linux-kernel - Re: [PATCH v2 3/5] pcie-qcom: provide a way to power up qca6390 chip on RB5 platform

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Message-ID: <CAL_JsqJcBDfa6s7sG0Zho41T7zbVg15GH2WDh+inKNtTs+CcZw@mail.gmail.com>
Date:   Fri, 29 Jan 2021 17:39:18 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        PCI <linux-pci@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH v2 3/5] pcie-qcom: provide a way to power up qca6390 chip
 on RB5 platform

On Thu, Jan 28, 2021 at 9:45 PM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On 28/01/2021 22:26, Rob Herring wrote:
> > On Thu, Jan 28, 2021 at 11:52 AM Dmitry Baryshkov
> > <dmitry.baryshkov@...aro.org> wrote:
> >>
> >> Some Qualcomm platforms require to power up an external device before
> >> probing the PCI bus. E.g. on RB5 platform the QCA6390 WiFi/BT chip needs
> >> to be powered up before PCIe0 bus is probed. Add a quirk to the
> >> respective PCIe root bridge to attach to the power domain if one is
> >> required, so that the QCA chip is started before scanning the PCIe bus.
> >
> > This is solving a generic problem in a specific driver. It needs to be
> > solved for any PCI host and any device.
>
> Ack. I see your point here.
>
> As this would require porting code from powerpc/spark of-pci code and
> changing pcie port driver to apply power supply before bus probing
> happens, I'd also ask for the comments from PCI maintainers. Will that
> solution be acceptable to you?

Oh good, something exists. :)

FYI, there's another similar case needing this that just popped up[1].

Rob

[1] https://lore.kernel.org/linux-pci/20210129173057.30288c9d@coco.lan/