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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Sat, 30 Jan 2021 19:12:25 +0300
Message-ID: <CAA8EJpqeMgfWz2XJKxTb=9AuShVtwHGp0xjGmcESBf5CNUv4CA@mail.gmail.com>
Subject: Re: [PATCH v2 3/5] pcie-qcom: provide a way to power up qca6390 chip
 on RB5 platform
To:     Yassine Oudjana <y.oudjana@protonmail.com>
Cc:     "agross@kernel.org" <agross@kernel.org>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "arnd@arndb.de" <arnd@arndb.de>,
        "bjorn.andersson@linaro.org" <bjorn.andersson@linaro.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
        "manivannan.sadhasivam@linaro.org" <manivannan.sadhasivam@linaro.org>,
        "mchehab@kernel.org" <mchehab@kernel.org>,
        "svarbanov@mm-sol.com" <svarbanov@mm-sol.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>
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On Sat, 30 Jan 2021 at 11:04, Yassine Oudjana <y.oudjana@protonmail.com> wrote:
>
> On Thu, Jan 28, 2021 at 11:52 AM Dmitry Baryshkov
> <dmitry.baryshkov@linaro.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