Date:   Wed, 6 Apr 2022 11:55:43 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
CC:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        "Sandeep Maheswaram (Temp)" <quic_c_sanm@...cinc.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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>,
        Peter Chen <peter.chen@...nel.org>,
        Pawel Laszczak <pawell@...ence.com>,
        Roger Quadros <rogerq@...nel.org>,
        Aswath Govindraju <a-govindraju@...com>,
        <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_ppratap@...cinc.com>,
        <quic_kriskura@...cinc.com>, <quic_pkondeti@...cinc.com>
Subject: Re: [PATCH v3 3/3] usb: dwc: host: add xhci_plat_priv quirk
 XHCI_SKIP_PHY_INIT

Hi Heikki/Mathias,

On Mon, Apr 04, 2022 at 01:55:16PM +0530, Pavan Kondeti wrote:
> Hi Heikki,
> 
> On Thu, Mar 31, 2022 at 02:16:53PM +0300, Heikki Krogerus wrote:
> > On Wed, Mar 30, 2022 at 08:47:34PM +0300, Mathias Nyman wrote:
> > > On 29.3.2022 12.18, Sandeep Maheswaram (Temp) wrote:
> > > > Hi Mathias,Heikki
> > > > 
> > > > On 3/25/2022 9:08 PM, Heikki Krogerus wrote:
> > > >> On Fri, Mar 25, 2022 at 04:33:27PM +0200, Mathias Nyman wrote:
> > > >>> On 25.3.2022 13.27, Heikki Krogerus wrote:
> > > >>>> On Fri, Mar 25, 2022 at 12:36:22AM +0200, Mathias Nyman wrote:
> > > >>>>> On 24.3.2022 14.27, Heikki Krogerus wrote:
> > > >>>>>> On Thu, Mar 24, 2022 at 12:07:11PM +0530, Sandeep Maheswaram wrote:
> > > >>>>>>> Currently the phy init is done from dwc3 and also xhci which makes the
> > > >>>>>>> runtime_usage value 2 for the phy which causes issue during runtime
> > > >>>>>>> suspend. When we run the below command the runtime_status still shows
> > > >>>>>>> active.
> > > >>>>>>> echo auto > /sys/bus/platform/devices/88e3000.phy/power/control
> > > >>>>>>>
> > > >>>>>>> dwc3 manages PHY by own DRD driver, so skip the management by
> > > >>>>>>> HCD core by setting this quirk.
> > > >>>>>>>
> > > >>>>>>> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@...cinc.com>
> > > >>>>>>> ---
> > > >>>>>>>   drivers/usb/dwc3/host.c | 13 +++++++++++++
> > > >>>>>>>   1 file changed, 13 insertions(+)
> > > >>>>>>>
> > > >>>>>>> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
> > > >>>>>>> index eda8719..d4fcf06 100644
> > > >>>>>>> --- a/drivers/usb/dwc3/host.c
> > > >>>>>>> +++ b/drivers/usb/dwc3/host.c
> > > >>>>>>> @@ -13,6 +13,12 @@
> > > >>>>>>>   #include <linux/platform_device.h>
> > > >>>>>>>     #include "core.h"
> > > >>>>>>> +#include <linux/usb/xhci-plat.h>
> > > >>>>>>> +#include <linux/usb/xhci-quirks.h>
> > > >>>>>>> +
> > > >>>>>>> +static const struct xhci_plat_priv xhci_plat_dwc3_xhci = {
> > > >>>>>>> +    .quirks = XHCI_SKIP_PHY_INIT,
> > > >>>>>>> +};
> > > >>>>>>>     static void dwc3_host_fill_xhci_irq_res(struct dwc3 *dwc,
> > > >>>>>>>                       int irq, char *name)
> > > >>>>>>> @@ -122,6 +128,13 @@ int dwc3_host_init(struct dwc3 *dwc)
> > > >>>>>>>           }
> > > >>>>>>>       }
> > > >>>>>>>   +    ret = platform_device_add_data(xhci, &xhci_plat_dwc3_xhci,
> > > >>>>>>> +            sizeof(xhci_plat_dwc3_xhci));
> > > >>>>>>> +    if (ret) {
> > > >>>>>>> +        dev_err(dwc->dev, "failed to add data to xHCI\n");
> > > >>>>>>> +        goto err;
> > > >>>>>>> +    }
> > > >>>>>>> +
> > > >>>>>>>       ret = platform_device_add(xhci);
> > > >>>>>>>       if (ret) {
> > > >>>>>>>           dev_err(dwc->dev, "failed to register xHCI device\n");
> > > >>>>>> I think you should just use device property:
> > > >>>>>>
