Re: [PATCH v1 1/3] dt-bindings: PCI: brcmstb: Add two optional props

Florian Fainelli
2023-04-06T18:53:26Z

On 4/6/23 11:34, Krzysztof Kozlowski wrote:
> On 06/04/2023 14:46, Jim Quinlan wrote:
>> Regarding "brcm,enable-l1ss":
>>
>> The Broadcom STB/CM PCIe HW -- which is also used by RPi SOCs -- requires
>> the driver probe to configure one of three clkreq# modes:
>>
>> (a) clkreq# driven by the RC
>> (b) clkreq# driven by the EP for ASPM L0s, L1
>> (c) bidirectional clkreq#, as used for L1 Substates (L1SS).
>>
>> The HW can tell the difference between (a) and (b), but does not know
>> when to configure (c). Further, the HW will 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. This
>> property is already present in the Raspian version of Linux, but the
>> driver implementaion that will follow adds more details and discerns
>> between (a) and (b).
>>
>> Regarding "brcm,completion-timeout-msecs"
>>
>> Our HW will cause a CPU abort if the L1SS exit time is longer than the
>> completion abort timeout. We've been asked to make this configurable, so
>> we are introducing "brcm,completion-abort-msecs".
>>
>> Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
>> ---
>> .../devicetree/bindings/pci/brcm,stb-pcie.yaml | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
>> index 7e15aae7d69e..ef4ccc05b258 100644
>> --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
>> +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
>> @@ -64,6 +64,18 @@ properties:
>>
>> aspm-no-l0s: true
>>
>> + brcm,enable-l1ss:
>> + description: Indicates that the downstream device is L1SS
>> + capable and L1SS is desired, e.g. by setting
>> + CONFIG_PCIEASPM_POWER_SUPERSAVE=y. Note that CLKREQ#
>
> How does CONFIG_PCIEASPM_POWER_SUPERSAVE apply to *BSD?

In other words, there should be no OS/Linux specific comments in a
Device Tree binding, which would be a friendlier and nicer way of
providing the same feedback.
--
Florian