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

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Message-ID: <20160218150852.GA17588@localhost>
Date:	Thu, 18 Feb 2016 09:08:52 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	"Sharma, Sanjeev" <Sanjeev_Sharma@...tor.com>
Cc:	"Richard.Zhu@...escale.com" <Richard.Zhu@...escale.com>,
	"l.stach@...gutronix.de" <l.stach@...gutronix.de>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Mueller <dave.mueller@....ch>
Subject: Re: [PATCH] PCI: imx6:don't sleep in atomic context

On Thu, Feb 18, 2016 at 07:17:41AM +0000, Sharma, Sanjeev wrote:
> -----Original Message-----
> From: Bjorn Helgaas [mailto:helgaas@...nel.org] 
> Sent: Thursday, January 07, 2016 3:35 AM
> To: Sharma, Sanjeev
> Cc: Richard.Zhu@...escale.com; l.stach@...gutronix.de; bhelgaas@...gle.com; linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; David Mueller
> Subject: Re: [PATCH] PCI: imx6:don't sleep in atomic context
> 
> Hi Sanjeev,
> 
> On Mon, Nov 09, 2015 at 04:18:00PM +0530, Sanjeev Sharma wrote:
> > If additional PCIe switch get connected between the host and the 
> > NIC,the kernel crashes with "BUG:
> > scheduling while atomic". To handle this we need to call mdelay() 
> > instead of usleep_range().
> > 
> > For more detail please refer bugzilla.kernel.org, Bug
> > 100031
> > 
> > Signed-off-by: Sanjeev Sharma <sanjeev_sharma@...tor.com>
> > Signed-off-by: David Mueller <dave.mueller@....ch>
> 
> I'm dropping this for now because we've been kicking around the same solution (with tweaks to the mdelay amount) since June, but no progress on the *real* issue, which is that imx6_pcie_link_up() should never wait; it should simply return the link status.
> 
> I'm pretty sure the amount of time I've spent looking into this would have been enough to make some progress on that underlying issue.
> 
> Bjorn
> 
> Ok ! please share the change you are planning to implement. 

I didn't mean I personally was going to do this.  But I think Lucas
stepped up and did it:

https://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/commit/?h=pci/host-imx6&id=4d107d3b5a686b5834e533a00b73bf7b1cf59df7

> > ---
> >  drivers/pci/host/pci-imx6.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > 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);
> >  	}
> >  	/*
> >  	 * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
> > --
> > 1.7.11.7
> > 
> > --
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