[linuxppc-release][PATCH] powerpc/pci-hotplug: fix init issue of rescanned pci device
Bjorn Helgaas
bhelgaas at google.com
Sat Dec 8 08:15:46 EST 2012
On Thu, Dec 6, 2012 at 4:23 AM, Chen Yuanquan-B41889
<B41889 at freescale.com> wrote:
> On 12/06/2012 05:30 AM, Bjorn Helgaas wrote:
>>
>> On Wed, Dec 5, 2012 at 2:29 AM, Chen Yuanquan-B41889
>> <B41889 at freescale.com> wrote:
>>>
>>> On 12/05/2012 04:26 PM, Benjamin Herrenschmidt wrote:
>>>>
>>>> On Wed, 2012-12-05 at 16:20 +0800, Chen Yuanquan-B41889 wrote:
>>>>>
>>>>> 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.
>>>>
>>>> Please, at least format your email properly so I can try to undertand
>>>> without needing aspirin.
>>>>
>>>>> 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.
>>>>
>>>> First, none of that invalidates my statement that you shouldn't
>>>> duplicate a whole block of code like this. Even if your approach is
>>>> correct (which is debated separately), at the very least you should
>>>> factor the code out into a common function between the two copies.
>>>>
>>>>> 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.
>>>>
>>>> Where ? How ? What is the sequence happening ? In any case, I think if
>>>> we need a proper fixup done per-device like that after scan we ought to
>>>> create a new hook at the generic level rather than that sort of hack.
>>>>
>>> echo 1 > rescan to trigger dev_rescan_store:
>>>
>>> dev_rescan_store->pci_rescan_bus->pci_scan_child_bus,
>>> pci_assign_unassigned_bus_resources,
>>> pci_enable_bridges, pci_bus_add_devices
>>>
>>>
>>> pci_enable_bridges->pci_enable_device->__pci_enable_device_flags->do_pci_enable_device->
>>> pcibios_enable_device
>>>
>>> pci_bus_add_devices->pci_bus_add_device->"dev->is_added = 1"
>>>
>>> Yeah, it's general fixup code for every rescanned PCI/PCI-e device on
>>> powerpc at runtime. So if
>>> we want to call it in a ppc_md member, we need to wrap it as a function
>>> and
>>> assign it in every ppc_md,
>>> it isn't proper for the general code.
>>>
>>> Regards,
>>> yuanquan
>>>
>>>
>>>>> 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.
>>>>
>>>> Who calls pci_enable_device() in the rescan case ? Why isn't it left to
>>>> the driver ? I don't think we can rely on that behaviour not to change.
>>>>
>>>>>> 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.
>>>>
>>>> Yeah this code path are known to be fishy. I think the problem is at the
>>>> generic abstraction level and that's where it needs to be fixed.
>>>>
>>>> Cheers,
>>>> Ben.
>>>>
>>>>> 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 <B41889 at freescale.com>
>>>>>>> ---
>>>>>>> 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);
>>>>>>> }
>>
>> Is this the same issue Hiroo MATSUMOTO was working on earlier?
>> (http://comments.gmane.org/gmane.linux.ports.ppc.embedded/50080)
>
>
> Yeah, that's the exact problem I encountered. Please push it forward.
Well, as I mentioned, there are unresolved issues, so it's not just a
matter of applying the most recent patch. If you're interested in
this problem and have some hardware to test, you can help by looking
into some of the things I mentioned in the message at the URL below.
>> We went round and round on those patches (partly my fault for
>> excessive bike-shedding), and then we stalled out because of an
>> ordering issue with CardBus init and an IRQ quirk.
>>
>> Here's the last status I remember:
>> http://marc.info/?l=linux-pci&m=135006501620378&w=2
>>
>> Bjorn
>>
>>
>>
>
>
More information about the Linuxppc-dev
mailing list