Armada XP (mvebu) Hot-plug issues continued

Hi Guys,

This is something of a follow up to my previous thread:
Armada XP (mvebu) PCIe memory (BAR/window) re-allocation

Thanks to the helpful patches provided to the mvebu PCIe subsystem, hot-plug PCIe devices worked much better on this board, however I have discovered one remaining issue regarding them, due to the fact the legacy style IRQ is assigned during the fake "PCI BIOS" phase, devices which are plugged after boot will not be given an IRQ and thus if they do not support MSI/MSI-X will fail to initialize.

This seems a fairly simple problem to squash and as such I have written a small patch which helps solve this, however I am unsure if I am doing this in a sensible way or if a different kind of rework is needed here. Also, if this is the wrong mailing list to ask about this please say so.

Any comments regarding this patch or a better way to achieve this would be greatly appreciated. Patch follows (sorry if the format is off, still getting used to git format-patch).

Many thanks,
Matthew

From: matthew_minter <[email protected]>
Date: Wed, 9 Jul 2014 17:51:07 +0100
Subject: [PATCH RFC] Added code to ensure hot-added PCI devices are given an
IRQ on rescan
To: linux-arm-kernel at lists.infradead.org

---
 drivers/pci/bus.c       | 11 +++++++++++
 drivers/pci/setup-irq.c |  2 +-
 include/linux/pci.h     |  2 ++
 3 files changed, 14 insertions(+), 1 deletion(-)

index 73aef51..eb4f93c 100644
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
+#include <linux/of_pci.h>
 #include <linux/errno.h>
 #include <linux/ioport.h>
 #include <linux/proc_fs.h>

@@ -245,6 +246,16 @@ void pci_bus_add_device(struct pci_dev *dev)
      * are not assigned yet for some devices.
      */
     pci_fixup_device(pci_fixup_final, dev);
+    /*
+     * Devices which are hot-added after boot have not
+     * been assigned an irq by the bios.
+     */
+    if (unlikely(!dev->irq)) {
+        dev_dbg(&dev->dev,
+            "PCI device missing IRQ, attempting to assign one\n");
+        pdev_fixup_irq(dev, pci_common_swizzle,
+            of_irq_parse_and_map_pci);
+    }
     pci_create_sysfs_dev_files(dev);
     pci_proc_attach_device(dev);
 

index 4e2d595..38c96c8 100644
@@ -22,7 +22,7 @@ void __weak pcibios_update_irq(struct pci_dev *dev, int irq)
     pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
 }
 
-static void pdev_fixup_irq(struct pci_dev *dev,
+void pdev_fixup_irq(struct pci_dev *dev,
                u8 (*swizzle)(struct pci_dev *, u8 *),
                int (*map_irq)(const struct pci_dev *, u8, u8))
 {

index 466bcd1..4c1b1b3 100644
@@ -1056,6 +1056,8 @@ void pci_assign_unassigned_bus_resources(struct

pci_bus *bus);
void pci_assign_unassigned_root_bus_resources(struct pci_bus *bus); void pdev_enable_device(struct pci_dev *);
int pci_enable_resources(struct pci_dev *, int mask);
+void pdev_fixup_irq(struct pci_dev *, u8 (*)(struct pci_dev *, u8 *),
+ int (*)(const struct pci_dev *, u8, u8));
void pci_fixup_irqs(u8 (*)(struct pci_dev *, u8 *),

             int (*)(const struct pci_dev *, u8, u8));

#define HAVE_PCI_REQ_REGIONS 2

2.0.0

-- 


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Dear Matthew Minter,

My knowledge of the PCI core is a bit too limited to judge whether this is the right solution or not.

However, I would recommend you to send the patch and problem description to the linux-pci at vger.kernel.org mailing list, with Bjorn Helgaas <[email protected]> in the recipients (he is the PCI subsystem maintainer).

It would indeed be good if you could use git send-email, because your patch has been badly modified by your e-mail client :/

Best regards,

Thomas

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com