[PATCH] usb: hub: port: add sysfs entry to switch port power

[PATCH] usb: hub: port: add sysfs entry to switch port power

[Michael Grzeschik]

This patch adds an sysfs switch to enable/disable a port on an power
switchable hub. It also ensures that the associated device gets
disconnected from the logical usb tree.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
---
 drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index d5bc36ca5b1f77..abc618d87888f3 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -17,6 +17,52 @@ static int usb_port_block_power_off;
 
 static const struct attribute_group *port_dev_group[];
 
+static ssize_t port_power_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct usb_port *port_dev = to_usb_port(dev);
+	struct usb_device *udev = port_dev->child;
+	struct usb_device *hdev = to_usb_device(dev->parent->parent);
+	struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
+	int port1 = port_dev->portnum;
+	bool value;
+	int rc = 0;
+
+	if (!hub)
+		return -EINVAL;
+
+	if (hub->in_reset)
+		return -EBUSY;
+
+	rc = strtobool(buf, &value);
+	if (rc)
+		return rc;
+
+	if (value)
+		usb_remote_wakeup(hdev);
+
+	rc = usb_hub_set_port_power(hdev, hub, port1, value);
+	if (rc)
+		return rc;
+
+	if (!value) {
+		usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
+		if (!port_dev->is_superspeed)
+			usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);
+
+		if (udev) {
+			port_dev->child = NULL;
+			usb_disconnect(&udev);
+		}
+	}
+
+	if (!rc)
+		rc = count;
+
+	return rc;
+}
+static DEVICE_ATTR_WO(port_power);
+
 static ssize_t location_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
@@ -153,6 +199,7 @@ static struct attribute *port_dev_attrs[] = {
 	&dev_attr_location.attr,
 	&dev_attr_quirks.attr,
 	&dev_attr_over_current_count.attr,
+	&dev_attr_port_power.attr,
 	NULL,
 };
 
-- 
2.30.2

Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Greg KH]

On Wed, May 11, 2022 at 01:13:17AM +0200, Michael Grzeschik wrote:
> This patch adds an sysfs switch to enable/disable a port on an power
> switchable hub. It also ensures that the associated device gets
> disconnected from the logical usb tree.
> 
> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> ---
>  drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)

No Documentation/ABI/ update as well?  That means I can't take this
change or even properly review it :(

Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Michael Grzeschik]

[-- Attachment #1: Type: text/plain, Size: 981 bytes --]

On Wed, May 11, 2022 at 07:43:22AM +0200, Greg KH wrote:
>On Wed, May 11, 2022 at 01:13:17AM +0200, Michael Grzeschik wrote:
>> This patch adds an sysfs switch to enable/disable a port on an power
>> switchable hub. It also ensures that the associated device gets
>> disconnected from the logical usb tree.
>>
>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>> ---
>>  drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 47 insertions(+)
>
>No Documentation/ABI/ update as well?  That means I can't take this
>change or even properly review it :(

I knew that I missed something. Will add it in v2.

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[kernel test robot]

Hi Michael,

I love your patch! Yet something to improve:

[auto build test ERROR on usb/usb-testing]
[also build test ERROR on v5.18-rc6 next-20220510]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Michael-Grzeschik/usb-hub-port-add-sysfs-entry-to-switch-port-power/20220511-071411
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
config: arc-vdk_hs38_smp_defconfig (https://download.01.org/0day-ci/archive/20220511/202205111601.PmB3PwmE-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 11.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/19efde40be7597697c54241a120f812d5864b677
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Michael-Grzeschik/usb-hub-port-add-sysfs-entry-to-switch-port-power/20220511-071411
        git checkout 19efde40be7597697c54241a120f812d5864b677
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash drivers/usb/core/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/usb/core/port.c: In function 'port_power_store':
>> drivers/usb/core/port.c:42:17: error: implicit declaration of function 'usb_remote_wakeup' [-Werror=implicit-function-declaration]
      42 |                 usb_remote_wakeup(hdev);
         |                 ^~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/usb_remote_wakeup +42 drivers/usb/core/port.c

