@@ -28,6 +28,32 @@
* this allows a newer kernel to use the INTERRUPT_LINE
* registers arbitrarily once it has indicated that it isn't
* broken in its init code somewhere.
+ *
+ * Unfortunately we have to cope with multiple different
+ * variants on the broken kernel behaviour:
+ * phase I (before kernel commit 1bc39ac5d) kernels assume old
+ * QEMU behaviour, so they use IRQ 27 for all slots
+ * phase II (1bc39ac5d and later, but before e3e92a7be6) kernels
+ * swizzle IRQs between slots, but do it wrongly, so they
+ * work only for every fourth PCI card, and only if (like old
+ * QEMU) the PCI host device is at slot 0 rather than where
+ * the h/w actually puts it
+ * phase III (e3e92a7be6 and later) kernels still swizzle IRQs between
+ * slots wrongly, but add a fixed offset of 64 to everything
+ * they write to PCI_INTERRUPT_LINE.
+ *
+ * We live in hope of a mythical phase IV kernel which might
+ * actually behave in ways that work on the hardware. Such a
+ * kernel should probably start off by writing some value neither
+ * 27 nor 91 to slot zero's PCI_INTERRUPT_LINE register to
+ * disable the autodetection. After that it can do what it likes.
+ *
+ * Slot % 4 | hw | I | II | III
+ * -------------------------------
+ * 0 | 29 | 27 | 27 | 91
+ * 1 | 30 | 27 | 28 | 92
+ * 2 | 27 | 27 | 29 | 93
+ * 3 | 28 | 27 | 30 | 94
*/
enum {
PCI_VPB_IRQMAP_ASSUME_OK,
@@ -214,6 +240,41 @@ static const MemoryRegionOps pci_vpb_reg_ops = {
},
};
+static int pci_vpb_broken_irq(int slot, int irq)
+{
+ /* Determine whether this IRQ value for this slot represents a
+ * known broken Linux kernel behaviour for this slot.
+ * Return one of the PCI_VPB_IRQMAP_ constants:
+ * BROKEN : if this definitely looks like a broken kernel
+ * FORCE_OK : if this definitely looks good
+ * ASSUME_OK : if we can't tell
+ */
+ slot %= PCI_NUM_PINS;
+
+ if (irq == 27) {
+ if (slot == 2) {
+ /* Might be a Phase I kernel, or might be a fixed kernel,
+ * since slot 2 is where we expect this IRQ.
+ */
+ return PCI_VPB_IRQMAP_ASSUME_OK;
+ }
+ /* Phase I kernel */
+ return PCI_VPB_IRQMAP_BROKEN;
+ }
+ if (irq == slot + 27) {
+ /* Phase II kernel */
+ return PCI_VPB_IRQMAP_BROKEN;
+ }
+ if (irq == slot + 27 + 64) {
+ /* Phase III kernel */
+ return PCI_VPB_IRQMAP_BROKEN;
+ }
+ /* Anything else must be a fixed kernel, possibly using an
+ * arbitrary irq map.
+ */
+ return PCI_VPB_IRQMAP_FORCE_OK;
+}
+
static void pci_vpb_config_write(void *opaque, hwaddr addr,
uint64_t val, unsigned size)
{
@@ -221,13 +282,7 @@ static void pci_vpb_config_write(void *opaque, hwaddr addr,
if (!s->realview && (addr & 0xff) == PCI_INTERRUPT_LINE
&& s->irq_mapping == PCI_VPB_IRQMAP_ASSUME_OK) {
uint8_t devfn = addr >> 8;
- if ((PCI_SLOT(devfn) % PCI_NUM_PINS) != 2) {
- if (val == 27) {
- s->irq_mapping = PCI_VPB_IRQMAP_BROKEN;
- } else {
- s->irq_mapping = PCI_VPB_IRQMAP_FORCE_OK;
- }
- }
+ s->irq_mapping = pci_vpb_broken_irq(PCI_SLOT(devfn), val);
}
pci_data_write(&s->pci_bus, addr, val, size);
}
Newer versatilepb kernels still don't get the IRQ mapping right for the PCI controller, but they get it differently wrong (they add a fixed +64 offset to everything they write to PCI_INTERRUPT_LINE). Update the autodetection to handle these too, and include a more detailed comment on the various different behaviours that might be present. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- hw/pci-host/versatile.c | 69 ++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 62 insertions(+), 7 deletions(-)