linux-kernel - Re: [PATCH] PCI: imx6:don't sleep in atomic context

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Date:	Tue, 10 Nov 2015 10:35:10 +0100
From:	Lucas Stach <l.stach@...gutronix.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Sanjeev Sharma <sanjeev_sharma@...tor.com>,
	linux-pci@...r.kernel.org, Richard.Zhu@...escale.com,
	linux-kernel@...r.kernel.org, David Mueller <dave.mueller@....ch>,
	bhelgaas@...gle.com
Subject: Re: [PATCH] PCI: imx6:don't sleep in atomic context

Am Dienstag, den 10.11.2015, 10:28 +0100 schrieb Arnd Bergmann:
> On Tuesday 10 November 2015 09:41:18 Lucas Stach wrote:
> > > diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> > > index 233a196..9769b13 100644
> > > --- a/drivers/pci/host/pci-imx6.c
> > > +++ b/drivers/pci/host/pci-imx6.c
> > > @@ -499,7 +499,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> > >                * Wait a little bit, then re-check if the link finished
> > >                * the training.
> > >                */
> > > -             usleep_range(1000, 2000);
> > > +             mdelay(1000);
> > 
> > A mdelay(1000) is a whole different timescale than a usleep(1000). If
> > this patch works for you with mdelay(1) or maybe mdelay(2) I would be
> > fine with it.
> 
> mdelay(1) is still a really long time to block the CPU for, on potentially
> every config space access.
> 
> Everybody else just returns the link status here, which seems to be
> the better alternative. If you need to delay the startup, better have
> a msleep(1) loop in the initial probe function where you are allowed to
> sleep.
> 
Yes, it's somewhere on my TODO list to rework the link-up handling here,
but as there are quite a few timing and ordering implications in that
code, this needs a good thought and a good deal of testing. So I'm
inclined to ACK the current patch to get rid of the obvious bug and sort
things out properly in a follow on patchset.

Regards,
Lucas

-- 
Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |

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