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Subject: Re: [PATCH v19 3/3] scsi: ufs: Prepare HPB read for cached
 sub-region
From:   Bean Huo <huobean@gmail.com>
To:     Avri Altman <Avri.Altman@wdc.com>, Can Guo <cang@codeaurora.org>,
        "daejun7.park@samsung.com" <daejun7.park@samsung.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
        "stanley.chu@mediatek.com" <stanley.chu@mediatek.com>,
        "bvanassche@acm.org" <bvanassche@acm.org>,
        ALIM AKHTAR <alim.akhtar@samsung.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        yongmyung lee <ymhungry.lee@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        BoRam Shin <boram.shin@samsung.com>,
        SEUNGUK SHIN <seunguk.shin@samsung.com>
Date:   Fri, 05 Feb 2021 16:08:31 +0100
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On Fri, 2021-02-05 at 14:06 +0000, Avri Altman wrote:
> > > > +     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).
> 

Thanks, I tested Daejun's patchset before, it is also ok (I don't know
which version patchset). maybe we can keep current implementation as
default, then if there is conflict, and submit the quirk.

Thanks,
Bean

> Thanks,
> Avri