linux-kernel - Re: [Bugfix] PCI, x86: Correctly allocate IRQs for PCI devices managed by non-PCI drivers

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Date:	Thu, 10 Sep 2015 04:34:37 +0930
From:	Arthur Marsh <arthur.marsh@...ernode.on.net>
To:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
CC:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-scsi@...r.kernel.org
Subject: Re: [Bugfix] PCI, x86: Correctly allocate IRQs for PCI devices managed
 by non-PCI drivers



Jiang Liu wrote on 08/09/15 16:56:
> Commit 991de2e59090 ("PCI, x86: Implement pcibios_alloc_irq() and
> pcibios_free_irq()") changes the way to allocate PCI legacy IRQ
> for PCI devices on x86 platforms. Instead of allocating PCI legacy
> IRQs when pcibios_enable_device() gets called, now pcibios_alloc_irq()
> will be called by pci_device_probe() to allocate PCI legacy IRQs
> when binding PCI drivers to PCI devices.
>
> But some device drivers, such as eata, directly access PCI devices
> without implementing corresponding PCI drivers, so pcibios_alloc_irq()
> won't be called for those PCI devices and wrong IRQ number may be
> used to manage the PCI device.
>
> So detect such a case in pcibios_enable_device() by checking
> pci_dev->driver is NULL and call pcibios_alloc_irq() to allocate PCI
> legacy IRQs.
>
> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
> ---
>   arch/x86/pci/common.c |   10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index 09d3afc0a181..60b237783582 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -685,6 +685,16 @@ void pcibios_free_irq(struct pci_dev *dev)
>
>   int pcibios_enable_device(struct pci_dev *dev, int mask)
>   {
> +	/*
> +	 * By design, pcibios_alloc_irq() will be called by pci_device_probe()
> +	 * when binding a PCI device to a PCI driver. But some device drivers,
> +	 * such as eata, directly make use of PCI devices without implementing
> +	 * PCI device drivers, so pcibios_alloc_irq() won't be called for those
> +	 * PCI devices.
> +	 */
> +	if (!dev->driver)
> +		pcibios_alloc_irq(dev);
> +
>   	return pci_enable_resources(dev, mask);
>   }
>
>

Sorry for the late report but this patch messes up things for kexec - 
rebooting is delayed with the error messages as shown in the fuzzy 
screen image here:

http://www.users.on.net/~arthur.marsh/20150910541.jpg

(the error messages are similar to what I was seeing on boot-up before 
Jiang Liu's patch)

and the SCSI card is not recognised by the kernel after a kexec restart, 
and eata fails to load.

Arthur.
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