    19	
    20	static ssize_t port_power_store(struct device *dev, struct device_attribute *attr,
    21				    const char *buf, size_t count)
    22	{
    23		struct usb_port *port_dev = to_usb_port(dev);
    24		struct usb_device *udev = port_dev->child;
    25		struct usb_device *hdev = to_usb_device(dev->parent->parent);
    26		struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
    27		int port1 = port_dev->portnum;
    28		bool value;
    29		int rc = 0;
    30	
    31		if (!hub)
    32			return -EINVAL;
    33	
    34		if (hub->in_reset)
    35			return -EBUSY;
    36	
    37		rc = strtobool(buf, &value);
    38		if (rc)
    39			return rc;
    40	
    41		if (value)
  > 42			usb_remote_wakeup(hdev);
    43	
    44		rc = usb_hub_set_port_power(hdev, hub, port1, value);
    45		if (rc)
    46			return rc;
    47	
    48		if (!value) {
    49			usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
    50			if (!port_dev->is_superspeed)
    51				usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);
    52	
    53			if (udev) {
    54				port_dev->child = NULL;
    55				usb_disconnect(&udev);
    56			}
    57		}
    58	
    59		if (!rc)
    60			rc = count;
    61	
    62		return rc;
    63	}
    64	static DEVICE_ATTR_WO(port_power);
    65	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Alan Stern]

On Wed, May 11, 2022 at 01:13:17AM +0200, Michael Grzeschik wrote:
> This patch adds an sysfs switch to enable/disable a port on an power
> switchable hub. It also ensures that the associated device gets
> disconnected from the logical usb tree.

This says what the patch does.  It does not explain why the patch was 
written or why anybody would want to switch the power on a hub's port.

> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> ---
>  drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index d5bc36ca5b1f77..abc618d87888f3 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -17,6 +17,52 @@ static int usb_port_block_power_off;
>  
>  static const struct attribute_group *port_dev_group[];
>  
> +static ssize_t port_power_store(struct device *dev, struct device_attribute *attr,
> +			    const char *buf, size_t count)
> +{
> +	struct usb_port *port_dev = to_usb_port(dev);
> +	struct usb_device *udev = port_dev->child;
> +	struct usb_device *hdev = to_usb_device(dev->parent->parent);
> +	struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
> +	int port1 = port_dev->portnum;
> +	bool value;
> +	int rc = 0;
> +
> +	if (!hub)
> +		return -EINVAL;
> +
> +	if (hub->in_reset)
> +		return -EBUSY;

What point is there in doing this test?  The value of hub->in_reset may 
change an instant later.  Unless you acquire the hub's lock first.
For that matter, you should be holding the hub's lock while you call 
usb_hub_to_struct_hub() -- unless you don't care if the hub gets 
disconnected while this routine is running.  Or if udev does.

> +
> +	rc = strtobool(buf, &value);
> +	if (rc)
> +		return rc;
> +
> +	if (value)
> +		usb_remote_wakeup(hdev);

Why call usb_remote_wakeup()?  The function was not intended to be used 
this way; it was meant to be used when a device sends a wakeup request.  
Furthermore, nothing prevents the hub from going back into runtime 
suspend the moment this function completes.

If you want to bring a USB device out of runtime suspend, call 
usb_autoresume_device().  And then don't forget to call 
usb_autosuspend_device() when you're done with it.

> +
> +	rc = usb_hub_set_port_power(hdev, hub, port1, value);
> +	if (rc)
> +		return rc;

You probably should acquire the port's lock before doing this.  
Otherwise some other thread might be doing something else to the port at 
the same time.

> +
> +	if (!value) {
> +		usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
> +		if (!port_dev->is_superspeed)
> +			usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);
> +
> +		if (udev) {
> +			port_dev->child = NULL;

That assignment is not necessary; usb_disconnect() will take care of it.

> +			usb_disconnect(&udev);
> +		}
> +	}

Alan Stern

Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Michael Grzeschik]

[-- Attachment #1: Type: text/plain, Size: 7670 bytes --]

Hi!

