Re: [PATCH 05/12] PCI: aardvark: add suspend to RAM support

From: Stephen Boyd <sboyd@kernel.org>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Mark Rutland <mark.rutland@arm.com>, Andrew Lunn <andrew@lunn.ch>,
	Jason Cooper <jason@lakedaemon.net>,
	devicetree@vger.kernel.org,
	Antoine Tenart <antoine.tenart@bootlin.com>,
	linux-pci@vger.kernel.org,
	Gregory Clement <gregory.clement@bootlin.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	linux-kernel@vger.kernel.org,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Nadav Haklai <nadavh@marvell.com>,
	Rob Herring <robh+dt@kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	sudeep.holla@arm.com, Bjorn Helgaas <bhelgaas@google.com>,
	Michael Turquette <mturquette@baylibre.com>,
	linux-arm-kernel@lists.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Subject: Re: [PATCH 05/12] PCI: aardvark: add suspend to RAM support
Date: Mon, 03 Dec 2018 11:19:22 -0800	[thread overview]
Message-ID: <154386476279.88331.4767594304261181833@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <20181203171859.GA12792@e107981-ln.cambridge.arm.com>

Quoting Lorenzo Pieralisi (2018-12-03 09:18:59)
> [+Stephen, Mike]
> 
> On Mon, Dec 03, 2018 at 04:38:46PM +0100, Miquel Raynal wrote:
> > Hi Lorenzo,
> > 
> > Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote on Mon, 3 Dec 2018
> > 10:27:08 +0000:
> > 
> > > [+Rafael, Sudeep]
> > > 
> > > On Fri, Nov 23, 2018 at 03:18:24PM +0100, Miquel Raynal wrote:
> > > > Add suspend and resume callbacks. The priority of these are
> > > > "_noirq()", to workaround early access to the registers done by the
> > > > PCI core through the ->read()/->write() callbacks at resume time.
> > > > 
> > > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > > ---
> > > >  drivers/pci/controller/pci-aardvark.c | 52 +++++++++++++++++++++++++++
> > > >  1 file changed, 52 insertions(+)
> > > > 
> > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > > > index 108b3f15c410..7ecf1ac4036b 100644
> > > > --- a/drivers/pci/controller/pci-aardvark.c
> > > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > > @@ -1108,6 +1108,55 @@ static int advk_pcie_setup_clk(struct advk_pcie *pcie)
> > > >   return ret;
> > > >  }
> > > >  
> > > > +static int __maybe_unused advk_pcie_suspend(struct device *dev)
> > > > +{
> > > > + struct advk_pcie *pcie = dev_get_drvdata(dev);
> > > > +
> > > > + advk_pcie_disable_phy(pcie);
> > > > +
> > > > + clk_disable_unprepare(pcie->clk);  
> > > 
> > > I have noticed it is common practice, still, I would like to check whether
> > > it is allowed to call functions that may sleep in a NOIRQ suspend/resume
> > > callback ?
> > 
> > You are right this is weird. I double checked and for instance,
> > pcie-mediatek.c, pci-tegra.c and pci-imx6.c do the exact same thing.
> > There are probably other cases where drivers call functions that may
> > sleep from a NOIRQ context. I am interested to know if this is valid
> > and if not, what is the alternative?
> 
> I added Stephen and Mike, who along with Rafael can help us shed some
> light into this, I do not have the necessary bits of info myself, I just
> noticed.
> 

Is the noirq phase of system suspend run with irqs disabled? Or just run
with the device irqs disabled? I thought it was the latter, which is
fine for this scenario because it's still running in a schedulable
context.

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