linux-kernel - Re: [PATCH v2 3/3] ARM: tegra: set CPU reset handler with firmware op

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Date:	Fri, 14 Jun 2013 17:54:59 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	Joseph Lo <josephl@...dia.com>,
	Karan Jhavar <kjhavar@...dia.com>,
	Varun Wadekar <vwadekar@...dia.com>,
	Chris Johnson <CJohnson@...dia.com>,
	Matthew Longnecker <MLongnecker@...dia.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Dave Martin <Dave.Martin@....com>,
	Jassi Brar <jassisinghbrar@...il.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/3] ARM: tegra: set CPU reset handler with firmware op

On Fri, Jun 14, 2013 at 4:23 AM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 06/13/2013 03:12 AM, Alexandre Courbot wrote:
>> Use a firmware operation to set the CPU reset handler and only resort to
>> doing it ourselves if there is none defined.
>>
>> This supports the booting of secondary CPUs on devices using a TrustZone
>> secure monitor.
>
>> diff --git a/arch/arm/mach-tegra/reset.c b/arch/arm/mach-tegra/reset.c
>
>> +     err = call_firmware_op(set_cpu_boot_addr, 0, reset_address);
>> +     switch (err) {
>> +     case -ENOSYS:
>> +             tegra_cpu_reset_handler_set(reset_address);
>> +             /* pass-through */
>
> Rather than detecting -ENOSYS and falling back to the custom
> tegra_cpu_reset_handler_set(), does it make sense to plug in
> tegra_cpu_reset_handler_set as the firmware op when there is no secure
> firmware detected? That way, this code wouldn't need the special case;
> that would be isolated to firmware.c.

Mmmm I admit I just followed what Exynos did without thinking much
about it. I don't see any reason why your suggestion wouldn't work,
but on second thought tegra_cpu_reset_handler_set() is not a firmware
operation - wouldn't it be unexpected (and maybe confusing) to have it
called through call_firmware_op()?

Alex.
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