On Mon, Aug 29, 2022 at 07:23:32PM +0100, Maciej W. Rozycki wrote: > The Intel 82378ZB System I/O (SIO) and 82379AB System I/O APIC (SIO.A) > ISA bridges implement PCI interrupt steering with a PIRQ router[1][2] > that is exactly the same as that of the PIIX and ICH southbridges (or > actually the other way round, given that the SIO ASIC was there first). > > An earlier version of the SIO, the 82378IB[3][4], does not implement PCI > interrupt steering however, so we need to exclude it by checking the low > nibble of the PCI Revision Identification Register[5][6] for being at > least 3. > > There is a note in the 82379AB specification update[7] saying that the > device ID for that chip is 0x7, rather than 0x484 as stated in the > datasheet[8]. It looks like a red herring however, for no report has > been ever seen with that value quoted and it matches the documented > default value of the PCI Command Register, which comes next after the > PCI Device Identification Register, so it looks like a copy-&-paste > editorial mistake. > > NB the 82378ZB has been commonly used with smaller DEC Alpha systems > with the contents of the Revision Identification Register reported as > one of 0x3, 0x43, or 0x84, so the masking of the high nibble seems > indeed right by empirical observation. The value in the high nibble > might be either random, or depend on the batch, or correspond to some > other state such as reset straps. > > References: > > [1] "82378 System I/O (SIO)", Intel Corporation, Order Number: > 290473-004, December 1994, Section 4.1.26 "PIRQ[3:0]#--PIRQ Route > Control Registers" > > [2] "82378ZB System I/O (SIO) and 82379AB System I/O APIC (SIO.A)", > Intel Corporation, Order Number: 290571-001, March 1996, Section > 3.1.25. "PIRQ[3:0]#--PIRQ Route Control Registers", p. 48 > > [3] "82378IB System I/O (SIO)", Intel Corporation, Order Number: > 290473-002, April 1993, Section 5.8.7.7 "Edge and Level Triggered > Modes" > > [4] "82378IB to 82378ZB Errata Fix and Feature Enhancement Conversion > FOL933002-01", > <https://web.archive.org/web/19990421045433/http://support.intel.com/support/chipsets/420/8511.htm> > > [5] "82378 System I/O (SIO)", Intel Corporation, Order Number: > 290473-004, December 1994, Section 4.1.5. "RID--Revision > Identification Register" > > [6] "82378ZB System I/O (SIO) and 82379AB System I/O APIC (SIO.A)", > Intel Corporation, Order Number: 290571-001, March 1996, Section > 3.1.5. "RID--Revision Identification Register", p. 34 > > [7] "Intel 82379AB (SIO.A) System I/O Component Specification Update", > Intel Corporation, Order Number: 297734-001, May, 1996, "Component > Identification via Programming Interface", p. 5 > > [8] "82378ZB System I/O (SIO) and 82379AB System I/O APIC (SIO.A)", > Intel Corporation, Order Number: 290571-001, March 1996, Section > 3.1.2. "DID--Device Identification Register", p. 33 > > Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx> > --- > Hi, > > This patch was dropped from x86/irq due to a bug in a follow-up patch and > when resent it was not re-picked up along with the other patches for some > reason, so resending verbatim again after another re-verification, against > 6.0-rc2 as at yesterday (just before Linus's version bump). I don't know anything about these IRQ routers, and Thomas has applied recent similar patches, so I assume he'll handle this.
