Date:   Wed, 6 Apr 2022 16:31:53 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
CC:     Pavan Kondeti <quic_pkondeti@...cinc.com>,
        Heikki Krogerus <heikki.krogerus@...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>
Subject: Re: [PATCH v3 3/3] usb: dwc: host: add xhci_plat_priv quirk
 XHCI_SKIP_PHY_INIT

Hi Mathias,

On Wed, Apr 06, 2022 at 01:52:56PM +0300, Mathias Nyman wrote:
> Hi
> 
> Sorry about the delayed response.
> 
> 
> On 6.4.2022 9.25, Pavan Kondeti wrote:
> > 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,
> >>  	},
> 
> Isn't there a risk that xhci-plat now binds to the parent dwc3 device?
> competing with the similar of_match_table entry created in drivers/usb/dwc3/core.c

Sill of me. Yes, it does not work. Thanks for pointing it out.

> 
> >>  	{},
> >>  };
> >> @@ -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?
> >>
> 
> Would work for now but seems like a risk to assume this would hold for all future
> xhci platform devices. 
> 
Agree that it may break in future for other drivers.

> > 
> > 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.
> 
> Adding one more device property to swnode in dwc3/host.c starts
> to look like the best option for now even if it didn't appeal initially.
> 
> The place creating the xhci platform device should have best info on what properties
> are needed for the platform device.
> 
> So this would be just like Heikki's first suggestion, or Sandeep's patches 2/3 and 3/3 in:
> https://patchwork.kernel.org/project/linux-arm-msm/cover/1636353710-25582-1-git-send-email-quic_c_sanm@quicinc.com/
> but without the devicetree binding documentation part.
> 
Why do you say devicetree binding doc is not needed in this case? Possible
that xhci-plat's device can be coming from dT and this param is passed to
skip initialization of PHY.

Thanks,
Pavan

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