linux-kernel - Re: [PATCH v3] PCI: Add D3 support for PCI bridges in DT based platforms

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Message-ID: <20240214121946.GA6838@wunner.de>
Date: Wed, 14 Feb 2024 13:19:46 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczy??ski <kw@...ux.com>, Rob Herring <robh@...nel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	quic_krichai@...cinc.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3] PCI: Add D3 support for PCI bridges in DT based
 platforms

On Wed, Feb 14, 2024 at 05:16:09PM +0530, Manivannan Sadhasivam wrote:
> Currently, PCI core will enable D3 support for PCI bridges only when the
> following conditions are met:
> 
> 1. Platform is ACPI based
> 2. Thunderbolt controller is used
> 3. pcie_port_pm=force passed in cmdline
> 
> While options 1 and 2 do not apply to most of the DT based platforms,
> option 3 will make the life harder for distro maintainers. Due to this,
> runtime PM is also not getting enabled for the bridges.
> 
> To fix this, let's make use of the "supports-d3" property [1] in the bridge
> DT nodes to enable D3 support for the capable bridges. This will also allow
> the capable bridges to support runtime PM, thereby conserving power.
[...]
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Reviewed-by: Lukas Wunner <lukas@...ner.de>