Subject: Re: [RESEND PATCH v10 04/10] scsi: ufs: introduce
 UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk

On Thu, Aug 13, 2020 at 06:51:13AM +0530, Alim Akhtar wrote:
> Hi Eric,
> 
> > -----Original Message-----
> > From: Eric Biggers <ebiggers@...nel.org>
> > Sent: 12 August 2020 05:59
> > 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; kishon@...com
> > Subject: Re: [RESEND PATCH v10 04/10] scsi: ufs: introduce
> > UFSHCD_QUIRK_PRDT_BYTE_GRAN quirk
> > 
> > Hi Alim,
> > 
> > On Sat, Jun 13, 2020 at 08:17:00AM +0530, Alim Akhtar wrote:
> > > Some UFS host controllers like Exynos uses granularities of PRDT
> > > length and offset as bytes, whereas others uses actual segment count.
> > >
> > > Reviewed-by: Avri Altman <avri.altman@....com>
> > > 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..ba093d0d0942 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((sg_segments *
> > > +					sizeof(struct ufshcd_sg_entry)));
> > > +		else
> > > +			lrbp->utr_descriptor_ptr->prd_table_length =
> > > +				cpu_to_le16((u16) (sg_segments));
> > >
> > >  		prd_table = (struct ufshcd_sg_entry *)lrbp->ucd_prdt_ptr;
> > >
> > > @@ -3500,11 +3506,21 @@ static void
> > ufshcd_host_memory_configure(struct ufs_hba *hba)
> > >
> > 	cpu_to_le32(upper_32_bits(cmd_desc_element_addr));
> > >
> > >  		/* Response upiu and prdt offset should be in double words
> */
> > > -		utrdlp[i].response_upiu_offset =
> > > -			cpu_to_le16(response_offset >> 2);
> > > -		utrdlp[i].prd_table_offset = cpu_to_le16(prdt_offset >> 2);
> > > -		utrdlp[i].response_upiu_length =
> > > -			cpu_to_le16(ALIGNED_UPIU_SIZE >> 2);
> > > +		if (hba->quirks & UFSHCD_QUIRK_PRDT_BYTE_GRAN) {
> > > +			utrdlp[i].response_upiu_offset =
> > > +				cpu_to_le16(response_offset);
> > > +			utrdlp[i].prd_table_offset =
> > > +				cpu_to_le16(prdt_offset);
> > > +			utrdlp[i].response_upiu_length =
> > > +				cpu_to_le16(ALIGNED_UPIU_SIZE);
> > > +		} else {
> > > +			utrdlp[i].response_upiu_offset =
> > > +				cpu_to_le16(response_offset >> 2);
> > > +			utrdlp[i].prd_table_offset =
> > > +				cpu_to_le16(prdt_offset >> 2);
> > > +			utrdlp[i].response_upiu_length =
> > > +				cpu_to_le16(ALIGNED_UPIU_SIZE >> 2);
> > > +		}
> > >
> > >  		ufshcd_init_lrb(hba, &hba->lrb[i], i);
> > >  	}
> > 
> > Isn't this patch missing an update to ufshcd_print_trs()?  It uses
> > ->prd_table_length as the number of segments, not the number of bytes.
> > 
> prd_table_length will be populated before it reaches ufshcd_print_trs()
> based on UFSHCD_QUIRK_PRDT_BYTE_GRAN.
> 

Yes, which is why it seems ufshcd_print_trs() needs to be updated to take
UFSHCD_QUIRK_PRDT_BYTE_GRAN into account.

- Eric