linux-kernel - Re: [PATCH v2 4/4] scsi: ufs: probe and init of variant driver from the platform device

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Message-ID: <CAC5umyiUYYsQpc3mzx=87it+3vgxDDT+=_Y70rwac7k1Rs3eoQ@mail.gmail.com>
Date:	Mon, 8 Jun 2015 23:47:36 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	Yaniv Gardi <ygardi@...eaurora.org>
Cc:	merez@....qualcomm.com, dovl@....qualcomm.com,
	Jej B <james.bottomley@...senpartnership.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	linux-arm-msm@...r.kernel.org, Santosh Y <santoshsy@...il.com>,
	linux-scsi-owner@...r.kernel.org,
	Subhash Jadavani <subhashj@...eaurora.org>,
	Paul Bolle <pebolle@...cali.nl>,
	Gilad Broner <gbroner@...eaurora.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Vinayak Holikatti <vinholikatti@...il.com>,
	"James E.J. Bottomley" <jbottomley@...n.com>,
	Dolev Raviv <draviv@...eaurora.org>,
	Christoph Hellwig <hch@....de>,
	Sujit Reddy Thumma <sthumma@...eaurora.org>,
	Raviv Shvili <rshvili@...eaurora.org>,
	Sahitya Tummala <stummala@...eaurora.org>,
	"open list:OPEN FIRMWARE AND..." <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] scsi: ufs: probe and init of variant driver from
 the platform device

2015-06-08 0:32 GMT+09:00  <ygardi@...eaurora.org>:
> 1)
> If ufshcd-pltfrm driver is loaded before ufs-qcom, (what actually happens
> always), then the calling to of_platform_populate() which is added,
> guarantees that ufs-qcom probe will be called and finish, before
> ufshcd_pltfrm probe continues.

I'm worrying the case ufshcd_pltfrm_probe() is called when ufshcd-pltfrm
module is installed but ufs-qcom module is _not_ installed yet, where
ufshcd-pltfrm and ufs-qcom are both built as loadable modules.

In this case, of_platform_populate() in ufshcd_pltfrm_probe() doesn't
invoke ufs-qcom probe, does it?  So I suggested using deferred probe
infrastructure by returning -EPROBE_DEFER.

> so ufs_variant device is always there, and ready.
> I think it means we are safe - since either way, we make sure ufs-qcom
> probe will be called and finish before dealing with ufs_variant device in
> ufshcd_pltfrm probe.
>
> 2) you are right. the fix added as you suggested.

Thanks for fixing it.  But a little more work is needed in v3,
I'll leave a comment to v3.
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