Commit b584db0c authored by Maciej W. Rozycki's avatar Maciej W. Rozycki Committed by Thomas Gleixner
Browse files

x86/PCI: Add $IRT PIRQ routing table support 

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: default avatarMaciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> # crosvm
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2203302228410.9038@angie.orcam.me.uk
parent ac7cd5e1

arch/x86/include/asm/pci_x86.h

+9 −0
Original line number Diff line number Diff line
@@ -93,6 +93,15 @@ struct irq_routing_table { 
	struct irq_info slots[];

} __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[];

} __attribute__((packed));



extern unsigned int pcibios_irq_mask;



extern raw_spinlock_t pci_config_lock;

arch/x86/pci/irq.c

+76 −0
Original line number Diff line number Diff line
@@ -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;
@@ -93,7 +95,74 @@ static inline struct irq_routing_table *pirq_check_routing_table(u8 *addr, 
	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,

							       u8 *limit)

{

	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;



	size = sizeof(*ir) + ir->used * sizeof(ir->slots[0]);

	if (size > limit - addr)

		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.
@@ -120,6 +189,13 @@ static struct irq_routing_table * __init pirq_find_routing_table(void) 
		if (rt)

			return rt;

	}

	for (addr = bios_start;

	     addr < bios_end - sizeof(struct irt_routing_table);

	     addr++) {

		rt = pirq_convert_irt_table(addr, bios_end);

		if (rt)

			return rt;

	}

	return NULL;

}