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| /openbmc/linux/arch/arm64/boot/dts/allwinner/ |
| H A D | sun50i-a64.dtsi | 6b832a14 Tue Nov 05 05:06:51 CST 2019 Andre Przywara <andre.przywara@arm.com> arm64: dts: allwinner: a64: Re-add PMU node
As it was found recently, the Performance Monitoring Unit (PMU) on the
Allwinner A64 SoC was not generating (the right) interrupts. With the
SPI numbers from the manual the kernel did not receive any overflow
interrupts, so perf was not happy at all.
It turns out that the numbers were just off by 4, so the PMU interrupts
are from 148 to 151, not from 152 to 155 as the manual describes.
This was found by playing around with U-Boot, which typically does not
use interrupts, so the GIC is fully available for experimentation:
With *every* PPI and SPI enabled, an overflowing PMU cycle counter was
found to set a bit in one of the GICD_ISPENDR registers, with careful
counting this was determined to be number 148.
Tested with perf record and perf top on a Pine64-LTS. Also tested with
tasksetting to every core to confirm the assignment between IRQs and
cores.
This somewhat "revert-fixes" commit ed3e9406bcbc ("arm64: dts: allwinner:
a64: Drop PMU node").
Fixes: 34a97fcc71c2 ("arm64: dts: allwinner: a64: Add PMU node")
Fixes: ed3e9406bcbc ("arm64: dts: allwinner: a64: Drop PMU node")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
6b832a14 Tue Nov 05 05:06:51 CST 2019 Andre Przywara <andre.przywara@arm.com> arm64: dts: allwinner: a64: Re-add PMU node
As it was found recently, the Performance Monitoring Unit (PMU) on the
Allwinner A64 SoC was not generating (the right) interrupts. With the
SPI numbers from the manual the kernel did not receive any overflow
interrupts, so perf was not happy at all.
It turns out that the numbers were just off by 4, so the PMU interrupts
are from 148 to 151, not from 152 to 155 as the manual describes.
This was found by playing around with U-Boot, which typically does not
use interrupts, so the GIC is fully available for experimentation:
With *every* PPI and SPI enabled, an overflowing PMU cycle counter was
found to set a bit in one of the GICD_ISPENDR registers, with careful
counting this was determined to be number 148.
Tested with perf record and perf top on a Pine64-LTS. Also tested with
tasksetting to every core to confirm the assignment between IRQs and
cores.
This somewhat "revert-fixes" commit ed3e9406bcbc ("arm64: dts: allwinner:
a64: Drop PMU node").
Fixes: 34a97fcc71c2 ("arm64: dts: allwinner: a64: Add PMU node")
Fixes: ed3e9406bcbc ("arm64: dts: allwinner: a64: Drop PMU node")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
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