On Sat, Jul 18, 2015 at 6:54 AM, Kyle Huey <me@xxxxxxxxxxxx> wrote: > On Fri, Jul 17, 2015 at 4:59 PM, Thierry Reding > <thierry.reding@xxxxxxxxx> wrote: >> On Mon, Jul 13, 2015 at 10:35:45AM -0700, Kyle Huey wrote: >>> This patch modifies the device tree for tegra124 based devices to enable >>> the Cortex A15 PMU. The interrupt numbers are taken from NVIDIA TRM >>> DP-06905-001_v03p. This patch was tested on a Jetson TK1. >>> >>> Updated for proper ordering and to add interrupt-affinity values. >>> >>> Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx> >>> --- >>> arch/arm/boot/dts/tegra124.dtsi | 17 +++++++++++++---- >>> 1 file changed, 13 insertions(+), 4 deletions(-) >> >> Is there any way to test this? What are the effects of adding this? > > Yes. This enables the ARM PMU driver for the Cortex A15, which allows > one to use hardware performance counters via the perf_event_open API. > For a simple test program, see > https://github.com/khuey/perf-counter-test/. Without this patch, the > perf_event_open syscall will fail. With this patch, the program will > print out the performance counter value for each iteration of the > loop. (IIRC on the A15 the branch counter was removed, so you may want > to replace 0xD with 0x8 which counts instructions executed if you want > to see a non-zero number there). You also will see a message about > the PMU in the kernel log at startup after applying this patch. > > I have also tested this extensively (including the interrupt features > of the PMU) on a more complex program. > >> Does it enable using perf for profiling? > > I have not tested it, but I believe you can use perf without this > patch if you do not use features that require hardware performance > counter support. This patch would enable those features. > >>> diff --git a/arch/arm/boot/dts/tegra124.dtsi b/arch/arm/boot/dts/tegra124.dtsi >>> index 13cc7ca..de07d7e 100644 >>> --- a/arch/arm/boot/dts/tegra124.dtsi >>> +++ b/arch/arm/boot/dts/tegra124.dtsi >>> @@ -918,31 +918,40 @@ >>> #address-cells = <1>; >>> #size-cells = <0>; >>> >>> - cpu@0 { >>> + A15_0: cpu@0 { >>> device_type = "cpu"; >>> compatible = "arm,cortex-a15"; >>> reg = <0>; >>> }; >>> >>> - cpu@1 { >>> + A15_1: cpu@1 { >>> device_type = "cpu"; >>> compatible = "arm,cortex-a15"; >>> reg = <1>; >>> }; >>> >>> - cpu@2 { >>> + A15_2: cpu@2 { >>> device_type = "cpu"; >>> compatible = "arm,cortex-a15"; >>> reg = <2>; >>> }; >>> >>> - cpu@3 { >>> + A15_3: cpu@3 { >>> device_type = "cpu"; >>> compatible = "arm,cortex-a15"; >>> reg = <3>; >>> }; >>> }; >>> >>> + pmu { >>> + compatible = "arm,cortex-a15-pmu"; >>> + interrupts = <GIC_SPI 144 IRQ_TYPE_LEVEL_HIGH>, >>> + <GIC_SPI 145 IRQ_TYPE_LEVEL_HIGH>, >>> + <GIC_SPI 146 IRQ_TYPE_LEVEL_HIGH>, >>> + <GIC_SPI 147 IRQ_TYPE_LEVEL_HIGH>; >>> + interrupt-affinity = <&A15_0>, <&A15_1>, <&A15_2>, <&A15_3>; >> >> These labels look somewhat artificial to me, perhaps we could do >> something like the following instead? >> >> interrupt-affinity = <&{/cpus/cpu@0}>, ...; >> >> That's slightly more obvious and avoids the need to "invent" labels for >> the CPUs. >> >> No need to respin, I can fix that up when applying if nobody objects to >> using the alternative notation. >> >> Thierry > > I have no objections. I was not aware that the device tree syntax > supported that. FWIW I cargo-culted my way to victory from > vexpress-v2p-ca9.dts here. > > - Kyle Anything else I can do to help move this along? - Kyle -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