On Wed, May 11, 2022 at 10:09:26AM -0400, Alan Stern wrote:
>On Wed, May 11, 2022 at 01:13:17AM +0200, Michael Grzeschik wrote:
>> This patch adds an sysfs switch to enable/disable a port on an power
>> switchable hub. It also ensures that the associated device gets
>> disconnected from the logical usb tree.
>
>This says what the patch does.  It does not explain why the patch was
>written or why anybody would want to switch the power on a hub's port.

Good point. This goes together with the missing ABI documentation.
I will fix it in the v2.

>> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
>> ---
>>  drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 47 insertions(+)
>>
>> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
>> index d5bc36ca5b1f77..abc618d87888f3 100644
>> --- a/drivers/usb/core/port.c
>> +++ b/drivers/usb/core/port.c
>> @@ -17,6 +17,52 @@ static int usb_port_block_power_off;
>>
>>  static const struct attribute_group *port_dev_group[];
>>
>> +static ssize_t port_power_store(struct device *dev, struct device_attribute *attr,
>> +			    const char *buf, size_t count)
>> +{
>> +	struct usb_port *port_dev = to_usb_port(dev);
>> +	struct usb_device *udev = port_dev->child;
>> +	struct usb_device *hdev = to_usb_device(dev->parent->parent);
>> +	struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
>> +	int port1 = port_dev->portnum;
>> +	bool value;
>> +	int rc = 0;
>> +
>> +	if (!hub)
>> +		return -EINVAL;
>> +
>> +	if (hub->in_reset)
>> +		return -EBUSY;
>
>What point is there in doing this test?  The value of hub->in_reset may
>change an instant later.  Unless you acquire the hub's lock first.
>For that matter, you should be holding the hub's lock while you call
>usb_hub_to_struct_hub() -- unless you don't care if the hub gets
>disconnected while this routine is running.  Or if udev does.

I could remove it for the sake of simplicity in the first version.
If this will matter in the future we can add it then.

>> +
>> +	rc = strtobool(buf, &value);
>> +	if (rc)
>> +		return rc;
>> +
>> +	if (value)
>> +		usb_remote_wakeup(hdev);
>
>Why call usb_remote_wakeup()?  The function was not intended to be used
>this way; it was meant to be used when a device sends a wakeup request.

I found this function was called when plugging in a device into an
suspended hub. So it seemed to be the right thing to do.

>Furthermore, nothing prevents the hub from going back into runtime
>suspend the moment this function completes.

OK. That needs to be locked than.

Is it with usb_autopm_get_interface and usb_autopm_put_interface?

>If you want to bring a USB device out of runtime suspend, call
>usb_autoresume_device().  And then don't forget to call
>usb_autosuspend_device() when you're done with it.

In case the hub had only one device attached to one one port. When I
called this sysfs function on that port, the hub would suspend
afterwards. Which is probably a correct way to go for a hub with
no active devices attached.

When replacing usb_remote_wakeup with usb_autoresume_device this
works exactly the same. So I will replace it in v2.

The extra usb_autosuspend_device for the hub is probably not necessary.

>> +
>> +	rc = usb_hub_set_port_power(hdev, hub, port1, value);
>> +	if (rc)
>> +		return rc;
>
>You probably should acquire the port's lock before doing this.
>Otherwise some other thread might be doing something else to the port at
>the same time.

Yes. I will do that in v2.

>> +
>> +	if (!value) {
>> +		usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
>> +		if (!port_dev->is_superspeed)
>> +			usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);
>> +
>> +		if (udev) {
>> +			port_dev->child = NULL;
>
>That assignment is not necessary; usb_disconnect() will take care of it.

Here are two things that are in play.

First I have to set port_dev->child = NULL before calling
usb_disconnect. Otherwise the following automatic hub_suspend call (in
case this was the last operational port of the hub) will print the
message "device x-y not suspended yet" and will fail the hub to
suspend.

When calling usb_autoresume_device(udev) instead and before calling
usb_disconnect, this is no longer the case. The hub will be succesfully
suspended.

