Hello! The armada-37xx-cpufreq driver changes base CPU speed from 1000 MHz to 800 MHz on EspressoBIN and Turris MOX. The commit message in patch 2/10 explains why and how can this be discovered.
That patch 2/10 led us to discover another bug, in the SOC itself, that causes the CPU to behave weirdly when frequency changes to 1 GHz. A similar erratum is documented by Marvell but only for systems where base frequency is 1.2 GHz. We've discovered that to make cpufreq scaling stable on Armada 3720 systems with base frequency 1 GHz, we also have to set voltage levels for L0 and L1 loads to at least 1108 mV. We were led to this by patch we found in Marvell kernel fork. Fix is in the patch 4/10. https://github.com/MarvellEmbeddedProcessors/linux-marvell/commit/dc33b62c90696afb6adc7dbcc4ebbd48bedec269 During fixing this voltage issue for 1 GHz we discovered another bug in armada-37xx-cpufreq driver that causes CPU instability. Erratum for VDD stabilization was improperly implemented, details are in patch 6/10. This patch series is also available in my git tree in branch a3720-cpufreq-issues: https://git.kernel.org/pub/scm/linux/kernel/git/pali/linux.git/log/?h=a3720-cpufreq-issues We have tested this patch series on Espressobin v5 and Turris MOX boards. If you have other Armada 3720 boards (Espressobin v5/v7, uDPU, Devel Board, ...) then it will be nice to do an additional tests and check if instability issues are finally fixed. There is a discussion on armbian forum that Espressobin v7 is unstable when running at 1 GHz and in this thread was also mentioned above voltage patch from Marvell kernel fork: https://forum.armbian.com/topic/10429-how-to-make-espressobin-v7-stable/ Marek & Pali Marek Behún (3): arm64: dts: marvell: armada-37xx: add syscon compatible to NB clk node cpufreq: armada-37xx: Fix setting TBG parent for load levels clk: mvebu: armada-37xx-periph: remove .set_parent method for CPU PM clock Pali Rohár (7): cpufreq: armada-37xx: Fix the AVS value for loads L0 and L1 clk: mvebu: armada-37xx-periph: Fix switching CPU freq from 250 Mhz to 1 GHz clk: mvebu: armada-37xx-periph: Fix workaround for switching from L1 to L0 cpufreq: armada-37xx: Fix driver cleanup when registration failed cpufreq: armada-37xx: Fix determining base CPU frequency cpufreq: armada-37xx: Remove cur_frequency variable cpufreq: armada-37xx: Fix module unloading arch/arm64/boot/dts/marvell/armada-37xx.dtsi | 3 +- drivers/clk/mvebu/armada-37xx-periph.c | 83 ++++++++------- drivers/cpufreq/armada-37xx-cpufreq.c | 100 ++++++++++++++----- 3 files changed, 124 insertions(+), 62 deletions(-) -- 2.20.1
