linux-kernel - Re: [PATCH v3 00/15] Bring suspend to RAM support to PCIe Aardvark driver

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Message-ID: <20190125124011.GA16389@e107981-ln.cambridge.arm.com>
Date:   Fri, 25 Jan 2019 12:40:11 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Gregory Clement <gregory.clement@...tlin.com>,
        Jason Cooper <jason@...edaemon.net>,
        Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Nadav Haklai <nadavh@...vell.com>
Subject: Re: [PATCH v3 00/15] Bring suspend to RAM support to PCIe Aardvark
 driver

On Fri, Jan 25, 2019 at 11:05:30AM +0100, Miquel Raynal wrote:
> Hi Lorenzo,
> 
> Lorenzo Pieralisi <lorenzo.pieralisi@....com> wrote on Wed, 23 Jan 2019
> 17:05:09 +0000:
> 
> > On Tue, Jan 08, 2019 at 05:24:25PM +0100, Miquel Raynal wrote:
> > > Hello,
> > > 
> > > As part of an effort to bring suspend to RAM support to Armada 3700
> > > SoCs (main target: ESPRESSObin), this series handles the work around
> > > the PCIe IP.
> > > 
> > > First, more configuration is done in the 'setup' helper as inspired
> > > from the U-Boot driver. This is needed to entirely initialize the IP
> > > during future resume operation (patch 1).
> > > 
> > > Then, reset GPIO, PHY and clock support are introduced (patch 2-4). As
> > > current device trees do not provide the corresponding properties, not
> > > finding one of these properties is not an error and just produces a
> > > warning. However, if the property is present, an error during PHY
> > > initialization will fail the probe of the driver.
> > > 
> > > Note: To be sure the clock will be resumed before this driver, a first
> > > series adding links between clocks and consumers has been submitted,
> > > see [1]. Anyway, having the clock series applied first is not needed.  
> > 
> > I do not understand what this means, in particular in relation
> > to the blocking clock calls in the suspend/resume NOIRQ hooks.
> 
> I am not sure to understand your question.
> 
> As there are multiple points in this sentence I will detail each of
> them so please comment on the one which is bothering you:
> * I am working in parallel on a series adding device links to the clock
>   framework. This way when a driver consumes a clock, the clock
>   provider driver will be resumed first.
> * If the clock series I am talking about is applied after this one,
>   there is no build issue. Of course suspending the platform may
>   not work but this is a new feature so nothing will be broken.

Suspend to RAM will be broken if the clock is suspended and no
notification will happen in the NOIRQ phase, it is a new-broken-feature.

> * Device links do not enforce any priority if the suspend/resume phase
>   between two drivers is not the same. The PCIe driver suspends in the
>   NOIRQ phase. If we want the clock driver to suspend *after* PCIe, its
>   suspend/resume callbacks must be promoted to the NOIRQ phase as well
>   (and this is part of another series). As of today there is
>   no alternative.

I will merge this series when it works, I have no evidence that it does
given what you are writing above, if the series you mention are
*necessary* for suspend-to-RAM to work they ought to be merged first.

Thanks,
Lorenzo