The second thing is the assignment. I still have to explicitly assign NULL to
port_dev->child. Otherwise a following enable of this port via this sysfs will
run into an hub_event with the usb_disonnect for the device on that port. But
this will spit out a ugly traceback leading with the following error:

[   21.718574] usb 2-1.1: USB disconnect, device number -1

[   21.719100] Unable to handle kernel paging request at virtual address 96d628cc24e2e078
[   21.719807] Mem abort info:
[   21.720065]   ESR = 0x96000044
[   21.720348]   EC = 0x25: DABT (current EL), IL = 32 bits
[   21.720827]   SET = 0, FnV = 0
[   21.721109]   EA = 0, S1PTW = 0
[   21.721447]   FSC = 0x04: level 0 translation fault
[   21.721891] Data abort info:
[   21.722157]   ISV = 0, ISS = 0x00000044
[   21.722505]   CM = 0, WnR = 1
[   21.722779] [96d628cc24e2e078] address between user and kernel address ranges
[   21.723429] Internal error: Oops: 96000044 [#1] PREEMPT SMP
[   21.723927] Modules linked in: uio_pdrv_genirq fuse
[   21.724380] CPU: 0 PID: 58 Comm: kworker/0:3 Not tainted 5.18.0-rc6+ #93
[   21.724977] Hardware name: Radxa ROCK3 Model A (DT)
[   21.725412] Workqueue: usb_hub_wq hub_event
[   21.725802] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   21.726419] pc : usb_disable_endpoint+0x7c/0xdc
[   21.726832] lr : usb_disable_device_endpoints+0xbc/0xe0
[   21.727301] sp : ffffffc009b33b30
[   21.727597] x29: ffffffc009b33b30 x28: ffffff8003ad4ed8 x27: 0000000000000001
[   21.728239] x26: ffffff8004344928 x25: 0000000000000000 x24: ffffffc0096eb8e0
[   21.728885] x23: ffffff80043448a8 x22: ffffff8003961800 x21: 0000000000000001
[   21.729527] x20: 96d628cc24e2e034 x19: ffffff8004344800 x18: ffffffffffffffff
[   21.730168] x17: 0000000000000001 x16: 0000000000000001 x15: ffffffc089b33857
[   21.730810] x14: 0000000000000000 x13: 312d207265626d75 x12: 6e20656369766564
[   21.731452] x11: 00000000fffff7ff x10: 00000000fffff7ff x9 : ffffffc00871b8dc
[   21.732093] x8 : 000000000000bfe8 x7 : ffffffc009b33a38 x6 : 0000000000000001
[   21.732733] x5 : ffffffc009569000 x4 : ffffffc009569050 x3 : ffffff8004344878
[   21.733374] x2 : 0000000000000001 x1 : 000000000000008f x0 : 0000000000000001
[   21.734015] Call trace:
[   21.734235]  usb_disable_endpoint+0x7c/0xdc
[   21.734616]  usb_disable_device_endpoints+0xbc/0xe0
[   21.735054]  usb_disable_device+0x1c0/0x260
[   21.735432]  usb_disconnect+0x108/0x300
[   21.735778]  hub_event+0x1378/0x19c0
[   21.736102]  process_one_work+0x220/0x49c
[   21.736469]  worker_thread+0x154/0x450
[   21.736810]  kthread+0xfc/0x110
[   21.737096]  ret_from_fork+0x10/0x20
[   21.737429] Code: f941c474 340001e0 f901c47f b4ffff14 (b900469f)
[   21.737970] ---[ end trace 0000000000000000 ]---

Did I miss something?

>> +			usb_disconnect(&udev);
>> +		}
>> +	}
>
>Alan Stern

Thanks,
Michael Grzeschik

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Alan Stern]

