x86/PCI: Add support for the ALi M1487 (IBC) PIRQ router
The ALi M1487 ISA Bus Controller (IBC), a part of the ALi FinALi 486 chipset, implements PCI interrupt steering with a PIRQ router[1] in the form of four 4-bit mappings, spread across two PCI INTx Routing Table Mapping Registers, available in the port I/O space accessible indirectly via the index/data register pair at 0x22/0x23, located at indices 0x42 and 0x43 for the INT1/INT2 and INT3/INT4 lines respectively. Additionally there is a separate PCI INTx Sensitivity Register at index 0x44 in the same port I/O space, whose bits 3:0 select the trigger mode for INT[4:1] lines respectively[2]. Manufacturer's documentation says that this register has to be set consistently with the relevant ELCR register[3]. Add a router-specific hook then and use it to handle this register. Accesses to the port I/O space concerned here need to be unlocked by writing the value of 0xc5 to the Lock Register at index 0x03 beforehand[4]. Do so then and then lock access after use for safety. The IBC is implemented as a peer bridge on the host bus rather than a southbridge on PCI and therefore it does not itself appear in the PCI configuration space. It is complemented by the M1489 Cache-Memory PCI Controller (CMP) host-to-PCI bridge, so use that device's identification for determining the presence of the IBC. References: [1] "M1489/M1487: 486 PCI Chip Set", Version 1.2, Acer Laboratories Inc., July 1997, Section 4: "Configuration Registers", pp. 76-77 [2] same, p. 77 [3] same, Section 5: "M1489/M1487 Software Programming Guide", pp. 99-100 [4] same, Section 4: "Configuration Registers", p. 37 Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/alpine.DEB.2.21.2107191702020.9461@angie.orcam.me.uk
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