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

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Date:   Tue, 8 Feb 2022 15:34:22 +0530
From:   Sandeep Maheswaram <quic_c_sanm@...cinc.com>
To:     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_pkondeti@...cinc.com>,
        <quic_ppratap@...cinc.com>
Subject: Re: [PATCH v5] usb: host: xhci-plat: Set XHCI_SKIP_PHY_INIT quirk for
 DWC3 controller

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.

Regards

Sandeep