> > > >>>>> This was suggested in an earlier series, but was rejected as it also added
> > > >>>>> the property as a device tree parameter.
> > > >>>>>
> > > >>>>> I think adding more device properties can be messy in the long run, especially if we
> > > >>>>> need to add them for many of the existing xhci quirks.
> > > >>>>> We also end up with a mix where some device properties are listed as device tree
> > > >>>>> parameters, and some not.
> > > >>>>>
> > > >>>>> Defining xhci quirks and platform data structure in headers shared with dwc3 and cdns3
> > > >>>>> allow those drivers to easily set any existing xhci quirk, or other possible optional
> > > >>>>> callbacks.
> > > >>>>>
> > > >>>>> cdns3 driver is already doing this, but it includes the full xhci.h header.
> > > >>>>> This series cleans up that a bit so cdns3 will only include xhci quirk bits and
> > > >>>>> platform data structure.
> > > >>>>>
> > > >>>>> On the downside we add a couple xhci related header files to include/linux/usb/
> > > >>>>> Let me know if you see any other issues I missed with this approach.
> > > >>>> The problem here is that these drivers are now coupled together, and
> > > >>>> that should not be taken lightly. We have a dependency hell in our
> > > >>>> hands with a lot of drivers, and the culprit is always platform data.
> > > >>>>
> > > >>>> Build-in device properties may be messy, but I would still say they
> > > >>>> are less messy than those quirk flags - you got to admit, they are a
> > > >>>> mess. The benefit from build-in properties is in any case the fact
> > > >>>> that they remove the need to couple these drivers together.
> > > >>> Agree, quirk bits are messy. Any suggestion that would work with
> > > >>> PCI xHCI devices, devicetree, and "pure" platform devices?
> > > >> I think xHCI driver should always be able to rely on being able to
> > > >> read this kind of information from the fwnode. If there is no actual
> > > >> firmware node (DT or ACPI), or if it's missing some information, the
> > > >> glue driver needs to populate software node for the xHCI.
> > > >>
> > > >> Right now I just want to avoid having to pass the quirks using
> > > >> platform data from drivers such as drivers/usb/cdns3/host.c and
> > > >> drivers/usb/dwc3/host.c to xHCI.
> > > >>
> > > >> One way we could do that is by defining compatibility ID for both of
> > > >> them that we provide using a single device property (like I guess DT
> > > >> does). Then based on that compatibility ID, xhci-plat.c can set the
> > > >> actual "static" quirk flags. That we could already do easily. How
> > > >> would that sound to you?
> > > 
> > > Sounds good. 
> > > 
> > > > 
> > > > This was my previous patch where I was using device tree property. Should we go ahead with this approach?
> > > > 
> > > > https://patchwork.kernel.org/project/linux-arm-msm/cover/1636353710-25582-1-git-send-email-quic_c_sanm@quicinc.com/
> > > > 
> > > > Any further changes to this ?
> > > 
> > > By dropping the DT part of that series we get a similar built-in device property
> > > solution as Heikki initially suggested.
> > > 
> > > How about adding the compatibility ID device property that was just suggested?
> > > Then matching the Id in xhci-plat.c against a static table containing Ids and
> > > xhci_plat_priv structures, with the needed quirks for dwc3.
> > 
> > There was a comment from Pavan. Is it still possible to get this
> > detail from DT?
> > I guess that would still be ideal, right?
> > 
