linux-kernel - Re: [PATCH v2 2/3] Documentation: sysfs: Document Broadcom STB memc sysfs knobs

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Message-ID: <2dffc393-b86c-17e2-8c11-bdd9504366c5@linaro.org>
Date:   Tue, 26 Jul 2022 11:34:55 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] Documentation: sysfs: Document Broadcom STB memc
 sysfs knobs

On 25/07/2022 18:07, Florian Fainelli wrote:
> On 7/23/22 10:59, Krzysztof Kozlowski wrote:
>> On 22/07/2022 22:10, Florian Fainelli wrote:
>>> Document the "srpd" and "frequency" sysfs attributes exposed by
>>> the brcmstb_memc driver.
>>>
>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>> ---
>>>  .../ABI/testing/sysfs-platform-brcmstb-memc       | 15 +++++++++++++++
>>>  1 file changed, 15 insertions(+)
>>>  create mode 100644 Documentation/ABI/testing/sysfs-platform-brcmstb-memc
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-platform-brcmstb-memc b/Documentation/ABI/testing/sysfs-platform-brcmstb-memc
>>> new file mode 100644
>>> index 000000000000..2bf0f58e412c
>>> --- /dev/null
>>> +++ b/Documentation/ABI/testing/sysfs-platform-brcmstb-memc
>>> @@ -0,0 +1,15 @@
>>> +What:		/sys/devices/platform/*/*/*/*/srpd
>>
>> That's a lot of */. Are you sure it is correct path? Didn't you include
>> here some driver-related path components? Can you paste in email full
>> path as an example?
> 
> Yes this is the correct path:
> 
> /sys/devices/platform/rdb/rdb:memory_controllers/rdb:memory_controllers:memc@...902000.memc-ddr/
> 
> the 'rdb' node is our top level bus node, the 'rdb:memory_controllers' is an encapsulating node that groups all of the possible memory controllers in a system (there can be between 1 and 3), the rdb:memory_controllers@0 is the first of those memory controller and finally the 9902000.memc-ddr is the sub-node that contains the register controls of interest, since the memory controller aggregates different functions (arbitration, configuration, statistics, DDR PHY SHIM layer, etc.). Maybe I should provide a more complete binding while I am it.

The path should be much more specific so include at least:
rdb/rdb:memory_controllers/rdb:memory_controllers:memc@*/
(or some variations of it if pieces of name change)

However looking at the driver, this is regular platform driver, thus  it
will appear as:
/sys/bus/platform/9902000.memc-ddr


Best regards,
Krzysztof