linux-kernel - Re: [PATCH v19 3/3] scsi: ufs: Prepare HPB read for cached sub-region

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Message-ID: <b6a8652c00411e3f71d33e7a6322f49eb5701039.camel@gmail.com>
Date:   Fri, 05 Feb 2021 13:35:13 +0100
From:   Bean Huo <huobean@...il.com>
To:     Can Guo <cang@...eaurora.org>, daejun7.park@...sung.com
Cc:     Greg KH <gregkh@...uxfoundation.org>, avri.altman@....com,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        asutoshd@...eaurora.org, stanley.chu@...iatek.com,
        bvanassche@....org, ALIM AKHTAR <alim.akhtar@...sung.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sung-Jun Park <sungjun07.park@...sung.com>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>,
        BoRam Shin <boram.shin@...sung.com>,
        SEUNGUK SHIN <seunguk.shin@...sung.com>
Subject: Re: [PATCH v19 3/3] scsi: ufs: Prepare HPB read for cached
 sub-region

On Fri, 2021-02-05 at 11:29 +0800, Can Guo wrote:
> > +     *rgn_idx = lpn >> hpb->entries_per_rgn_shift;
> > +     rgn_offset = lpn & hpb->entries_per_rgn_mask;
> > +     *srgn_idx = rgn_offset >> hpb->entries_per_srgn_shift;
> > +     *offset = rgn_offset & hpb->entries_per_srgn_mask;
> > +}
> > +
> > +static void
> > +ufshpb_set_hpb_read_to_upiu(struct ufshpb_lu *hpb, struct
> > ufshcd_lrb 
> > *lrbp,
> > +                               u32 lpn, u64 ppn,  unsigned int
> > transfer_len)
> > +{
> > +     unsigned char *cdb = lrbp->cmd->cmnd;
> > +
> > +     cdb[0] = UFSHPB_READ;
> > +
> > +     put_unaligned_be64(ppn, &cdb[6]);
> 
> You are assuming the HPB entries read out by "HPB Read Buffer" cmd
> are 
> in Little
> Endian, which is why you are using put_unaligned_be64 here. However, 
> this assumption
> is not right for all the other flash vendors - HPB entries read out
> by 
> "HPB Read Buffer"
> cmd may come in Big Endian, if so, their random read performance are 
> screwed.

For this question, it is very hard to make a correct format since the
Spec doesn't give a clear definition. Should we have a default format,
if there is conflict, and then add quirk or add a vendor-specific
table?

Hi Avri
Do you have a good idea?

Bean