Re: [PATCH v2 04/21] ARM: tegra: update DTs to expose legacy interrupt controller

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On 2015-01-08 10:41, Thierry Reding wrote:
On Wed, Jan 07, 2015 at 05:42:39PM +0000, Marc Zyngier wrote:
Describe the legacy interrupt controller in every tegra DTSI files,
and make it the parent of most interrupts.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
 arch/arm/boot/dts/tegra114.dtsi | 16 +++++++++++++++-
 arch/arm/boot/dts/tegra124.dtsi | 16 +++++++++++++++-
 arch/arm/boot/dts/tegra20.dtsi  | 15 ++++++++++++++-
 arch/arm/boot/dts/tegra30.dtsi  | 16 +++++++++++++++-
 4 files changed, 59 insertions(+), 4 deletions(-)


I've updated the patch to reflect the requested changes. See below for the few contentious points:

[...]

@@ -134,6 +134,19 @@
 		      <0x50046000 0x2000>;
 		interrupts = <GIC_PPI 9
 			(GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_HIGH)>;
+		interrupt-parent = <&gic>;

Is this allowed? It makes the GIC its own parent. I guess we need it to
stop a loop from GIC -> LIC -> GIC, but it doesn't look quite right.

This seems to be the expected construct to override a parent interrupt controller. Actually, this is already what happens when you have a single interrupt-controller and a global interrupt-parent property.

[...]

 	timer@60005000 {
@@ -766,5 +779,6 @@
 				(GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
 			<GIC_PPI 10
 				(GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>;
+		interrupt-parent = <&gic>;

Why does this get to have a non-default parent?

The per-cpu timers are using PPIs. As such,. they are not routed through the LIC, but are wired to the GIC instead.

[...]

 	timer@60005000 {
 		compatible = "nvidia,tegra20-timer";
 		reg = <0x60005000 0x60>;

Why doesn't the Tegra timer get to keep the GIC as parent like for
Tegra114 and Tegra124? Instead I see that the Cortex-A9 TWD timer gets
to keep the parent instead.

The Tegra timer is using SPI (and can probably be used as a wake-up source). As such, it is connected to the LIC, not to the GIC.

Per-CPU timers (arch timer for A15 and TWD for A9) are all using PPIs, and are directly wired to the GIC.

[...]

 	timer@60005000 {
 		compatible = "nvidia,tegra30-timer", "nvidia,tegra20-timer";
 		reg = <0x60005000 0x400>;

Like for Tegra20, the Tegra timer is now switched to the LIC as parent.

Which, in my understanding, is the right thing to do. Unless I missed something obvious about this?

Thanks,

        M.
--
Fast, cheap, reliable. Pick two.
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