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

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Message-ID: <3d29b8fc-f183-5883-edc0-cde55b76e4fd@gmail.com>
Date:   Mon, 25 Jul 2022 09:07:40 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 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.

> 
>> +Date:		July 2022
>> +KernelVersion:	5.21
>> +Contact:	Florian Fainelli <f.fainelli@...il.com>
>> +Description:
>> +		Self Refresh Power Down (SRPD) inactivity timeout counted in
>> +		internal DDR controller clock cycles. Possible values range
>> +		from 0 (disable inactivity timeout) to 65535 (0xffff).
> 
> Using hex suggests one should write there hex? If so, skip decimal...
> You describe the user interface, not hardware registers.

Fair enough.
-- 
Florian