Messages in this thread | | | From | Duc Dang <> | Date | Fri, 22 Jan 2016 15:25:23 -0800 | Subject | Re: [PATCH 1/3] irqchip/GIC: Add workaround for aliased GIC400 |
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On Wed, Jan 20, 2016 at 1:06 AM, Marc Zyngier <marc.zyngier@arm.com> wrote: > Hi Duc, > > On Tue, 19 Jan 2016 11:12:15 -0800 > Duc Dang <dhdang@apm.com> wrote: > >> On Sun, Sep 13, 2015 at 4:14 AM, Marc Zyngier <marc.zyngier@arm.com> wrote: >> > >> > The GICv2 architecture mandates that the two 4kB GIC regions are >> > contiguous, and on two separate physical pages (so that access to >> > the second page can be trapped by a hypervisor). This doesn't work >> > very well when PAGE_SIZE is 64kB. >> > >> > A relatively common hack^Wway to work around this is to alias each >> > 4kB region over its own 64kB page. Of course in this case, the base >> > address you want to use is not really the begining of the region, >> > but base + 60kB (so that you get a contiguous 8kB region over two >> > distinct pages). >> > >> > Normally, this would be described in DT with a new property, but >> > some HW is already out there, and the firmware makes sure that >> > it will override whatever you put in the GIC node. Duh. And of course, >> > said firmware source code is not available, despite being based >> > on u-boot. >> > >> > The workaround is to detect the case where the CPU interface size >> > is set to 128kB, and verify the aliasing by checking that the ID >> > register for GIC400 (which is the only GIC wired this way so far) >> > is the same at base and base + 0xF000. In this case, we update >> > the GIC base address and let it roll. >> >> Hi Marc, >> >> When booting ACPI with X-Gene Mustang, I saw it hangs when EOI mode is >> enabled, should we have ACPI version for gic_check_eoimode as well? > > ACPI doesn't provide the size of the CPU interface, so you cannot > perform the same kind of check and bug workaround. I'm afraid you have > to fix your ACPI tables (which shouldn't be a problem since nobody is > using ACPI in production so far...). > Thanks, Marc.
We will go with your suggestion.
Regards, Duc Dang. > Thanks, > > M. > -- > Jazz is not dead. It just smells funny.
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