On Wed, May 11, 2022 at 10:37:27PM +0200, Michael Grzeschik wrote:
> Hi!
> 
> On Wed, May 11, 2022 at 10:09:26AM -0400, Alan Stern wrote:
> > On Wed, May 11, 2022 at 01:13:17AM +0200, Michael Grzeschik wrote:
> > > This patch adds an sysfs switch to enable/disable a port on an power
> > > switchable hub. It also ensures that the associated device gets
> > > disconnected from the logical usb tree.
> > 
> > This says what the patch does.  It does not explain why the patch was
> > written or why anybody would want to switch the power on a hub's port.
> 
> Good point. This goes together with the missing ABI documentation.
> I will fix it in the v2.
> 
> > > Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> > > ---
> > >  drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 47 insertions(+)
> > > 
> > > diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> > > index d5bc36ca5b1f77..abc618d87888f3 100644
> > > --- a/drivers/usb/core/port.c
> > > +++ b/drivers/usb/core/port.c
> > > @@ -17,6 +17,52 @@ static int usb_port_block_power_off;
> > > 
> > >  static const struct attribute_group *port_dev_group[];
> > > 
> > > +static ssize_t port_power_store(struct device *dev, struct device_attribute *attr,
> > > +			    const char *buf, size_t count)
> > > +{
> > > +	struct usb_port *port_dev = to_usb_port(dev);
> > > +	struct usb_device *udev = port_dev->child;
> > > +	struct usb_device *hdev = to_usb_device(dev->parent->parent);
> > > +	struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
> > > +	int port1 = port_dev->portnum;
> > > +	bool value;
> > > +	int rc = 0;
> > > +
> > > +	if (!hub)
> > > +		return -EINVAL;
> > > +
> > > +	if (hub->in_reset)
> > > +		return -EBUSY;
> > 
> > What point is there in doing this test?  The value of hub->in_reset may
> > change an instant later.  Unless you acquire the hub's lock first.
> > For that matter, you should be holding the hub's lock while you call
> > usb_hub_to_struct_hub() -- unless you don't care if the hub gets
> > disconnected while this routine is running.  Or if udev does.
> 
> I could remove it for the sake of simplicity in the first version.
> If this will matter in the future we can add it then.
> 
> > > +
> > > +	rc = strtobool(buf, &value);
> > > +	if (rc)
> > > +		return rc;
> > > +
> > > +	if (value)
> > > +		usb_remote_wakeup(hdev);
> > 
> > Why call usb_remote_wakeup()?  The function was not intended to be used
> > this way; it was meant to be used when a device sends a wakeup request.
> 
> I found this function was called when plugging in a device into an
> suspended hub. So it seemed to be the right thing to do.

That's because the hub sent a remote wakeup signal when the device was 
plugged in.  In your case there is no remote wakeup signal.

> > Furthermore, nothing prevents the hub from going back into runtime
> > suspend the moment this function completes.
> 
> OK. That needs to be locked than.
> 
> Is it with usb_autopm_get_interface and usb_autopm_put_interface?

Yes.  Read the kerneldoc for those routines.

> > If you want to bring a USB device out of runtime suspend, call
> > usb_autoresume_device().  And then don't forget to call
> > usb_autosuspend_device() when you're done with it.
> 
> In case the hub had only one device attached to one one port. When I
> called this sysfs function on that port, the hub would suspend
> afterwards. Which is probably a correct way to go for a hub with
> no active devices attached.
> 
> When replacing usb_remote_wakeup with usb_autoresume_device this
> works exactly the same. So I will replace it in v2.
> 
> The extra usb_autosuspend_device for the hub is probably not necessary.

If you don't call usb_autosuspend_device after doing 
usb_autoresume_device then the hub will never go into runtime suspend.

