Re: [PATCH v2 2/4] dt-bindings: Add 'slot-power-limit-milliwatt' PCIe port property

Rob Herring
2022-03-24T20:48:44Z

On Wed, Mar 02, 2022 at 03:57:31PM +0100, Pali Rohár wrote:
> This property specifies slot power limit in mW unit. It is a form-factor
> and board specific value and must be initialized by hardware.
>
> Some PCIe controllers delegate this work to software to allow hardware
> flexibility and therefore this property basically specifies what should
> host bridge program into PCIe Slot Capabilities registers.
>
> The property needs to be specified in mW unit instead of the special format
> defined by Slot Capabilities (which encodes scaling factor or different
> unit). Host drivers should convert the value from mW to needed format.
>
> Signed-off-by: Pali Rohár <pali@kernel.org>
> Signed-off-by: Marek Behún <kabel@kernel.org>
>
> ---
> This change was already accepted into dt-schema repo by Rob Herring:
> https://github.com/devicetree-org/dt-schema/pull/66

Which is the definitive source for it. pci.txt should shrink or be
removed, not added to.

> ---
> Documentation/devicetree/bindings/pci/pci.txt | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt
> index 6a8f2874a24d..b0cc133ed00d 100644
> --- a/Documentation/devicetree/bindings/pci/pci.txt
> +++ b/Documentation/devicetree/bindings/pci/pci.txt
> @@ -32,6 +32,12 @@ driver implementation may support the following properties:
> root port to downstream device and host bridge drivers can do programming
> which depends on CLKREQ signal existence. For example, programming root port
> not to advertise ASPM L1 Sub-States support if there is no CLKREQ signal.
> +- slot-power-limit-milliwatt:
> + If present, this property specifies slot power limit in milliwatts. Host
> + drivers can parse this property and use it for programming Root Port or host
> + bridge, or for composing and sending PCIe Set_Slot_Power_Limit messages
> + through the Root Port or host bridge when transitioning PCIe link from a
> + non-DL_Up Status to a DL_Up Status.
>
> PCI-PCI Bridge properties
> -------------------------
> --
> 2.20.1