> I was suggesting if we can have device tree param like the patch sandeep
> pointed out.
> 
> How would adding a compatible index to usb_xhci_of_match[] would work
> actually? I ask this because, dwc3/host.c creates platform device and
> it is not associated with any of_node, so of_driver_match_device() called
> from platform bus match method does not work. one way to achieve this would
> be by matching against sysdev. Something like below. Is it acceptible?
> 
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 649ffd8..bd5d055 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -126,6 +126,10 @@ static const struct xhci_plat_priv xhci_plat_brcm = {
>  	.quirks = XHCI_RESET_ON_RESUME,
>  };
>  
> +static const struct xhci_plat_priv xhci_plat_dwc3 = {
> +	.quirks = XHCI_SKIP_PHY_INIT,
> +};
> +
>  static const struct of_device_id usb_xhci_of_match[] = {
>  	{
>  		.compatible = "generic-xhci",
> @@ -167,6 +171,9 @@ static const struct of_device_id usb_xhci_of_match[] = {
>  	}, {
>  		.compatible = "brcm,bcm7445-xhci",
>  		.data = &xhci_plat_brcm,
> +	}, {
> +		.compatible = "snps,dwc3",
> +		.data = &xhci_plat_dwc3,
>  	},
>  	{},
>  };
> @@ -274,6 +281,15 @@ static int xhci_plat_probe(struct platform_device *pdev)
>  	else
>  		priv_match = dev_get_platdata(&pdev->dev);
>  
> +	/* allow private data mapping with the sysdev compatible */
> +	if (!priv_match) {
> +		struct of_device_id *match;
> +
> +		match = of_match_device(usb_xhci_of_match, sysdev);
> +		if (match)
> +			priv_match = match->data;
> +	}
> +
>  	if (priv_match) {
>  		priv = hcd_to_xhci_priv(hcd);
>  		/* Just copy data for now */
> 
> > I have another question. Can't we now just assume that if the sysdev
> > is the parent (or grandparent), then the phy initialization should
> > always be skipped? In that case we could just do something like this:
> > 
> > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > index 649ffd861b44e..1018b33488046 100644
> > --- a/drivers/usb/host/xhci-plat.c
> > +++ b/drivers/usb/host/xhci-plat.c
> > @@ -212,8 +212,12 @@ static int xhci_plat_probe(struct platform_device *pdev)
> >  #endif
> >         }
> >  
> > -       if (!sysdev)
> > +       if (sysdev) {
> > +               if (sysdev != &pdev->dev)
> > +                       hcd->skip_phy_initialization = 1;
> > +       } else {
> >                 sysdev = &pdev->dev;
> > +       }
> >  
> >         if (WARN_ON(!sysdev->dma_mask))
> >                 /* Platform did not initialize dma_mask */
> > 
> > 
> > I did not go through all the drivers that carefully, so I may have
> > missed something, but it looks like the only drivers that can have the
> > sysdev as the parent or grandparent are cdns3 and dwc3.
> > 
> I cross checked and these are two drivers that are creating xhci-plat device.
> So this patch would definitely work. However I am not sure in future if any
> device created via device tree would want to use this feature. For now,
> it looks good. It Mathias, Do you see any problem with this approach?
> 

Can you please provide your suggestions on this? We have discussed about
3 approaches here other than the whole platform data refactoring done.

(1) Introduce a new dT property and expect dwc3/host.c to set this property
to skip the phy initialization.
(2) Allow platform private data match based on the sysdev. The diff I sent
in the previous email.
(3) Heikki's suggestion of relying on the fact that the users of phy skip
init can be tested with sysdev != &pdev->dev check.

Thanks,
Pavan

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