Subject: Re: [RESEND PATCH 0/1] Fix the "hard LOCKUP" when running a heavy
 loading
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
References: <1446538209-13490-1-git-send-email-wxt@rock-chips.com>
 <20151103111437.GU8644@n2100.arm.linux.org.uk>
Cc: Caesar Wang <wxt@rock-chips.com>,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        Heiko Stuebner <heiko@sntech.de>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>, sjg@chromium.org,
        Stephen Boyd <sboyd@codeaurora.org>, dianders@chromium.org,
        linux-kernel@vger.kernel.org, Nadav Haklai <nadavh@marvell.com>,
        linux-rockchip@lists.infradead.org, cwz@rock-chips.com,
        Jonathan Stone <j.stone@samsung.com>,
        Gregory CLEMENT <gregory.clement@free-electrons.com>,
        linux-arm-kernel@lists.infradead.org, hl@rock-chips.com
From: "Huang, Tao" <huangtao@rock-chips.com>
Message-ID: <5638A1C6.30200@rock-chips.com>
Date: Tue, 3 Nov 2015 20:00:06 +0800
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Hello Russell:

在 2015年11月03日 19:14, Russell King - ARM Linux 写道:
> On Tue, Nov 03, 2015 at 04:10:08PM +0800, Caesar Wang wrote:
>> As the Russell said:
>> "in other words, which can be handled by updating a control register in
>> the firmware or boot loader"
>> Maybe the better solution is in firmware.
> 
> The full quote is:
> 
> "I think we're at the point where we start insisting that workarounds
> which are simple enable/disable feature bit operations (in other words,
> which can be handled by updating a control register in the firmware or
> boot loader) must be done that way, and we are not going to add such
> workarounds to the kernel anymore."
> 
> The position hasn't changed.  Workarounds such as this should be handled
> in the firmware/boot loader before control is passed to the kernel.
> 
> The reason is very simple: if the C compiler can generate code which
> triggers the bug, it can generate code which triggers the bug in the
> boot loader.  So, the only place such workarounds can be done is before
> any C code gets executed.  Putting such workarounds in the kernel is
> completely inappropriate.

I agree with your reason for CPU0. But how about CPU1~3 if we don't use
any firmware such as ARM Trusted Firmware to take control of CPU power
on? If the CPU1~3 will run on Linux when its first instruction is running?

BTW I don't want to argue with you the workaround is right or wrong
because I know the errata just happen on r0p0 not r0p1.

> 
> Sorry, I'm not going to accept this workaround into the kernel.

It seems we should introduce some code outside the kernel to do such
initialization?

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