@@ -1417,6 +1417,38 @@ enum pci_interrupt_pin {
/* The number of legacy PCI INTx interrupts */
#define PCI_NUM_INTX 4
+/**
+ * pci_irqd_intx_xlate() - Translate PCI INTx value to an IRQ domain hwirq
+ * @d: the INTx IRQ domain
+ * @node: the DT node for the device whose interrupt we're translating
+ * @intspec: the interrupt specifier data from the DT
+ * @intsize: the number of entries in @intspec
+ * @out_hwirq: pointer at which to write the hwirq number
+ * @out_type: pointer at which to write the interrupt type
+ *
+ * Translate a PCI INTx interrupt number from device tree in the range 1-4, as
+ * stored in the standard PCI_INTERRUPT_PIN register, to a value in the range
+ * 0-3 suitable for use in a 4 entry IRQ domain. That is, subtract one from the
+ * INTx value to obtain the hwirq number.
+ *
+ * Returns 0 on success, or -EINVAL if the interrupt specifier is out of range.
+ */
+static inline int pci_irqd_intx_xlate(struct irq_domain *d,
+ struct device_node *node,
+ const u32 *intspec,
+ unsigned int intsize,
+ unsigned long *out_hwirq,
+ unsigned int *out_type)
+{
+ const u32 intx = intspec[0];
+
+ if (intx < PCI_INTERRUPT_INTA || intx > PCI_INTERRUPT_INTD)
+ return -EINVAL;
+
+ *out_hwirq = intx - PCI_INTERRUPT_INTA;
+ return 0;
+}
+
#ifdef CONFIG_PCIEPORTBUS
extern bool pcie_ports_disabled;
extern bool pcie_ports_auto;
Legacy PCI INTx interrupts are represented in the PCI_INTERRUPT_PIN register using the range 1-4, which matches our enum pci_interrupt_pin. This is however not ideal for an IRQ domain, where with 4 interrupts we would ideally have a domain of size 4 & hwirq numbers in the range 0-3. Different PCI host controller drivers have handled this in different ways. Of those under drivers/pci/ which register an INTx IRQ domain, we have: - pcie-altera uses the range 1-4 in device trees and an IRQ domain of size 5 to cover that range, with entry 0 wasted. - pcie-xilinx & pcie-xilinx-nwl use the range 1-4 in device trees but register an IRQ domain of size 4, which doesn't cover the hwirq=4/INTD case leading to that interrupt being broken. - pci-ftpci100 & pci-aardvark use the range 0-3 in both device trees & as hwirq numbering in the driver & IRQ domain. In order to introduce some level of consistency in at least the hwirq numbering used by the drivers & IRQ domains, this patch introduces a new pci_irqd_intx_xlate() helper function which drivers using the 1-4 range in device trees can assign as the xlate callback for their INTx IRQ domain. This translates the 1-4 range into a 0-3 range, allowing us to use an IRQ domain of size 4 & avoid a wasted entry. Further patches will make use of this in drivers to allow them to use an IRQ domain of size 4 for legacy INTx interrupts without breaking INTD. Signed-off-by: Paul Burton <paul.burton@imgtec.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: linux-pci@vger.kernel.org --- Changes in v7: - Rewrite the commit message. Changes in v6: - New patch. Changes in v5: None Changes in v4: None Changes in v3: None Changes in v2: None include/linux/pci.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+)