Re: [PATCH V2] PCI: rcar: Add the initialization of PCIe link in resume_noirq

From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Marek Vasut <marek.vasut@gmail.com>
Cc: linux-pci@vger.kernel.org,
	Kazufumi Ikeda <kaz-ikeda@xc.jp.nec.com>,
	Gaku Inami <gaku.inami.xw@bp.renesas.com>,
	Marek Vasut <marek.vasut+renesas@gmail.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Phil Edworthy <phil.edworthy@renesas.com>,
	Simon Horman <horms+renesas@verge.net.au>,
	Wolfram Sang <wsa@the-dreams.de>,
	linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH V2] PCI: rcar: Add the initialization of PCIe link in resume_noirq
Date: Fri, 22 Mar 2019 12:18:22 +0000	[thread overview]
Message-ID: <20190322121822.GA26257@e107981-ln.cambridge.arm.com> (raw)
In-Reply-To: <95d1076c-5490-3803-f394-9a0928c2cccb@gmail.com>

On Fri, Mar 22, 2019 at 01:09:13PM +0100, Marek Vasut wrote:
> On 3/22/19 12:31 PM, Lorenzo Pieralisi wrote:
> > On Sun, Feb 17, 2019 at 02:24:41PM +0100, marek.vasut@gmail.com wrote:
> >> From: Kazufumi Ikeda <kaz-ikeda@xc.jp.nec.com>
> >>
> >> Reestablish the PCIe link very early in the resume process in case it
> >> went down to prevent PCI accesses from hanging the bus. Such accesses
> > 
> > Hi Marek, Kazufumi,
> 
> Hi,
> 
> > Apologies for the delay.
> > 
> > Just as a clarification, when you state "in case it went down" isn't
> > this supposed to happen for every suspend cycle ? Let me know and I
> > will add a comment to the patch commit log.
> 
> It does happen on every suspend/resume cycle and if you manually put a
> remote endpoint into non-L0 state.

Ok I will update the log then.

> >> can happen early in the PCI resume process, in the resume_noirq, thus
> >> the link must be reestablished in the resume_noirq callback of the
> >> driver.
> >>
> >> Signed-off-by: Kazufumi Ikeda <kaz-ikeda@xc.jp.nec.com>
> >> Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
> >> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
> >> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> >> Cc: Phil Edworthy <phil.edworthy@renesas.com>
> >> Cc: Simon Horman <horms+renesas@verge.net.au>
> >> Cc: Wolfram Sang <wsa@the-dreams.de>
> >> Cc: linux-renesas-soc@vger.kernel.org
> > 
> > This looks like a fix (most likely fixing initial S2R support, please
> > help me chase the commit ID), should we consider it for stable kernels ?
> > 
> > Without it I understand S2R is actually broken on platforms with this
> > host bridge.
> I don't think this ever worked, so it's hard to find a Fixes: commit for
> this.

If we want to send it to stable kernels we have to select which versions
we are covering. I think the only options for a Fixes: tag are either
the initial S2R support commit for the platforms this driver runs on
or the initial driver commit that harks back to v3.16 AFAICS.

I will queue it next week so there is some time to think about it.

Thanks,
Lorenzo