> > > +	rc = usb_hub_set_port_power(hdev, hub, port1, value);
> > > +	if (rc)
> > > +		return rc;
> > 
> > You probably should acquire the port's lock before doing this.
> > Otherwise some other thread might be doing something else to the port at
> > the same time.
> 
> Yes. I will do that in v2.
> 
> > > +
> > > +	if (!value) {
> > > +		usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
> > > +		if (!port_dev->is_superspeed)
> > > +			usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);
> > > +
> > > +		if (udev) {
> > > +			port_dev->child = NULL;
> > 
> > That assignment is not necessary; usb_disconnect() will take care of it.
> 
> Here are two things that are in play.
> 
> First I have to set port_dev->child = NULL before calling
> usb_disconnect. Otherwise the following automatic hub_suspend call (in
> case this was the last operational port of the hub) will print the
> message "device x-y not suspended yet" and will fail the hub to
> suspend.
> 
> When calling usb_autoresume_device(udev) instead and before calling
> usb_disconnect, this is no longer the case. The hub will be succesfully
> suspended.
> 
> The second thing is the assignment. I still have to explicitly assign NULL to
> port_dev->child. Otherwise a following enable of this port via this sysfs will
> run into an hub_event with the usb_disonnect for the device on that port. But
> this will spit out a ugly traceback leading with the following error:
> 
> [   21.718574] usb 2-1.1: USB disconnect, device number -1
> 
> [   21.719100] Unable to handle kernel paging request at virtual address 96d628cc24e2e078
> [   21.719807] Mem abort info:
> [   21.720065]   ESR = 0x96000044
> [   21.720348]   EC = 0x25: DABT (current EL), IL = 32 bits
> [   21.720827]   SET = 0, FnV = 0
> [   21.721109]   EA = 0, S1PTW = 0
> [   21.721447]   FSC = 0x04: level 0 translation fault
> [   21.721891] Data abort info:
> [   21.722157]   ISV = 0, ISS = 0x00000044
> [   21.722505]   CM = 0, WnR = 1
> [   21.722779] [96d628cc24e2e078] address between user and kernel address ranges
> [   21.723429] Internal error: Oops: 96000044 [#1] PREEMPT SMP
> [   21.723927] Modules linked in: uio_pdrv_genirq fuse
> [   21.724380] CPU: 0 PID: 58 Comm: kworker/0:3 Not tainted 5.18.0-rc6+ #93
> [   21.724977] Hardware name: Radxa ROCK3 Model A (DT)
> [   21.725412] Workqueue: usb_hub_wq hub_event
> [   21.725802] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   21.726419] pc : usb_disable_endpoint+0x7c/0xdc
> [   21.726832] lr : usb_disable_device_endpoints+0xbc/0xe0
> [   21.727301] sp : ffffffc009b33b30
> [   21.727597] x29: ffffffc009b33b30 x28: ffffff8003ad4ed8 x27: 0000000000000001
> [   21.728239] x26: ffffff8004344928 x25: 0000000000000000 x24: ffffffc0096eb8e0
> [   21.728885] x23: ffffff80043448a8 x22: ffffff8003961800 x21: 0000000000000001
> [   21.729527] x20: 96d628cc24e2e034 x19: ffffff8004344800 x18: ffffffffffffffff
> [   21.730168] x17: 0000000000000001 x16: 0000000000000001 x15: ffffffc089b33857
> [   21.730810] x14: 0000000000000000 x13: 312d207265626d75 x12: 6e20656369766564
> [   21.731452] x11: 00000000fffff7ff x10: 00000000fffff7ff x9 : ffffffc00871b8dc
> [   21.732093] x8 : 000000000000bfe8 x7 : ffffffc009b33a38 x6 : 0000000000000001
> [   21.732733] x5 : ffffffc009569000 x4 : ffffffc009569050 x3 : ffffff8004344878
> [   21.733374] x2 : 0000000000000001 x1 : 000000000000008f x0 : 0000000000000001
> [   21.734015] Call trace:
> [   21.734235]  usb_disable_endpoint+0x7c/0xdc
> [   21.734616]  usb_disable_device_endpoints+0xbc/0xe0
> [   21.735054]  usb_disable_device+0x1c0/0x260
> [   21.735432]  usb_disconnect+0x108/0x300
> [   21.735778]  hub_event+0x1378/0x19c0
> [   21.736102]  process_one_work+0x220/0x49c
> [   21.736469]  worker_thread+0x154/0x450
> [   21.736810]  kthread+0xfc/0x110
> [   21.737096]  ret_from_fork+0x10/0x20
> [   21.737429] Code: f941c474 340001e0 f901c47f b4ffff14 (b900469f)
> [   21.737970] ---[ end trace 0000000000000000 ]---
> 
> Did I miss something?

No: You found a real bug in the hub driver!  usb_disconnect() really 
is supposed to set port_dev->child to NULL at some point, but it 
doesn't.  In fact, port_dev->child never gets set back to NULL (except 
in the trivial case where a newly attached device fails to initialize 
and enumerate).

