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

From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Mark Rutland <mark.rutland@arm.com>, Andrew Lunn <andrew@lunn.ch>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	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>,
	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>,
	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 23:00:20 +0100	[thread overview]
Message-ID: <1999610.6DN9RK2Tt3@aspire.rjw.lan> (raw)
In-Reply-To: <20181203163846.494904f9@xps13>

On Monday, December 3, 2018 4:38:46 PM CET 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?
> 

Yes, it is valid.  _noirq means that the high-level action handlers will not be
invoked for interrupts occurring during that period, but that doesn't apply to
timer interrupts.

IOW, don't expect *your* IRQ handler to be invoked then (if this is not a timer
IRQ), but you can sleep.

Thanks,
Rafael

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