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

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Date:   Thu, 27 Jan 2022 10:28:52 +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


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