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

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Date:   Sat, 30 Jan 2021 19:12:25 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Yassine Oudjana <y.oudjana@...tonmail.com>
Cc:     "agross@...nel.org" <agross@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "manivannan.sadhasivam@...aro.org" <manivannan.sadhasivam@...aro.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "svarbanov@...sol.com" <svarbanov@...sol.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH v2 3/5] pcie-qcom: provide a way to power up qca6390 chip
 on RB5 platform

On Sat, 30 Jan 2021 at 11:04, Yassine Oudjana <y.oudjana@...tonmail.com> 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.
>
> I'm lead to believe that this is also needed for QCA6174. I tried taking
> the driver you wrote and changing regulators to match the ones used by QCA6174,
> but I found that it gets probed after PCIe, which makes it get -EPROBE_DEFER
> when it tries to attach to the power domain, which it doesn't handle it and
> just proceeds to scan the bus and not find the chip as usual.

As a quick hack, you can try using this power domain for the pci_phy
(see my v1). Rob declined this approach, but it is useful to check if
QCA6174 wakes up properly and deferring PCIe probing till the chip is
powered up.



-- 
With best wishes
Dmitry