Messages in this thread | | | From | Chen-Yu Tsai <> | Date | Sun, 24 May 2015 23:55:22 +0800 | Subject | Re: [linux-sunxi] Re: [RFC 7/7] ARM: dts: sun9i: Add secure SRAM node used for MCPM SMP hotplug |
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On Wed, May 20, 2015 at 6:08 PM, Maxime Ripard <maxime.ripard@free-electrons.com> wrote: > On Thu, May 14, 2015 at 02:10:11PM +0800, Chen-Yu Tsai wrote: >> The A80 stores some magic flags in a portion of the secure SRAM. The >> BROM jumps directly to the software entry point set by the SMP code >> if the flags are set. This is required for CPU0 hotplugging. >> >> Signed-off-by: Chen-Yu Tsai <wens@csie.org> >> --- >> arch/arm/boot/dts/sun9i-a80.dtsi | 20 ++++++++++++++++++++ >> 1 file changed, 20 insertions(+) >> >> diff --git a/arch/arm/boot/dts/sun9i-a80.dtsi b/arch/arm/boot/dts/sun9i-a80.dtsi >> index 1507bd2a88f0..0695215634d4 100644 >> --- a/arch/arm/boot/dts/sun9i-a80.dtsi >> +++ b/arch/arm/boot/dts/sun9i-a80.dtsi >> @@ -366,6 +366,26 @@ >> */ >> ranges = <0 0 0 0x20000000>; >> >> + sram_b: sram@00020000 { >> + /* 256 KiB secure SRAM at 0x20000 */ >> + compatible = "mmio-sram"; >> + reg = <0x00020000 0x40000>; >> + > > We should probably add a property to that SRAM to tell the driver not > to access it if we're not booted in secure mode.
(CC-ing Heiko...)
That kind of puts architecture (ARM) dependent code into a platform driver. Furthermore, AFAIK there isn't a safe way to check if we're in secure mode or not. Checking SCR raises an undefined instruction exception in non-secure mode. Can the kernel handle that? I really don't understand this bit well.
> Otherwise, bad things might happen.
The kernel (or rather the bootloader) boots in secure mode by default, and we don't have any bootloader support to boot into non-secure mode ATM. Couldn't we have the bootloader mark the SRAM as disabled when booting into non-secure when we add that support?
ChenYu
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