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

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Date:   Fri, 25 Jan 2019 11:05:30 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....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

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.
* 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.


Thanks,
Miquèl