linux-kernel - Re: [PATCH] ARM: tegra20: Store CPU "resettable" status in IRAM

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Message-ID: <54BD3E3E.2040801@wwwdotorg.org>
Date:	Mon, 19 Jan 2015 10:26:22 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Thierry Reding <thierry.reding@...il.com>,
	Dmitry Osipenko <digetx@...il.com>
CC:	Alexandre Courbot <gnurou@...il.com>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] ARM: tegra20: Store CPU "resettable" status in IRAM

On 01/19/2015 07:12 AM, Thierry Reding wrote:
> On Thu, Jan 15, 2015 at 01:58:57PM +0300, Dmitry Osipenko wrote:
>> Commit 7232398abc6a ("ARM: tegra: Convert PMC to a driver") changed tegra_resume()
>> location storing from late to early and, as a result, broke suspend on Tegra20.
>> PMC scratch register 41 is used by tegra LP1 resume code for retrieving stored
>> physical memory address of common resume function and in the same time used by
>> tegra20_cpu_shutdown() (shared by Tegra20 cpuidle driver and platform SMP code),
>> which is storing CPU1 "resettable" status. It implies strict order of scratch
>> register usage, otherwise resume function address is lost on Tegra20 after
>> disabling non-boot CPU's on suspend. Fix it by storing "resettable" status in
>> IRAM instead of PMC scratch register.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> Fixes: 7232398abc6a (ARM: tegra: Convert PMC to a driver)
>> Cc: <stable@...r.kernel.org> # v3.17+
>> ---
>>   arch/arm/mach-tegra/cpuidle-tegra20.c |  5 ++---
>>   arch/arm/mach-tegra/reset-handler.S   | 10 +++++++---
>>   arch/arm/mach-tegra/reset.h           |  4 ++++
>>   arch/arm/mach-tegra/sleep-tegra20.S   | 37 ++++++++++++++++++++---------------
>>   arch/arm/mach-tegra/sleep.h           |  4 ++++
>>   5 files changed, 38 insertions(+), 22 deletions(-)
>
> I'm leaning towards applying this. Stephen, Alex, Peter: any objections?

Hopefully this works out. I suppose it's unlikely anyone will be running 
code on the AVP upstrem, so any potential conflict with AVP's usage of 
IRAM isn't likely to occur.

__tegra20_cpu1_resettable_status_offset has a lot of _ at the start. 
Should the symbol be named more normally? I guess at least it's 
consistent with the existing very "underscory" 
__tegra_cpu_reset_handler_start.
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