linux-kernel - Re: [PATCH 3/6] ARM: Add Krait L2 accessor functions

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Date:	Mon, 28 Oct 2013 18:21:57 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Mark Rutland <mark.rutland@....com>
CC:	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/6] ARM: Add Krait L2 accessor functions

On 10/28/13 18:19, Mark Rutland wrote:
> On Tue, Oct 29, 2013 at 12:31:27AM +0000, Stephen Boyd wrote:
>> Qualcomm's Krait CPUs have a handful of L2 cache controller
>> registers that live behind a cp15 based indirection register.
>> First you program the indirection register (l2cpselr) to point
>> the L2 'window' register (l2cpdr) at what you want to read/write.
>> Then you read/write the 'window' register to do what you want.
>> The l2cpselr register is not banked per-cpu so we must lock
>> around accesses to it to prevent other CPUs from re-pointing
>> l2cpdr underneath us.
>>
>> Cc: Russell King <linux@....linux.org.uk>
>> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
>> ---
>>  arch/arm/common/Kconfig                   |  3 ++
>>  arch/arm/common/Makefile                  |  1 +
>>  arch/arm/common/krait-l2-accessors.c      | 52 +++++++++++++++++++++++++++++++
>>  arch/arm/include/asm/krait-l2-accessors.h | 20 ++++++++++++
>>  4 files changed, 76 insertions(+)
>>  create mode 100644 arch/arm/common/krait-l2-accessors.c
>>  create mode 100644 arch/arm/include/asm/krait-l2-accessors.h
> [...]
>
>> +void set_l2_indirect_reg(u32 addr, u32 val)
>> +{
>> +	unsigned long flags;
>> +
>> +	raw_spin_lock_irqsave(&krait_l2_lock, flags);
>> +
>> +	asm volatile ("mcr p15, 3, %0, c15, c0, 6" : : "r" (addr));
>> +	isb();
>> +	asm volatile ("mcr p15, 3, %0, c15, c0, 7" : : "r" (val));
>> +	isb();
>> +
>> +	raw_spin_unlock_irqrestore(&krait_l2_lock, flags);
>> +}
>> +EXPORT_SYMBOL(set_l2_indirect_reg);
> It might be worth commmenting inline as to what register each of these is
> accessing. Inevitably the commit message will become harder to find and
> associate with the code over time.
>
> Similarly for get_l2_indirect_reg.

Do you mean with the "@" syntax in the assembly? The 80-character limit
is out to get me.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

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