Re: [PATCH v9 1/5] usb: host: xhci: plat: Add suspend quirk for dwc3 controller

[Matthias Kaehlcke <mka@chromium.org>]

Hi Sandeep,

On Mon, Nov 01, 2021 at 01:23:40PM +0530, Sandeep Maheswaram wrote:
> During suspend check if any wakeup capable devices are connected to the
> controller (directly or through hubs), and set the wakeup capable property
> for xhci plat device.
> 
> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@quicinc.com>
> ---
>  drivers/usb/host/xhci-plat.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index c1edcc9..7ab272b 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -431,6 +431,14 @@ static int xhci_plat_remove(struct platform_device *dev)
>  	return 0;
>  }
>  
> +static void xhci_dwc3_suspend_quirk(struct usb_hcd *hcd, struct device *dev)
> +{
> +	if (usb_wakeup_enabled_descendants(hcd->self.root_hub))
> +		device_set_wakeup_capable(dev, true);
> +	else
> +		device_set_wakeup_capable(dev, false);

IIUC wakeup capability is typically a static property that reflects the
actual hardware (or firmware) support for wakeup. In that sense it doesn't
seem a good idea to change it dynamically at suspend time, depending on
what is connected to the bus. I understand though that the odd split
of the dwc3 driver makes it hard to do things properly ...

Earlier in this discussion Felipe suggested to add a function like
device_children_wakeup_capable(), to avoid having to call
usb_wakeup_enabled_descendants() from the dwc3 drivers.

Below is an initial implementation for device_children_wakeup_capable(),
could you try if calling it from dwc3_suspend/resume_common() and
dwc3_qcom_suspend() would work instead of relying on the wakeup
capability?

Thanks

Matthias

From 97c838334045ed67c3943f8e035ac70acd12b89b Mon Sep 17 00:00:00 2001
From: Matthias Kaehlcke <mka@chromium.org>
Date: Mon, 1 Nov 2021 11:37:19 -0700
Subject: [PATCH] PM / wakeup: Add device_children_wakeup_capable()

Add device_children_wakeup_capable() which checks whether the device itself
or one if its descendants is wakeup capable.

Change-Id: Ib359eb5ac8650ddf9889c7d1f77707f50777fe99
Suggested-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
 drivers/base/power/wakeup.c | 17 +++++++++++++++++
 include/linux/pm_wakeup.h   |  6 ++++++
 2 files changed, 23 insertions(+)

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 9c0932603642..2aee7fa8230f 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -483,6 +483,23 @@ int device_set_wakeup_enable(struct device *dev, bool enable)
 }
 EXPORT_SYMBOL_GPL(device_set_wakeup_enable);
 
+static int __device_children_wakeup_capable(struct device *dev, void *dummy)
+{
+	return device_may_wakeup(dev) ||
+		device_for_each_child(dev, NULL, __device_children_wakeup_capable);
+}
+
+/**
+ * device_children_wakeup_capable - Check whether a device or one of its descendants is
+ *                                  wakeup capable.
+ * @dev: Device to handle.
+ */
+bool device_children_wakeup_capable(struct device *dev)
+{
+	return __device_children_wakeup_capable(dev, NULL);
+}
+EXPORT_SYMBOL_GPL(device_children_wakeup_capable);
+
 /**
  * wakeup_source_not_registered - validate the given wakeup source.
  * @ws: Wakeup source to be validated.
diff --git a/include/linux/pm_wakeup.h b/include/linux/pm_wakeup.h
index 661efa029c96..a0ca42aac6d6 100644
--- a/include/linux/pm_wakeup.h
+++ b/include/linux/pm_wakeup.h
@@ -97,6 +97,7 @@ extern int device_wakeup_disable(struct device *dev);
 extern void device_set_wakeup_capable(struct device *dev, bool capable);
 extern int device_init_wakeup(struct device *dev, bool val);
 extern int device_set_wakeup_enable(struct device *dev, bool enable);
+extern bool device_children_wakeup_capable(struct device *dev);
 extern void __pm_stay_awake(struct wakeup_source *ws);
 extern void pm_stay_awake(struct device *dev);
 extern void __pm_relax(struct wakeup_source *ws);
@@ -167,6 +168,11 @@ static inline bool device_may_wakeup(struct device *dev)
 
 static inline void device_set_wakeup_path(struct device *dev) {}
 
+static inline bool device_children_wakeup_capable(struct device *dev)
+{
+	return false;
+}
+
 static inline void __pm_stay_awake(struct wakeup_source *ws) {}
 
 static inline void pm_stay_awake(struct device *dev) {}