Date:   Tue, 29 Mar 2022 14:58:59 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     "Sandeep Maheswaram (Temp)" <quic_c_sanm@...cinc.com>
CC:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.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_pkondeti@...cinc.com>,
        <quic_ppratap@...cinc.com>
Subject: Re: [PATCH v3 3/3] usb: dwc: host: add xhci_plat_priv quirk
 XHCI_SKIP_PHY_INIT

On Tue, Mar 29, 2022 at 02:48:05PM +0530, 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?
> 
> 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 ?
> 

Actually the dT idea looks better than the platform data. Earlier, we decided
to use if (of_device_is_compatible(dev->parent->of_node, "snps,dwc3")) check
but I feel that we should just introduce a device tree param that specify
this functionality (skipping phy init). we don't want xhci-plat to know that
this is dwc3/xyz device. we expect it to be abstracted.

Thanks,
Pavan

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