linux-kernel - Re: [PATCH v3 4/6] ARM64: arch_timer: configure and enable event stream

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Message-ID: <20130821175227.GH1653@mudshark.cambridge.arm.com>
Date:	Wed, 21 Aug 2013 18:52:27 +0100
From:	Will Deacon <will.deacon@....com>
To:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v3 4/6] ARM64: arch_timer: configure and enable event
 stream

Hi Sudeep,

On Tue, Aug 20, 2013 at 06:08:46PM +0100, Sudeep KarkadaNagesha wrote:
> From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
> 
> This patch configures the event stream frequency and enables it.
> It also adds the hwcaps as well as compat-specific definitions to
> the user to detect this event stream feature.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Signed-off-by: Will Deacon <will.deacon@....com>
> [sudeep: moving ARM/ARM64 changes into separate patches]
> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
> ---
>  arch/arm64/include/asm/arch_timer.h | 15 +++++++++++++--
>  arch/arm64/include/asm/hwcap.h      |  7 ++++++-
>  arch/arm64/include/uapi/asm/hwcap.h |  1 +
>  arch/arm64/kernel/setup.c           |  6 ++++++
>  4 files changed, 26 insertions(+), 3 deletions(-)
> 
> Hi Will,
> 
> This is modified version enabling timer event stream hwcap compat dynamically.
> Let me know if this looks fine.

Looks pretty good to me, one minor comment:

> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index add6ea6..91af65a 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -60,6 +60,11 @@ EXPORT_SYMBOL(processor_id);
>  unsigned int elf_hwcap __read_mostly;
>  EXPORT_SYMBOL_GPL(elf_hwcap);
>  
> +#ifdef CONFIG_COMPAT
> +unsigned int compat_dyn_elf_hwcap __read_mostly = 0;
> +EXPORT_SYMBOL_GPL(compat_dyn_elf_hwcap);
> +#endif

Given that the arch timer is the only user of this at the moment, and cannot
be built as a module, I don't think we should bother exporting the symbol
until it's actually required.

Will
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