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mvebu: armada-37xx: add patch to forbid cpufreq for 1.2 GHz

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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 <pepe.schlehofer@gmail.com>
(cherry picked from commit d379476817)
This commit is contained in:
Josef Schlehofer
2021-07-27 13:22:31 +02:00
committed by Hauke Mehrtens
parent b254bd697d
commit f407b2f43c
1 changed files with 39 additions and 0 deletions
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39
target/linux/mvebu/patches-5.4/100-cpufreq-armada-37xx-forbid-cpufreq-for-1.2-GHz-variant.patch Normal file
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@@ -0,0 +1,39 @@
From: =?utf-8?q?Marek_Beh=C3=BAn?= <kabel@kernel.org>
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 <kabel@kernel.org>
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} },