From 0962289b1cd91534f7111e763d3e6a17dcd47ecb Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Fri, 27 Oct 2017 10:34:22 +0200 Subject: irqchip/gic: Deal with broken firmware exposing only 4kB of GICv2 CPU interface 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: Christoffer Dall Signed-off-by: Marc Zyngier --- Documentation/admin-guide/kernel-parameters.txt | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 05496622b4ef..3daa0a590236 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1713,6 +1713,13 @@ irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. + irqchip.gicv2_force_probe= + [ARM, ARM64] + Format: + Force the kernel to look for the second 4kB page + of a GICv2 controller even if the memory range + exposed by the device tree is too small. + irqfixup [HW] When an interrupt is not handled search all handlers for it. Intended to get systems with badly broken -- cgit v1.2.1