linux-kernel - Re: [PATCH v5] usb: host: xhci-plat: Set XHCI_SKIP_PHY

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Date:   Wed, 9 Feb 2022 11:31:06 +0530
From:   Sandeep Maheswaram <quic_c_sanm@...cinc.com>
To:     Pavan Kondeti <quic_pkondeti@...cinc.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Felipe Balbi <balbi@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        "Doug Anderson" <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_ppratap@...cinc.com>
Subject: Re: [PATCH v5] usb: host: xhci-plat: Set XHCI_SKIP_PHY_INIT quirk for
 DWC3 controller


On 2/9/2022 11:23 AM, Pavan Kondeti wrote:
> On Tue, Feb 08, 2022 at 11:11:53AM +0100, Greg Kroah-Hartman wrote:
>> On Tue, Feb 08, 2022 at 03:34:22PM +0530, Sandeep Maheswaram wrote:
>>> Hi Greg,
>>>
>>> On 1/27/2022 10:28 AM, Sandeep Maheswaram wrote:
>>>> On 1/26/2022 5:55 PM, Greg Kroah-Hartman wrote:
>>>>> On Fri, Jan 07, 2022 at 10:27:59AM +0530, Sandeep Maheswaram wrote:
>>>>>> On 1/6/2022 7:55 PM, Greg Kroah-Hartman wrote:
>>>>>>> On Wed, Dec 22, 2021 at 11:39:43AM +0530, Sandeep Maheswaram wrote:
>>>>>>>> Set XHCI_SKIP_PHY_INIT quirk to avoid phy initialization twice.
>>>>>>>> Runtime suspend of phy drivers was failing from DWC3
>>>>>>>> driver as runtime
>>>>>>>> usage value is 2 because the phy is initialized from
>>>>>>>> DWC3 and HCD core.
>>>>>>>> DWC3 manages phy in their core drivers. Set this quirk to avoid phy
>>>>>>>> initialization in HCD core.
>>>>>>>>
>>>>>>>> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
>>>>>>>> ---
>>>>>>>> v5:
>>>>>>>> Added comment to explain the change done.
>>>>>>>> v4:
>>>>>>>> Changed pdev->dev.parent->of_node to sysdev->of_node
>>>>>>>>
>>>>>>>>     drivers/usb/host/xhci-plat.c | 8 ++++++++
>>>>>>>>     1 file changed, 8 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/usb/host/xhci-plat.c
>>>>>>>> b/drivers/usb/host/xhci-plat.c
>>>>>>>> index c1edcc9..e6014d4 100644
>>>>>>>> --- a/drivers/usb/host/xhci-plat.c
>>>>>>>> +++ b/drivers/usb/host/xhci-plat.c
>>>>>>>> @@ -327,6 +327,14 @@ static int xhci_plat_probe(struct
>>>>>>>> platform_device *pdev)
>>>>>>>>                          &xhci->imod_interval);
>>>>>>>>         }
>>>>>>>> +    /*
>>>>>>>> +     * Set XHCI_SKIP_PHY_INIT quirk to avoid phy
>>>>>>>> initialization twice.
>>>>>>>> +     * DWC3 manages phy in their core drivers. Set this
>>>>>>>> quirk to avoid phy
>>>>>>>> +     * initialization in HCD core.
>>>>>>>> +     */
>>>>>>>> +    if (of_device_is_compatible(sysdev->of_node, "snps,dwc3"))
>>>>>>>> +        xhci->quirks |= XHCI_SKIP_PHY_INIT;
>>>>>>>> +
>>>>>>> Why is this function caring about dwc3 stuff?  Shoudn't this be a
>>>>>>> "generic" device property instead of this device-specific one?
>>>>>>>
>>>>>>> thanks,
>>>>>>>
>>>>>>> greg k-h
>>>>>> This quirk is set only if required for some controllers (eg:
>>>>>> dwc3 & cdns3).
>>>>>>
>>>>>> Please check below commit.
>>>>>>
>>>>>> https://lore.kernel.org/all/20200918131752.16488-5-mathias.nyman@linux.intel.com/
>>>>>>
>>>>> That commit has nothing to do with a specific "dwc3" quirk anywhere.
>>>>> Why not set this flag in the specific platform xhci driver instead where
>>>>> it belongs?
>>>>>
>>>>> thanks,
>>>>>
>>>>> greg k-h
>>>> There is no specific xhci platform driver for dwc3 controllers.
>>>>
>>>> dwc3 controllers use xhci-plat driver .
>>>>
>>>> We can add this quirk in usb/dwc3/host.c as cdns3 does but that requires
>>>> tying dwc3 and xhci driver .
>>>>
>>>> https://patchwork.kernel.org/project/linux-arm-msm/patch/1633946518-13906-1-git-send-email-sanm@codeaurora.org/
>>>>
>>>>
>>>> Regards
>>>>
>>>> Sandeep
>>>>
>>>>
>>> Can you suggest any other method to set this quirk for dwc3 controllers.
>> No idea, sorry.
> Sandeep,
>
> I agree with Greg's comments here. The compatible based check to detect dwc3
> controller is not elegant. Your proposal of adding a device tree param is
> overkill, I believe.
>
> Greg already gave us a pointer here [1] which I feel is the best approach going
> forward. We know that xhci-plat is being used by drivers like dwc3, cdns3 and
> these drivers need to expose their xhci quirks. As Greg suggested, why can't
> we move xhci quirks definition to include/linux/usb/xhci-quriks.h and directly
> access from the glue drivers? The attached is the patch (completely untested)
> for your reference. It will prepare the setup for you to add the private data
> and quirks in the dwc3 host glue driver.
>
> Thanks,
> Pavan
>
> [1]
> https://patchwork.kernel.org/project/linux-arm-msm/patch/1633946518-13906-1-git-send-email-sanm@codeaurora.org/
>
Thanks Pavan..will test the patch.