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

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Date:   Mon, 3 Dec 2018 17:18:59 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>, 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>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH 05/12] PCI: aardvark: add suspend to RAM support

[+Stephen, Mike]

On Mon, Dec 03, 2018 at 04:38:46PM +0100, 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?

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.

Lorenzo