linux-kernel - Re: [PATCH 1/1] arm64: Always provide "model name" in /proc/cpuinfo

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Message-ID: <15006378-af42-b029-f967-3f7230b64706@gmx.de>
Date:   Tue, 2 May 2017 18:28:40 +0200
From:   Heinrich Schuchardt <xypron.glpk@....de>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Will Deacon <will.deacon@....com>,
        Steve Capper <steve.capper@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Andre Przywara <andre.przywara@....com>,
        linux-kernel@...r.kernel.org, Julien Grall <julien.grall@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 1/1] arm64: Always provide "model name" in /proc/cpuinfo

On 05/02/2017 01:08 PM, Catalin Marinas wrote:
> On Tue, May 02, 2017 at 12:39:13AM +0200, Heinrich Schuchardt wrote:
>> There is no need to hide the model name in processes
>> that are not PER_LINUX32.
>>
>> So let us always provide a model name that is easily readable.
>>
>> Fixes: e47b020a323d ("arm64: Provide "model name" in /proc/cpuinfo for PER_LINUX32 tasks")
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
>> ---
>>  arch/arm64/kernel/cpuinfo.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
>> index b3d5b3e8fbcb..9ad9ddcd2f19 100644
>> --- a/arch/arm64/kernel/cpuinfo.c
>> +++ b/arch/arm64/kernel/cpuinfo.c
>> @@ -118,9 +118,8 @@ static int c_show(struct seq_file *m, void *v)
>>  		 * "processor".  Give glibc what it expects.
>>  		 */
>>  		seq_printf(m, "processor\t: %d\n", i);
>> -		if (compat)
>> -			seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",
>> -				   MIDR_REVISION(midr), COMPAT_ELF_PLATFORM);
>> +		seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",
>> +			   MIDR_REVISION(midr), COMPAT_ELF_PLATFORM);
>>  
>>  		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n",
>>  			   loops_per_jiffy / (500000UL/HZ),
> 
> Such patch seems to come up regularly:
> 
> https://patchwork.kernel.org/patch/9303311/
> 
> (and it usually gets rejected)
> 
Dear Catalin,

thank you for pointing me to the previous discussion. I understand that
adding model name in the current form would not provide sufficient
valuable information.

The real interesting thing in an ARM SOC is to see which CPU is A72,
A57, A53 or whatever.

This information is available from the device tree in the compatible
property of the individual CPUs
(/sys/firmware/devicetree/base/cpus/cpu@...ompatible), e.g.
compatible =3D "arm,cortex-a53", "arm,armv8";

I guess this information is the closest to the model name property on
other architectures that we can get.

Would exposing this information in /proc/cpuinfo as 'model name' make
sense to you?

Best regards

Heinrich