[PATCH 2/2] ARM: bcm2835: Add devicetree for the Raspberry Pi 3.

Eric Anholt
2016-03-04T19:39:06Z

Mark Rutland <mark.rutland@arm.com> writes:

> On Fri, Mar 04, 2016 at 10:55:03AM -0800, Eric Anholt wrote:
>> Mark Rutland <mark.rutland@arm.com> writes:
>>
>> > On Fri, Mar 04, 2016 at 10:39:29AM -0800, Eric Anholt wrote:
>> >> For now this doesn't support the new hardware present on the Pi 3 (BT,
>> >> wifi, GPIO expander). Since the GPIO expander isn't supported, we
>> >> also don't have the LEDs like the other board files do.
>> >>
>> >> Signed-off-by: Eric Anholt <eric@anholt.net>
>> >> ---
>> >> arch/arm/boot/dts/Makefile | 3 +-
>> >> arch/arm/boot/dts/bcm2837-rpi-3-b.dts | 22 ++++++++++++
>> >> arch/arm/boot/dts/bcm2837.dtsi | 68 +++++++++++++++++++++++++++++++++++
>> >> 3 files changed, 92 insertions(+), 1 deletion(-)
>> >> create mode 100644 arch/arm/boot/dts/bcm2837-rpi-3-b.dts
>> >> create mode 100644 arch/arm/boot/dts/bcm2837.dtsi
>> >
>> >> + timer {
>> >> + compatible = "arm,armv7-timer";
>> >> + interrupt-parent = <&local_intc>;
>> >> + interrupts = <0>, // PHYS_SECURE_PPI
>> >> + <1>, // PHYS_NONSECURE_PPI
>> >> + <3>, // VIRT_PPI
>> >> + <2>; // HYP_PPI
>> >> + always-on;
>> >> + };
>> >
>> > Are the CPUs in an always-on power domain? Or is it jsut that the kernel
>> > doesn't perform power management of CPUs?
>> >
>> > The always-on proeprty is only intended for the former.
>>
>> The kernel doesn't get to do power management of CPUs. We only have
>> control of power domains through the firmware, and the firmware's
>> keeping the CPU domain on.
>
> So there is no way that the CPUs could request for the firmare to place
> them in a state where the timer would lose context (but other events
> coukd wake them up), even if they don't do that today?

I don't see any mechanism in the RPi firmware for the ARM to request
suspend or anything like that. Enabling something like that would
definitely require an updated DT, to enable a driver that talks to the
firmware to make requests like that.

(Note that this is the same timer setup we have in bcm2836.dtsi)
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