I'll work on a patch to fix this, and I'll CC: you when it's ready.

Alan Stern

Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Alan Stern]

On Wed, May 11, 2022 at 09:19:57PM -0400, Alan Stern wrote:
> On Wed, May 11, 2022 at 10:37:27PM +0200, Michael Grzeschik wrote:

> > > > +		if (udev) {
> > > > +			port_dev->child = NULL;
> > > 
> > > That assignment is not necessary; usb_disconnect() will take care of it.
> > 
> > Here are two things that are in play.
> > 
> > First I have to set port_dev->child = NULL before calling
> > usb_disconnect. Otherwise the following automatic hub_suspend call (in
> > case this was the last operational port of the hub) will print the
> > message "device x-y not suspended yet" and will fail the hub to
> > suspend.
> > 
> > When calling usb_autoresume_device(udev) instead and before calling
> > usb_disconnect, this is no longer the case. The hub will be succesfully
> > suspended.
> > 
> > The second thing is the assignment. I still have to explicitly assign NULL to
> > port_dev->child. Otherwise a following enable of this port via this sysfs will
> > run into an hub_event with the usb_disonnect for the device on that port. But
> > this will spit out a ugly traceback leading with the following error:
> > 
> > [   21.718574] usb 2-1.1: USB disconnect, device number -1
> > 
> > [   21.719100] Unable to handle kernel paging request at virtual address 96d628cc24e2e078
> > [   21.719807] Mem abort info:
> > [   21.720065]   ESR = 0x96000044
> > [   21.720348]   EC = 0x25: DABT (current EL), IL = 32 bits
> > [   21.720827]   SET = 0, FnV = 0
> > [   21.721109]   EA = 0, S1PTW = 0
> > [   21.721447]   FSC = 0x04: level 0 translation fault
> > [   21.721891] Data abort info:
> > [   21.722157]   ISV = 0, ISS = 0x00000044
> > [   21.722505]   CM = 0, WnR = 1
> > [   21.722779] [96d628cc24e2e078] address between user and kernel address ranges
> > [   21.723429] Internal error: Oops: 96000044 [#1] PREEMPT SMP
> > [   21.723927] Modules linked in: uio_pdrv_genirq fuse
> > [   21.724380] CPU: 0 PID: 58 Comm: kworker/0:3 Not tainted 5.18.0-rc6+ #93
> > [   21.724977] Hardware name: Radxa ROCK3 Model A (DT)
> > [   21.725412] Workqueue: usb_hub_wq hub_event
> > [   21.725802] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [   21.726419] pc : usb_disable_endpoint+0x7c/0xdc
> > [   21.726832] lr : usb_disable_device_endpoints+0xbc/0xe0
> > [   21.727301] sp : ffffffc009b33b30
> > [   21.727597] x29: ffffffc009b33b30 x28: ffffff8003ad4ed8 x27: 0000000000000001
> > [   21.728239] x26: ffffff8004344928 x25: 0000000000000000 x24: ffffffc0096eb8e0
> > [   21.728885] x23: ffffff80043448a8 x22: ffffff8003961800 x21: 0000000000000001
> > [   21.729527] x20: 96d628cc24e2e034 x19: ffffff8004344800 x18: ffffffffffffffff
> > [   21.730168] x17: 0000000000000001 x16: 0000000000000001 x15: ffffffc089b33857
> > [   21.730810] x14: 0000000000000000 x13: 312d207265626d75 x12: 6e20656369766564
> > [   21.731452] x11: 00000000fffff7ff x10: 00000000fffff7ff x9 : ffffffc00871b8dc
> > [   21.732093] x8 : 000000000000bfe8 x7 : ffffffc009b33a38 x6 : 0000000000000001
> > [   21.732733] x5 : ffffffc009569000 x4 : ffffffc009569050 x3 : ffffff8004344878
> > [   21.733374] x2 : 0000000000000001 x1 : 000000000000008f x0 : 0000000000000001
> > [   21.734015] Call trace:
> > [   21.734235]  usb_disable_endpoint+0x7c/0xdc
> > [   21.734616]  usb_disable_device_endpoints+0xbc/0xe0
> > [   21.735054]  usb_disable_device+0x1c0/0x260
> > [   21.735432]  usb_disconnect+0x108/0x300
> > [   21.735778]  hub_event+0x1378/0x19c0
> > [   21.736102]  process_one_work+0x220/0x49c
> > [   21.736469]  worker_thread+0x154/0x450
> > [   21.736810]  kthread+0xfc/0x110
> > [   21.737096]  ret_from_fork+0x10/0x20
> > [   21.737429] Code: f941c474 340001e0 f901c47f b4ffff14 (b900469f)
> > [   21.737970] ---[ end trace 0000000000000000 ]---
> > 
> > Did I miss something?
> 
> No: You found a real bug in the hub driver!  usb_disconnect() really 
> is supposed to set port_dev->child to NULL at some point, but it 
> doesn't.  In fact, port_dev->child never gets set back to NULL (except 
> in the trivial case where a newly attached device fails to initialize 
> and enumerate).
> 
> I'll work on a patch to fix this, and I'll CC: you when it's ready.

