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hw/pci-host/versatile.c: Update autodetect to detect newer kernels 

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>
Message-id: 1368545616-22344-3-git-send-email-peter.maydell@linaro.org
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Peter Maydell 2013-05-14 16:33:35 +01:00 committed by Anthony Liguori
parent 33201b51cb
commit bc04d89165
1 changed files with 62 additions and 7 deletions
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69
hw/pci-host/versatile.c
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@ -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);
}