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

Bean Huo
2021-07-27T19:36:12Z

On Tue, 2021-07-27 at 19:14 +0900, Chanho Park wrote:
> > > 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
> > Thanks for your reply.
> > so you split the "Task Tag" filed byte3 in the UPIU header to two
> > parts, bit7~bit5 is for the VHs ID, and bit4~bit0 is for the task
> > ID.
> > but this is not defined in the Spec 2.1. correct?
>
>
> You're right.
>
> For PH, TASK_TAG[7:5] will be set to "0" but a VHID will be used in
> case of VH.
>
>
>
> Best Regards,
>
> Chanho Park

Hi Chanho Park,
Thansk for yoru reply.

I didn't see your changes about task_tag and IID. Having a look at
ufshcd_prepare_utp_scsi_cmd_upiu(), the task tag in the UPIU header
is still only task tag. and IID is always 0x00.

If you didn't add these changes, your patch is un-readable, and also
the driver doesn't have a real usage case.

Also, you mentioned there is no support/change needed from the UFS
device side. But, IMO, if you changed the UPIU header, there are
changes needed on the UFS device side in order to use your driver.

Kind regards,
Bean