• Maciej W. Rozycki's avatar
    x86: Add support for 0x22/0x23 port I/O configuration space · fb6a0408
    Maciej W. Rozycki authored
    Define macros and accessors for the configuration space addressed 
    indirectly with an index register and a data register at the port I/O 
    locations of 0x22 and 0x23 respectively.
    
    This space is defined by the Intel MultiProcessor Specification for the 
    IMCR register used to switch between the PIC and the APIC mode[1], by 
    Cyrix processors for their configuration[2][3], and also some chipsets.
    
    Given the lack of atomicity with the indirect addressing a spinlock is 
    required to protect accesses, although for Cyrix processors it is enough 
    if accesses are executed with interrupts locally disabled, because the 
    registers are local to the accessing CPU, and IMCR is only ever poked at 
    by the BSP and early enough for interrupts not to have been configured 
    yet.  Therefore existing code does not have to change or use the new 
    spinlock and neither it does.
    
    Put the spinlock in a library file then, so that it does not get pulled 
    unnecessarily for configurations that do not refer it.
    
    Convert Cyrix accessors to wrappers so as to retain the brevity and 
    clarity of the `getCx86' and `setCx86' calls.
    
    References:
    
    [1] "MultiProcessor Specification", Version 1.4, Intel Corporation, 
        Order Number: 242016-006, May 1997, Section 3.6.2.1 "PIC Mode", pp. 
        3-7, 3-8
    
    [2] "5x86 Microprocessor", Cyrix Corporation, Order Number: 94192-00, 
        July 1995, Section 2.3.2.4 "Configuration Registers", p. 2-23
    
    [3] "6x86 Processor", Cyrix Corporation, Order Number: 94175-01, March 
        1996, Section 2.4.4 "6x86 Configuration Registers", p. 2-23
    Signed-off-by: default avatarMaciej W. Rozycki <macro@orcam.me.uk>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Link: https://lore.kernel.org/r/alpine.DEB.2.21.2107182353140.9461@angie.orcam.me.uk
    fb6a0408
apic.c 73.8 KB