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

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Message-ID: <DM6PR04MB6575C8C5BEE5BCDA7EBE786BFC8E9@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Tue, 9 Feb 2021 13:25:35 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Avri Altman <Avri.Altman@....com>, Bean Huo <huobean@...il.com>,
        Can Guo <cang@...eaurora.org>,
        "daejun7.park@...sung.com" <daejun7.park@...sung.com>
CC:     Greg KH <gregkh@...uxfoundation.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "bvanassche@....org" <bvanassche@....org>,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...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

> 
> 
> > > > +     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?
> I don't know.  Better let Daejun answer this.
> This was working for me for both Galaxy S20 (Exynos) as well as Xiaomi Mi10
> (8250).
As for the endianity issue - 
I don't think that any fix is needed in the hpb driver.
It is readily seen that the ppn from get_ppn, and the one in the upiu cdb (upiu trace) are identical.
Therefore, if an issue exist, it is IMHO a device issue.

kworker/u16:10-315   [001] d..2    62.283264: ufshpb_get_ppn: Avri ppn 480d2f8244c21abd
  kworker/u16:10-315   [001] d..2    62.283336: ufshcd_upiu: v:1.10 send: T:62283314922, HDR:014000000000000000000000, CDB:8800002ddaac480d2f8244c21abd0100, D:

Again, verified on both gs20 (exynos) and mi10 (8250).
Thanks,
Avri