RE: [PATCH v2 14/15] scsi: ufs: ufs-exynos: multi-host configuration for exynosauto

From: "Chanho Park" <chanho61.park@samsung.com>
To: "'Bean Huo'" <huobean@gmail.com>,
	"'Krzysztof Kozlowski'" <krzk@kernel.org>,
	"'Alim Akhtar'" <alim.akhtar@samsung.com>,
	"'James E . J . Bottomley'" <jejb@linux.ibm.com>,
	"'Martin K . Petersen'" <martin.petersen@oracle.com>
Cc: "'Can Guo'" <cang@codeaurora.org>,
	"'Jaegeuk Kim'" <jaegeuk@kernel.org>,
	"'Kiwoong Kim'" <kwmad.kim@samsung.com>,
	"'Avri Altman'" <avri.altman@wdc.com>,
	"'Adrian Hunter'" <adrian.hunter@intel.com>,
	"'Christoph Hellwig'" <hch@infradead.org>,
	"'Bart Van Assche'" <bvanassche@acm.org>,
	"'jongmin jeong'" <jjmin.jeong@samsung.com>,
	"'Gyunghoon Kwon'" <goodjob.kwon@samsung.com>,
	<linux-samsung-soc@vger.kernel.org>, <linux-scsi@vger.kernel.org>
Subject: RE: [PATCH v2 14/15] scsi: ufs: ufs-exynos: multi-host configuration for exynosauto
Date: Mon, 26 Jul 2021 19:40:08 +0900	[thread overview]
Message-ID: <000601d7820a$9aa11210$cfe33630$@samsung.com> (raw)
In-Reply-To: <2b4f4e6d76cdc517843fe8880312541c754d5352.camel@gmail.com>

> > UFS controller of ExynosAuto v9 SoC supports multi-host interface for
> > I/O
> >
> > virtualization. In general, we're using para-virtualized driver to
> >
> > support a block device by several virtual machines. However, it should
> >
> > be relayed by backend driver. Multi-host functionality extends the
> > host
> >
> > controller by providing register interfaces that can be used by each
> >
> > VM's ufs drivers respectively. By this, we can provide direct access
> > to
> >
> > the UFS device for multiple VMs. It's similar with SR-IOV of PCIe.
> >
> 
> Hi Chanho Park,
> very inteseted in this patch. you mentined SR-IOV. In order to make your
> patch work on the UFS, does UFS device side need changes?
> 
> or the common current 3.1 UFS can work with this new controller?

Our UFS controller was built on top of JEDEC 2.1 spec with some custom implementations to support this feature. UFS device side, no changes will be necessary.

> 
> 
> 
> >
> >
> > We divide this M-HCI as PH(Physical Host) and VHs(Virtual Host). The
> > PH
> >
> > supports all UFSHCI functions(all SAPs) same as conventional UFSHCI
> > but
> >
> > the VH only supports data transfer function. Thus, except UTP_CMD_SAP
> > and
> >
> > UTP_TMPSAP, the PH should handle all the physical features.
> >
> >
> >
> > This patch provides an initial implementation of PH part. M-HCI can
> >
> > support up to four interfaces but this patch initially supports only
> > 1
> >
> > PH and 1 VH. For this, we uses TASK_TAG[7:5] field so TASK_TAG[4:0]
> > for
> >
> > 32 doorbel will be supported. After the PH is initiated, this will
> > send
> 
> 
> I don't understand here.  how many doorbell registers you have now?
> and doesn VHs have a doorbell register also? and each doorbell register
> still supprts 32 tags?

A PH has its own doorbell register and each VHs also has it as well.
The TASK_TAG[7:5] can be used to distinguish the origin of the request among VHs and remaining TASK_TAG[4:0] will be used for supporting 32 tags.

Best Regards,
Chanho Park