Re: [PATCH v5 4/6] scsi: ufs: Add API to execute raw upiu commands

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On Thu, Sep 20, 2018 at 08:30:29AM +0000, Avri Altman wrote:
> > > +
> > > +	hba->dev_cmd.complete = &wait;
> > > +
> > > +	/* Make sure descriptors are ready before ringing the doorbell */
> > > +	wmb();
> > > +	spin_lock_irqsave(hba->host->host_lock, flags);
> > > +	ufshcd_send_command(hba, tag);
> > 
> > I think the above wmb() is taken care of by the writel() inside
> > ufshcd_send_command.
> Those barriers were added later (and the one in send_command() last),
> explaining that there is a need to verify that the "..descriptors are
> actually written to memory before ringing the doorbell..."

This doesn't make much sense as the rest of the kernel relies on the
fact the writel does not require a wmb().

But I guess we can keep the wmb() for now to match the rest of ufs,
and deal with this issue later.



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