• Marc Zyngier's avatar
    irqchip/gic: Deal with broken firmware exposing only 4kB of GICv2 CPU interface · 0962289b
    Marc Zyngier authored
    There is a lot of broken firmware out there that don't really
    expose the information the kernel requires when it comes with dealing
    with GICv2:
    (1) Firmware that only describes the first 4kB of GICv2
    (2) Firmware that describe 128kB of CPU interface, while
        the usable portion of the address space is between
        60 and 68kB
    So far, we only deal with (2). But we have platforms exhibiting
    behaviour (1), resulting in two sub-cases:
    (a) The GIC is occupying 8kB, as required by the GICv2 architecture
    (b) It is actually spread 128kB, and this is likely to be a version
        of (2)
    This patch tries to work around both (a) and (b) by poking at
    the outside of the described memory region, and try to work out
    what is actually there. This is of course unsafe, and should
    only be enabled if there is no way to otherwise fix the DT provided
    by the firmware (we provide a "irqchip.gicv2_force_probe" option
    to that effect).
    Note that for the time being, we restrict ourselves to GICv2
    implementations provided by ARM, since there I have no knowledge
    of an alternative implementations. This could be relaxed if such
    an implementation comes to light on a broken platform.
    Reviewed-by: default avatarChristoffer Dall <cdall@linaro.org>
    Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
kernel-parameters.txt 160 KB