Subject: Re: [linuxppc-release][PATCH] powerpc/pci-hotplug: fix init issue of rescanned pci device

From: Chen Yuanquan-B41889 <[email-masked]>
Date: Wed, 5 Dec 2012 16:20:17 +0800

On 12/05/2012 03:17 PM, Benjamin Herrenschmidt wrote:
> On Wed, 2012-12-05 at 10:31 +0800, Yuanquan Chen wrote:
>> On powerpc arch, some fixup work of PCI/PCI-e device is just done during the
>> first scan at booting time. For the PCI/PCI-e device rescanned after linux OS
>> booting up, the fixup work won't be done, which leads to dma_set_mask error or
>> irq related issue in rescanned PCI/PCI-e device's driver. So, it does the same
>> fixup work for the rescanned device to avoid this issue.
> Hrm, the patch is a bit gross. First the code shouldn't be copy/pasted
> that way but factored out.
There's a judgement "if (!bus->is_added)" before calling of 
pcibios_fixup_bus
in pci_scan_child_bus, so for the rescanned device, the fixup won't execute,
which leads to fatal error in driver of rescanned device on freescale 
powerpc, no
this issues on x86 arch. Remove the judgement, let it to do the 
pcibios_fixup_bus
directly, the error won't occur for the rescanned device. But it's 
general code, not
proper to change here, so copy the pcibios_fixup_bus work to 
pcibios_enable_device.
> I'm surprised also that is_added is false when pcibios_enable_device()
> gets called ... that looks strange to me. At what point is that enable
> happening in the hotplug sequence ?
All devices are rescanned and then call the pci_enable_devices and 
pci_bus_add_devices.
The patch code will be called by pci_enable_devices. The "dev->is_added" 
is set in pci_bus_add_device
which is called by pci_bus_add_devices. So "dev->is_added" is false when 
checking it in pcibios_enable_device
for the rescanned device.
> How do you trigger the rescan anyway ?
Use the interface under /sys :
echo 1 > /sys/bus/pci/devices/xxx/remove

then echo 1 to the pci device which is the bus of the removed device
echo 1 > /sys/bus/pci/devices/xxxx/rescan
the removed device will be scanned and it's driver module will be loaded 
automatically.

Regards,
yuanquan
> I think the problem needs to be solve at a higher level, I'm adding
> linux-pci & Bjorn to the CC list.
>
> Cheers,
> Ben.
>
>> Signed-off-by: Yuanquan Chen <[email-masked]>
>> ---
>>   arch/powerpc/kernel/pci-common.c |   20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
>> index 7f94f76..f0fb070 100644
>> --- a/arch/powerpc/kernel/pci-common.c
>> +++ b/arch/powerpc/kernel/pci-common.c
>> @@ -1496,6 +1496,26 @@ int pcibios_enable_device(struct pci_dev *dev, int mask)
>>   		if (ppc_md.pcibios_enable_device_hook(dev))
>>   			return -EINVAL;
>>   
>> +	if (!dev->is_added) {
>> +		/*
>> +		 * Fixup NUMA node as it may not be setup yet by the generic
>> +		 * code and is needed by the DMA init
>> +		 */
>> +		set_dev_node(&dev->dev, pcibus_to_node(dev->bus));
>> +
>> +		/* Hook up default DMA ops */
>> +		set_dma_ops(&dev->dev, pci_dma_ops);
>> +		set_dma_offset(&dev->dev, PCI_DRAM_OFFSET);
>> +
>> +		/* Additional platform DMA/iommu setup */
>> +		if (ppc_md.pci_dma_dev_setup)
>> +			ppc_md.pci_dma_dev_setup(dev);
>> +
>> +		/* Read default IRQs and fixup if necessary */
>> +		pci_read_irq_line(dev);
>> +		if (ppc_md.pci_irq_fixup)
>> +			ppc_md.pci_irq_fixup(dev);
>> +	}
>>   	return pci_enable_resources(dev, mask);
>>   }
>>   
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