[PATCH v2 1/3] dt-bindings: PCI: brcmstb: Add two optional props
Florian Fainelli
f.fainelli at gmail.com
Wed Apr 12 04:49:36 PDT 2023
On 4/12/2023 1:09 AM, Krzysztof Kozlowski wrote:
> On 11/04/2023 18:59, Jim Quinlan wrote:
>> Regarding "brcm,enable-l1ss":
>>
>> The Broadcom STB/CM PCIe HW -- a core that is also used by RPi SOCs --
>> requires the driver probe() to deliberately place the HW one of three
>> CLKREQ# modes:
>>
>> (a) CLKREQ# driven by the RC unconditionally
>> (b) CLKREQ# driven by the EP for ASPM L0s, L1
>> (c) Bidirectional CLKREQ#, as used for L1 Substates (L1SS).
>>
>> The HW+driver can tell the difference between downstream devices that
>> need (a) and (b), but does not know when to configure (c). Further, the
>> HW may cause a CPU abort on boot if guesses wrong regarding the need for
>> (c). So we introduce the boolean "brcm,enable-l1ss" property to indicate
>> that (c) is desired. Setting this property only makes sense when the
>> downstream device is L1SS-capable and the OS is configured to activate
>> this mode (e.g. policy==superpowersave).
>>
>> This property is already present in the Raspian version of Linux, but the
>> upstream driver implementaion that will follow adds more details and
>
> typo, implementation
>
>> discerns between (a) and (b).
>>
>> Regarding "brcm,completion-timeout-us"
>>
>> Our HW will cause a CPU abort if the L1SS exit time is longer than the
>> PCIe transaction completion abort timeout. We've been asked to make this
>> configurable, so we are introducing "brcm,completion-timeout-us".
>>
>> Signed-off-by: Jim Quinlan <jim2101024 at gmail.com>
>
> What happened here? Where is the changelog?
It is in the cover letter:
https://lore.kernel.org/all/20230411165919.23955-1-jim2101024@gmail.com/
but it does not look like the cover letter was copied to you or Rob.
--
Florian
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