From d3794768177293f584cc74f90c921276793da1e7 Mon Sep 17 00:00:00 2001 From: Josef Schlehofer Date: Tue, 27 Jul 2021 13:22:31 +0200 Subject: [PATCH] mvebu: armada-37xx: add patch to forbid cpufreq for 1.2 GHz This patch is backported from linux-arm-kernel [1] to improve situation, when it was reported that 1.2 GHz variant is unstable with DFS. It waits to be accepted upstream, however, it waits for Marvell people to respond. [1] https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210630225601.6372-1-kabel@kernel.org/ Signed-off-by: Josef Schlehofer --- ...x-forbid-cpufreq-for-1.2-GHz-variant.patch | 39 +++++++++++++++++++ 1 file changed, 39 insertions(+) create mode 100644 target/linux/mvebu/patches-5.4/100-cpufreq-armada-37xx-forbid-cpufreq-for-1.2-GHz-variant.patch diff --git a/target/linux/mvebu/patches-5.4/100-cpufreq-armada-37xx-forbid-cpufreq-for-1.2-GHz-variant.patch b/target/linux/mvebu/patches-5.4/100-cpufreq-armada-37xx-forbid-cpufreq-for-1.2-GHz-variant.patch new file mode 100644 index 0000000000..6a5b8220f8 --- /dev/null +++ b/target/linux/mvebu/patches-5.4/100-cpufreq-armada-37xx-forbid-cpufreq-for-1.2-GHz-variant.patch @@ -0,0 +1,39 @@ +From: =?utf-8?q?Marek_Beh=C3=BAn?= +Subject: [PATCH v2] cpufreq: armada-37xx: forbid cpufreq for 1.2 GHz variant +Date: Thu, 1 Jul 2021 00:56:01 +0200 + +The 1.2 GHz variant of the Armada 3720 SOC is unstable with DVFS: when +the SOC boots, the WTMI firmware sets clocks and AVS values that work +correctly with 1.2 GHz CPU frequency, but random crashes occur once +cpufreq driver starts scaling. + +We do not know currently what is the reason: +- it may be that the voltage value for L0 for 1.2 GHz variant provided + by the vendor in the OTP is simply incorrect when scaling is used, +- it may be that some delay is needed somewhere, +- it may be something else. + +The most sane solution now seems to be to simply forbid the cpufreq +driver on 1.2 GHz variant. + +Signed-off-by: Marek Behún +Fixes: 92ce45fb875d ("cpufreq: Add DVFS support for Armada 37xx") +--- + drivers/cpufreq/armada-37xx-cpufreq.c | 6 +++++- + 1 file changed, 5 insertions(+), 1 deletion(-) + +--- a/drivers/cpufreq/armada-37xx-cpufreq.c ++++ b/drivers/cpufreq/armada-37xx-cpufreq.c +@@ -102,7 +102,11 @@ struct armada_37xx_dvfs { + }; + + static struct armada_37xx_dvfs armada_37xx_dvfs[] = { +- {.cpu_freq_max = 1200*1000*1000, .divider = {1, 2, 4, 6} }, ++ /* ++ * The cpufreq scaling for 1.2 GHz variant of the SOC is currently ++ * unstable because we do not know how to configure it properly. ++ */ ++ /* {.cpu_freq_max = 1200*1000*1000, .divider = {1, 2, 4, 6} }, */ + {.cpu_freq_max = 1000*1000*1000, .divider = {1, 2, 4, 5} }, + {.cpu_freq_max = 800*1000*1000, .divider = {1, 2, 3, 4} }, + {.cpu_freq_max = 600*1000*1000, .divider = {2, 4, 5, 6} },