linux-kernel - Re: [PATCH mvebu v2 06/10] clk: mvebu: armada-37xx-periph: Fix workaround for switching from L1 to L0

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Date:   Tue, 09 Feb 2021 17:58:31 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Michael Turquette <mturquette@...libre.com>,
        Pali Rohár <pali@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Marek Behún <kabel@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Tomasz Maciej Nowak <tmn505@...il.com>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Andre Heider <a.heider@...il.com>,
        Vladimir Vid <vladimir.vid@...tura.hr>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Gérald Kerma <gerald@....net>,
        Konstantin Porotchkin <kostap@...vell.com>
Subject: Re: [PATCH mvebu v2 06/10] clk: mvebu: armada-37xx-periph: Fix workaround for switching from L1 to L0

Quoting Pali Rohár (2021-01-14 04:40:28)
> When CPU frequency is at 250 MHz and set_rate() is called with 500 MHz (L1)
> quickly followed by a call with 1 GHz (L0), the CPU does not necessarily
> stay in L1 for at least 20ms as is required by Marvell errata.
> 
> This situation happens frequently with the ondemand cpufreq governor and
> can be also reproduced with userspace governor. In most cases it causes CPU
> to crash.
> 
> This change fixes the above issue and ensures that the CPU always stays in
> L1 for at least 20ms when switching from any state to L0.
> 
> Signed-off-by: Marek Behún <kabel@...nel.org>
> Signed-off-by: Pali Rohár <pali@...nel.org>
> Fixes: 61c40f35f5cd ("clk: mvebu: armada-37xx-periph: Fix switching CPU rate from 300Mhz to 1.2GHz")
> Cc: stable@...r.kernel.org
> ---

Acked-by: Stephen Boyd <sboyd@...nel.org>