linux-kernel - [RFC PATCH] usb: dwc3: enable runtime PM for drd role switch / extcon

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Message-Id: <20200312143038.11719-1-martin.kepplinger@puri.sm>
Date:   Thu, 12 Mar 2020 15:30:38 +0100
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     balbi@...nel.org, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Martin Kepplinger <martin.kepplinger@...i.sm>
Subject: [RFC PATCH] usb: dwc3: enable runtime PM for drd role switch / extcon

Note: runtime PM currently needs to be enabled ("auto") manually via sysfs as
its power/control is set to "on" by the driver.

When runtime PM enabled, dwc3 currently doesn't resume when a cable is connected.
It only suspends after a cable is disconnected.

When using an extcon driver (for a different chip on the board), dwc3 can
register a hook for that. (Still undocumented -> TODO?).

Make sure, dwc3 is resumed when "set_mode" is being called by drd.

this is only a question about what's missing to properly keep runtime
PM enabled for dwc3 and if my change makes any sense at all. It seems
to work fine for me...

I'm glad about any hints on how to keep runtime PM enabled (at least when
having an extcon hook set up).

thanks,
                                martin
---
 drivers/usb/dwc3/core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 1d85c42b9c67..201b712bd961 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -118,6 +118,9 @@ static void __dwc3_set_mode(struct work_struct *work)
 	unsigned long flags;
 	int ret;

+	pm_runtime_mark_last_busy(dwc->dev);
+	pm_runtime_put_sync_autosuspend(dwc->dev);
+
 	if (dwc->dr_mode != USB_DR_MODE_OTG)
 		return;

@@ -196,6 +199,8 @@ void dwc3_set_mode(struct dwc3 *dwc, u32 mode)
 {
 	unsigned long flags;

+	pm_runtime_get_sync(dwc->dev);
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	dwc->desired_dr_role = mode;
 	spin_unlock_irqrestore(&dwc->lock, flags);
@@ -1552,7 +1557,7 @@ static int dwc3_probe(struct platform_device *pdev)
 		goto err5;

 	dwc3_debugfs_init(dwc);
-	pm_runtime_put(dev);
+	pm_runtime_put_sync(dev);

 	return 0;

-- 
2.20.1