Re: [BISECTED] (?) since 3.16: USB video cam of an HP Pavilion dv7 laptop not working

["Jörg-Volker Peetz" <jvpeetz@web.de>]

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Jörg-Volker Peetz wrote on 09/08/2014 17:17:
> Since 3.16 the builtin USB video cam of an HP Pavilion dv7 laptop shows only a
> black screen with the application guvcview although the video LED is turned on.
> There is no hint in dmesg. Also the output of guvcview shows no conspicuousness.
> 
> With kernel version 3.15.9 the camera works.
> 
> I tried to bisect between good v3.15 and bad v3.16, which identified
> 
> commit 9262c19d14c433a6a1ba25c3ff897cb89e412309
> Author: Dan Williams <dan.j.williams@intel.com>
> Date:   Tue May 20 18:08:12 2014 -0700
> 
>     usb: disable port power control if not supported in wHubCharacteristics
> 
>     A hub indicates whether it supports per-port power control via the
>     wHubCharacteristics field in its descriptor.  If it is not supported
>     a hub will still emulate ClearPortPower(PORT_POWER) requests by
>     stopping the link state machine.  However, since this does not save
>     power do not bother suspending.
> 
>     This also consolidates support checks into a
>     hub_is_port_power_switchable() helper.
> 
>     Acked-by: Alan Stern <stern@rowland.harvard.edu>
>     Signed-off-by: Dan Williams <dan.j.williams@intel.com>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> In the bad bisection steps the video device even was not found. Therefore, I'm
> not sure if I identified the right culprit.
> 

As you suggested Dan, I reverted this commit on top of 3.16.0 (the commit could
not be reverted cleanly, I had to do it manually, patch appended). But still I
see a black picture from the camera. So this commit is not the culprit.

How to proceed with the bisection?
-- 
Regards,
Jörg-Volker.


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--- hub.c.orig	2014-08-04 00:25:02.000000000 +0200
+++ hub.c	2014-09-09 11:56:24.721312469 +0200
@@ -820,6 +820,8 @@ EXPORT_SYMBOL_GPL(usb_hub_clear_tt_buffe
 static void hub_power_on(struct usb_hub *hub, bool do_delay)
 {
 	int port1;
+	u16 wHubCharacteristics =
+			le16_to_cpu(hub->descriptor->wHubCharacteristics);
 
 	/* Enable power on each port.  Some hubs have reserved values
 	 * of LPSM (> 2) in their descriptors, even though they are
@@ -827,7 +829,7 @@ static void hub_power_on(struct usb_hub
 	 * but only emulate it.  In all cases, the ports won't work
 	 * unless we send these messages to the hub.
 	 */
-	if (hub_is_port_power_switchable(hub))
+	if ((wHubCharacteristics & HUB_CHAR_LPSM) < 2)
 		dev_dbg(hub->intfdev, "enabling power on all ports\n");
 	else
 		dev_dbg(hub->intfdev, "trying to enable port power on "
@@ -4548,6 +4550,8 @@ static void hub_port_connect(struct usb_
 	unsigned unit_load;
 	struct usb_device *hdev = hub->hdev;
 	struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
+	unsigned wHubCharacteristics =
+			le16_to_cpu(hub->descriptor->wHubCharacteristics);
 	struct usb_port *port_dev = hub->ports[port1 - 1];
 	struct usb_device *udev = port_dev->child;
 
@@ -4586,7 +4590,7 @@ static void hub_port_connect(struct usb_
 			test_bit(port1, hub->removed_bits)) {
 
 		/* maybe switch power back on (e.g. root hub was reset) */
-		if (hub_is_port_power_switchable(hub)
+		if ((wHubCharacteristics & HUB_CHAR_LPSM) < 2
 				&& !port_is_power_on(hub, portstatus))
 			set_port_feature(hdev, port1, USB_PORT_FEAT_POWER);
 
--- hub.h.orig	2014-08-04 00:25:02.000000000 +0200
+++ hub.h	2014-09-09 12:52:40.027903791 +0200
@@ -119,16 +119,6 @@ extern int hub_port_debounce(struct usb_
 extern int usb_clear_port_feature(struct usb_device *hdev,
 		int port1, int feature);
 
-static inline bool hub_is_port_power_switchable(struct usb_hub *hub)
-{
-	__le16 hcs;
-
-	if (!hub)
-		return false;
-	hcs = hub->descriptor->wHubCharacteristics;
-	return (le16_to_cpu(hcs) & HUB_CHAR_LPSM) < HUB_CHAR_NO_LPSM;
-}
-
 static inline int hub_is_superspeed(struct usb_device *hdev)
 {
 	return hdev->descriptor.bDeviceProtocol == USB_HUB_PR_SS;
--- port.c.orig	2014-08-04 00:25:02.000000000 +0200
+++ port.c	2014-09-09 12:58:46.521229430 +0200
@@ -445,16 +445,11 @@ int usb_hub_create_port_device(struct us
 	 */
 	pm_runtime_set_active(&port_dev->dev);
 	pm_runtime_get_noresume(&port_dev->dev);
-	pm_runtime_enable(&port_dev->dev);
+	if (!dev_pm_qos_expose_flags(&port_dev->dev,
+			PM_QOS_FLAG_NO_POWER_OFF))
+		pm_runtime_enable(&port_dev->dev);
 	device_enable_async_suspend(&port_dev->dev);
 
-	/*
-	 * Keep hidden the ability to enable port-poweroff if the hub
-	 * does not support power switching.
-	 */
-	if (!hub_is_port_power_switchable(hub))
-		return 0;
-
 	/* Attempt to let userspace take over the policy. */
 	retval = dev_pm_qos_expose_flags(&port_dev->dev,
 			PM_QOS_FLAG_NO_POWER_OFF);