linux-kernel - Re: [PATCH v2] EDAC: Add ARM64 EDAC

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Date:	Fri, 23 Oct 2015 09:41:22 +0800
From:	Hanjun Guo <guohanjun@...wei.com>
To:	Brijesh Singh <brijeshkumar.singh@....com>,
	Andre Przywara <andre.przywara@....com>,
	<linux-arm-kernel@...ts.infradead.org>
CC:	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<dougthompson@...ssion.com>, <bp@...en8.de>,
	<mchehab@....samsung.com>, <devicetree@...r.kernel.org>,
	<arnd@...db.de>, <linux-kernel@...r.kernel.org>,
	<linux-edac@...r.kernel.org>, Huxinwei <huxinwei@...wei.com>
Subject: Re: [PATCH v2] EDAC: Add ARM64 EDAC

Hi Brijesh,

On 2015/10/22 22:46, Brijesh Singh wrote:
> Hi Andre,
>
> On 10/21/2015 06:52 PM, Andre Przywara wrote:
>> On 21/10/15 21:41, Brijesh Singh wrote:
>>> Add support for Cortex A57 and A53 EDAC driver.
>> Hi Brijesh,
>>
>> thanks for the quick update! Some comments below.
>>
>>> Signed-off-by: Brijesh Singh <brijeshkumar.singh@....com>
>>> CC: robh+dt@...nel.org
>>> CC: pawel.moll@....com
>>> CC: mark.rutland@....com
>>> CC: ijc+devicetree@...lion.org.uk
>>> CC: galak@...eaurora.org
>>> CC: dougthompson@...ssion.com
>>> CC: bp@...en8.de
>>> CC: mchehab@....samsung.com
>>> CC: devicetree@...r.kernel.org
>>> CC: guohanjun@...wei.com
>>> CC: andre.przywara@....com
>>> CC: arnd@...db.de
>>> CC: linux-kernel@...r.kernel.org
>>> CC: linux-edac@...r.kernel.org
>>> ---
>>>
>>> v2:
>>> * convert into generic arm64 edac driver
>>> * remove AMD specific references from dt binding
>>> * remove poll_msec property from dt binding
>>> * add poll_msec as a module param, default is 100ms
>>> * update copyright text
>>> * define macro mnemonics for L1 and L2 RAMID
>>> * check L2 error per-cluster instead of per core
>>> * update function names
>>> * use get_online_cpus() and put_online_cpus() to make L1 and L2 register 
>>>   read hotplug-safe
>>> * add error check in probe routine
>>>
>>>  .../devicetree/bindings/edac/armv8-edac.txt        |  15 +
>>>  drivers/edac/Kconfig                               |   6 +
>>>  drivers/edac/Makefile                              |   1 +
>>>  drivers/edac/cortex_arm64_edac.c                   | 457 +++++++++++++++++++++
>>>  4 files changed, 479 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/edac/armv8-edac.txt
>>>  create mode 100644 drivers/edac/cortex_arm64_edac.c
>>>
>>> diff --git a/Documentation/devicetree/bindings/edac/armv8-edac.txt b/Documentation/devicetree/bindings/edac/armv8-edac.txt
>>> new file mode 100644
>>> index 0000000..dfd128f
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/edac/armv8-edac.txt
>>> @@ -0,0 +1,15 @@
>>> +* ARMv8 L1/L2 cache error reporting
>>> +
>>> +On ARMv8, CPU Memory Error Syndrome Register and L2 Memory Error Syndrome
>>> +Register can be used for checking L1 and L2 memory errors.
>>> +
>>> +The following section describes the ARMv8 EDAC DT node binding.
>>> +
>>> +Required properties:
>>> +- compatible: Should be "arm,armv8-edac"
>>> +
>>> +Example:
>>> +	edac {
>>> +		compatible = "arm,armv8-edac";
>>> +	};
>>> +
>> So if there is nothing in here, why do we need the DT binding at all (I
>> think Mark hinted at that already)?
>> Can't we just use the MIDR as already suggested by others?
>> Secondly, armv8-edac is wrong here, as this feature is ARM-Cortex
>> specific and not architectural.
>>
> Yes, I was going with Mark suggestion to remove DT binding but then came across these cases which kind of hinted to keep DT binding:
>
> * Without DT binding, the driver will always be loaded on arm64 unless its blacklisted.
> * Its possible that other SoC's might handle single-bit and double-bit errors differently compare to 
>   Seattle platform. In Seattle platform both errors are handled by firmware but if other SoC 
>   wants OS to handle these errors then they might need DT binding to provide the irq numbers etc.

I totally agree with you here,  thanks for putting them together.
Different SoCs may handle the error in different ways, we need
bindings to specialize them, irq number is a good example :)

Thanks
Hanjun

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