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

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Message-ID: <8c79dfb0dc749c3c1362b57c5a9766c0@codeaurora.org>
Date:   Mon, 08 Feb 2021 17:58:47 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Bean Huo <huobean@...il.com>
Cc:     daejun7.park@...sung.com, 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 2021-02-08 16:16, Bean Huo wrote:
> On Fri, 2021-02-05 at 11:29 +0800, Can Guo wrote:
>> > +     return ppn_table[offset];
>> > +}
>> > +
>> > +static void
>> > +ufshpb_get_pos_from_lpn(struct ufshpb_lu *hpb, unsigned long lpn,
>> > int
>> > *rgn_idx,
>> > +                     int *srgn_idx, int *offset)
>> > +{
>> > +     int rgn_offset;
>> > +
>> > +     *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.
>> 
> 
> 
> Actaully, here uses put_unaligned_be64 is no problem. SCSI command
> should be big-endian filled. I Think the problem is that geting ppn
> from HPB cache in ufshpb_get_ppn().
> 

whatever...

> ...
> e0000001f: 12 34 56 78 90 fa de ef
> ...
> 
> +
> +static u64 ufshpb_get_ppn(struct ufshpb_lu *hpb,
> +			  struct ufshpb_map_ctx *mctx, int pos, int
> *error)
> +{
> +	u64 *ppn_table;  // It s a 64 bits pointer
> +	struct page *page;
> +	int index, offset;
> +
> +	index = pos / (PAGE_SIZE / HPB_ENTRY_SIZE);
> +	offset = pos % (PAGE_SIZE / HPB_ENTRY_SIZE);
> +
> +	page = mctx->m_page[index];
> +	if (unlikely(!page)) {
> +		*error = -ENOMEM;
> +		dev_err(&hpb->sdev_ufs_lu->sdev_dev,
> +			"error. cannot find page in mctx\n");
> +		return 0;
> +	}
> +
> +	ppn_table = page_address(page);
> +	if (unlikely(!ppn_table)) {
> +		*error = -ENOMEM;
> +		dev_err(&hpb->sdev_ufs_lu->sdev_dev,
> +			"error. cannot get ppn_table\n");
> +		return 0;
> +	}
> +
> +	return ppn_table[offset];
> +}
> 
> 
> 
> 
>> 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.
>> Actually, I have seen at least two flash vendors acting so. I had to
>> modify this line
>> to get the code work properly on my setups.
>> 
>> Meanwhile, in your cover letter, you mentioned that the performance
>> data
>> is collected
>> on a UFS2.1 device. Please re-collect the data on a real UFS3.1
>> device
>> and let me
>> know the part number. Otherwise, the data is not quite convincing to
>> us.
>> 
>> Regards,
>> Can Guo.