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Subject: Re: [PATCH v2 3/5] pcie-qcom: provide a way to power up qca6390 chip
 on RB5 platform
To:     Rob Herring <robh+dt@kernel.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Stanimir Varbanov <svarbanov@mm-sol.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        PCI <linux-pci@vger.kernel.org>
References: <20210128175225.3102958-1-dmitry.baryshkov@linaro.org>
 <20210128175225.3102958-4-dmitry.baryshkov@linaro.org>
 <CAL_JsqLRn40h0K-Fze5m1LS2+raLp94LariMkUh7XtekTBT5+Q@mail.gmail.com>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Message-ID: <da0ac373-4edb-0230-b264-49697fa3d86a@linaro.org>
Date:   Fri, 29 Jan 2021 06:45:21 +0300
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On 28/01/2021 22:26, Rob Herring 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.
> 
> 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?


> 
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index ab21aa01c95d..eb73c8540d4d 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -20,6 +20,7 @@
>>   #include <linux/of_device.h>
>>   #include <linux/of_gpio.h>
>>   #include <linux/pci.h>
>> +#include <linux/pm_domain.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/phy/phy.h>
>> @@ -1568,6 +1569,26 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0302, qcom_fixup_class);
>>   DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x1000, qcom_fixup_class);
>>   DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x1001, qcom_fixup_class);
>>
>> +static void qcom_fixup_power(struct pci_dev *dev)
>> +{
>> +       int ret;
>> +       struct pcie_port *pp = dev->bus->sysdata;
>> +       struct dw_pcie *pci;
>> +
>> +       if (!pci_is_root_bus(dev->bus))
>> +               return;
>> +
>> +       ret = dev_pm_domain_attach(&dev->dev, true);
>> +       if (ret < 0 || !dev->dev.pm_domain)
>> +               return;
>> +
>> +       pci = to_dw_pcie_from_pp(pp);
>> +       dev_info(&dev->dev, "Bus powered up, waiting for link to come up\n");
>> +
>> +       dw_pcie_wait_for_link(pci);
>> +}
>> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x010b, qcom_fixup_power);
>> +
>>   static struct platform_driver qcom_pcie_driver = {
>>          .probe = qcom_pcie_probe,
>>          .driver = {
>> --
>> 2.29.2
>>


-- 
With best wishes
Dmitry