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

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Date:   Mon, 3 Dec 2018 23:18:44 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        sudeep.holla@....com,
        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 05/12] PCI: aardvark: add suspend to RAM support

Hi Rafael, Stephen,

"Rafael J. Wysocki" <rjw@...ysocki.net> wrote on Mon, 03 Dec 2018
23:00:20 +0100:

> On Monday, December 3, 2018 4:38:46 PM CET Miquel Raynal wrote:
> > Hi Lorenzo,
> > 
> > Lorenzo Pieralisi <lorenzo.pieralisi@....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@...tlin.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
> 

Thank you both for the enlightenment.


Thanks,
Miquèl