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From: Rob Herring <robh+dt@kernel.org>
To: Nadeem Athani <nadeem@cadence.com>
Cc: Tom Joseph <tjoseph@cadence.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	PCI <linux-pci@vger.kernel.org>,
	devicetree@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	Milind Parab <mparab@cadence.com>,
	Swapnil Kashinath Jakhade <sjakhade@cadence.com>,
	Parshuram Raju Thombare <pthombar@cadence.com>
Subject: Re: [PATCH 1/2] dt-bindings:pci: Set LTSSM Detect.Quiet state delay.
Date: Tue, 9 Mar 2021 09:46:30 -0700	[thread overview]
Message-ID: <CAL_JsqJf1JHNEygoSPOqFocXL4F4M7p-MB-UxOp=D--NKnvTZw@mail.gmail.com> (raw)
In-Reply-To: <20210309073142.13219-2-nadeem@cadence.com>

On Tue, Mar 9, 2021 at 12:31 AM Nadeem Athani <nadeem@cadence.com> wrote:
>
> The parameter detect-quiet-min-delay can be used to program the minimum
> time that LTSSM waits on entering Detect.Quiet state.
> 00 : 0us minimum wait time in Detect.Quiet state.
> 01 : 100us minimum wait time in Detect.Quiet state.
> 10 : 1000us minimum wait time in Detect.Quiet state.
> 11 : 2000us minimum wait time in Detect.Quiet state.

What determines this setting? Is it per board or SoC? Is this a
standard PCI timing thing? Why does this need to be tuned per
platform?

> Signed-off-by: Nadeem Athani <nadeem@cadence.com>
> ---
>  .../devicetree/bindings/pci/cdns,cdns-pcie-host.yaml        | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> index 293b8ec318bc..a1d56e0be419 100644
> --- a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> +++ b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> @@ -27,6 +27,18 @@ properties:
>
>    msi-parent: true
>
> +  detect-quiet-min-delay:
> +    description:
> +      LTSSM Detect.Quiet state minimum delay.
> +      00 : 0us minimum wait time
> +      01 : 100us minimum wait time
> +      10 : 1000us minimum wait time
> +      11 : 2000us minimum wait time
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 0
> +    maximum: 3
> +    default: 0
> +
>  required:
>    - reg
>    - reg-names
> @@ -48,6 +60,7 @@ examples:
>              linux,pci-domain = <0>;
>              vendor-id = <0x17cd>;
>              device-id = <0x0200>;
> +            detect-quiet-min-delay = <0>;
>
>              reg = <0x0 0xfb000000  0x0 0x01000000>,
>                    <0x0 0x41000000  0x0 0x00001000>;
> --
> 2.15.0
>

  reply	other threads:[~2021-03-09 16:47 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-09  7:31 [PATCH 0/2] PCI: cadence: Set LTSSM Detect.Quiet state delay Nadeem Athani
2021-03-09  7:31 ` [PATCH 1/2] dt-bindings:pci: " Nadeem Athani
2021-03-09 16:46   ` Rob Herring [this message]
2021-03-14 18:56     ` Athani Nadeem Ladkhan
2021-03-09 17:19   ` Rob Herring
2021-03-09  7:31 ` [PATCH 2/2] PCI: cadence: " Nadeem Athani
2021-03-15 13:11   ` Kishon Vijay Abraham I

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