linux-kernel - Re: [PATCH 2/5] PCI: dwc: Add support for retaining link during host init

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Message-ID: <816456c5-ad32-4829-ae0d-a0d09f468863@oss.qualcomm.com>
Date: Mon, 12 Jan 2026 12:29:26 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Bjorn Helgaas <helgaas@...nel.org>,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>, Neil Armstrong
 <neil.armstrong@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jingoo Han <jingoohan1@...il.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 2/5] PCI: dwc: Add support for retaining link during host
 init

On 1/9/26 4:53 PM, Bjorn Helgaas wrote:
> On Fri, Jan 09, 2026 at 12:51:07PM +0530, Krishna Chaitanya Chundru wrote:
>> Some platforms keep the PCIe link up across bootloader and kernel
>> handoff. In such cases, reinitializing the root complex is unnecessary
>> if the DWC glue drivers wants to retain the PCIe link.
>>
>> Introduce a link_retain flag in struct dw_pcie_rp to indicate that
>> the link should be preserved. When this flag is set by DWC glue drivers,
>> skip dw_pcie_setup_rc() and only initialize MSI, avoiding redundant
>> configuration steps.
> 
> It sounds like this adds an assumption that the bootloader
> initialization is the same as what dw_pcie_setup_rc() would do.  This
> assumption also applies to future changes in dw_pcie_setup_rc().
> 
> It looks like you mention an issue like this in [PATCH 4/5]; DBI & ATU
> base being different than "HLOS" (whatever that is).  This sounds like

FYI, "HLOS" is a Qualcomm term for "High-Level OS".. which is a very
pedantic way to say "OS"

Konrad