Handle the $IRT PCI IRQ Routing Table format used by AMI for its BCP (BIOS Configuration Program) external tool meant for tweaking BIOS structures without the need to rebuild it from sources[1]. The $IRT format has been invented by AMI before Microsoft has come up with its $PIR format and a $IRT table is therefore there in some systems that lack a $PIR table, such as the DataExpert EXP8449 mainboard based on the ALi FinALi 486 chipset (M1489/M1487), which predates DMI 2.0 and cannot therefore be easily identified at run time. Unlike with the $PIR format there is no alignment guarantee as to the placement of the $IRT table, so scan the whole BIOS area bytewise. Credit to Michal Necasek for helping me chase documentation for the format. References: [1] "What is BCP? - AMI", <https://www.ami.com/what-is-bcp/> Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx> Cc: Michal Necasek <mnecasek@xxxxxxxxx> --- New change in v3. --- arch/x86/include/asm/pci_x86.h | 9 +++++ arch/x86/pci/irq.c | 71 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 80 insertions(+) linux-x86-pirq-irt.diff Index: linux-macro/arch/x86/include/asm/pci_x86.h =================================================================== --- linux-macro.orig/arch/x86/include/asm/pci_x86.h +++ linux-macro/arch/x86/include/asm/pci_x86.h @@ -90,6 +90,15 @@ struct irq_routing_table { struct irq_info slots[0]; } __attribute__((packed)); +struct irt_routing_table { + u32 signature; /* IRT_SIGNATURE should be here */ + u8 size; /* Number of entries provided */ + u8 used; /* Number of entries actually used */ + u16 exclusive_irqs; /* IRQs devoted exclusively to + PCI usage */ + struct irq_info slots[0]; +} __attribute__((packed)); + extern unsigned int pcibios_irq_mask; extern raw_spinlock_t pci_config_lock; Index: linux-macro/arch/x86/pci/irq.c =================================================================== --- linux-macro.orig/arch/x86/pci/irq.c +++ linux-macro/arch/x86/pci/irq.c @@ -25,6 +25,8 @@ #define PIRQ_SIGNATURE (('$' << 0) + ('P' << 8) + ('I' << 16) + ('R' << 24)) #define PIRQ_VERSION 0x0100 +#define IRT_SIGNATURE (('$' << 0) + ('I' << 8) + ('R' << 16) + ('T' << 24)) + static int broken_hp_bios_irq9; static int acer_tm360_irqrouting; @@ -91,7 +93,69 @@ static inline struct irq_routing_table * return NULL; } +/* + * Handle the $IRT PCI IRQ Routing Table format used by AMI for its BCP + * (BIOS Configuration Program) external tool meant for tweaking BIOS + * structures without the need to rebuild it from sources. The $IRT + * format has been invented by AMI before Microsoft has come up with its + * $PIR format and a $IRT table is therefore there in some systems that + * lack a $PIR table. + * + * It uses the same PCI BIOS 2.1 format for interrupt routing entries + * themselves but has a different simpler header prepended instead, + * occupying 8 bytes, where a `$IRT' signature is followed by one byte + * specifying the total number of interrupt routing entries allocated in + * the table, then one byte specifying the actual number of entries used + * (which the BCP tool can take advantage of when modifying the table), + * and finally a 16-bit word giving the IRQs devoted exclusively to PCI. + * Unlike with the $PIR table there is no alignment guarantee. + * + * Given the similarity of the two formats the $IRT one is trivial to + * convert to the $PIR one, which we do here, except that obviously we + * have no information as to the router device to use, but we can handle + * it by matching PCI device IDs actually seen on the bus against ones + * that our individual routers recognise. + * + * Reportedly there is another $IRT table format where a 16-bit word + * follows the header instead that points to interrupt routing entries + * in a $PIR table provided elsewhere. In that case this code will not + * be reached though as the $PIR table will have been chosen instead. + */ +static inline struct irq_routing_table *pirq_convert_irt_table(u8 *addr) +{ + struct irt_routing_table *ir; + struct irq_routing_table *rt; + u16 size; + u8 sum; + int i; + + ir = (struct irt_routing_table *)addr; + if (ir->signature != IRT_SIGNATURE || !ir->used || ir->size < ir->used) + return NULL; + DBG(KERN_DEBUG "PCI: $IRT Interrupt Routing Table found at 0x%lx\n", + __pa(ir)); + + size = sizeof(*rt) + ir->used * sizeof(rt->slots[0]); + rt = kzalloc(size, GFP_KERNEL); + if (!rt) + return NULL; + + rt->signature = PIRQ_SIGNATURE; + rt->version = PIRQ_VERSION; + rt->size = size; + rt->exclusive_irqs = ir->exclusive_irqs; + for (i = 0; i < ir->used; i++) + rt->slots[i] = ir->slots[i]; + + addr = (u8 *)rt; + sum = 0; + for (i = 0; i < size; i++) + sum += addr[i]; + rt->checksum = -sum; + + return rt; +} /* * Search 0xf0000 -- 0xfffff for the PCI IRQ Routing Table. @@ -113,6 +177,13 @@ static struct irq_routing_table * __init if (rt) return rt; } + for (addr = (u8 *)__va(0xf0000); + addr < (u8 *)__va(0x100000); + addr++) { + rt = pirq_convert_irt_table(addr); + if (rt) + return rt; + } return NULL; }
