On Thu, Dec 6, 2012 at 4:23 AM, Chen Yuanquan-B41889
[off-list ref] wrote:

On 12/06/2012 05:30 AM, Bjorn Helgaas wrote:

quoted

On Wed, Dec 5, 2012 at 2:29 AM, Chen Yuanquan-B41889
[off-list ref] wrote:

quoted

On 12/05/2012 04:26 PM, Benjamin Herrenschmidt wrote:

quoted

On Wed, 2012-12-05 at 16:20 +0800, Chen Yuanquan-B41889 wrote:

quoted

On 12/05/2012 03:17 PM, Benjamin Herrenschmidt wrote:

quoted

On Wed, 2012-12-05 at 10:31 +0800, Yuanquan Chen wrote:

quoted

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.

quoted

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.

quoted

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.

quoted

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

quoted

quoted

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.

quoted

quoted

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.

quoted

Regards,
yuanquan

quoted

I think the problem needs to be solve at a higher level, I'm adding
linux-pci & Bjorn to the CC list.

Cheers,
Ben.

quoted

Signed-off-by: Yuanquan Chen <redacted>
---
    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.

quoted

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