I take it back.  This isn't a bug; it's a mistake in the way you called 
usb_disconnect().  Your patch did:

		if (udev) {
			port_dev->child = NULL;
			usb_disconnect(&udev);
		}

The argument to usb_disconnect() is supposed to be &port_dev->child, not 
&udev.  You can see near the end of the function that it sets *pdev to 
NULL; this is where port_dev->child gets cleared.

Not incidentally, usb_disconnect() requires that you hold hdev's device 
lock when you call it (this is mentioned in the kerneldoc, although the 
requirement that pdev points to port_dev->child isn't -- the kerneldoc 
for that function could stand to be improved).

Alan Stern

Re: [PATCH] usb: hub: port: add sysfs entry to switch port power

[Michael Grzeschik]

[-- Attachment #1: Type: text/plain, Size: 5534 bytes --]

On Sat, May 14, 2022 at 03:52:25PM -0400, Alan Stern wrote:
>On Wed, May 11, 2022 at 09:19:57PM -0400, Alan Stern wrote:
>> On Wed, May 11, 2022 at 10:37:27PM +0200, Michael Grzeschik wrote:
>
>> > > > +		if (udev) {
>> > > > +			port_dev->child = NULL;
>> > >
>> > > That assignment is not necessary; usb_disconnect() will take care of it.
>> >
>> > Here are two things that are in play.
>> >
>> > First I have to set port_dev->child = NULL before calling
>> > usb_disconnect. Otherwise the following automatic hub_suspend call (in
>> > case this was the last operational port of the hub) will print the
>> > message "device x-y not suspended yet" and will fail the hub to
>> > suspend.
>> >
>> > When calling usb_autoresume_device(udev) instead and before calling
>> > usb_disconnect, this is no longer the case. The hub will be succesfully
>> > suspended.
>> >
>> > The second thing is the assignment. I still have to explicitly assign NULL to
>> > port_dev->child. Otherwise a following enable of this port via this sysfs will
>> > run into an hub_event with the usb_disonnect for the device on that port. But
>> > this will spit out a ugly traceback leading with the following error:
>> >
>> > [   21.718574] usb 2-1.1: USB disconnect, device number -1
>> >
>> > [   21.719100] Unable to handle kernel paging request at virtual address 96d628cc24e2e078
>> > [   21.719807] Mem abort info:
>> > [   21.720065]   ESR = 0x96000044
>> > [   21.720348]   EC = 0x25: DABT (current EL), IL = 32 bits
>> > [   21.720827]   SET = 0, FnV = 0
>> > [   21.721109]   EA = 0, S1PTW = 0
>> > [   21.721447]   FSC = 0x04: level 0 translation fault
>> > [   21.721891] Data abort info:
>> > [   21.722157]   ISV = 0, ISS = 0x00000044
>> > [   21.722505]   CM = 0, WnR = 1
>> > [   21.722779] [96d628cc24e2e078] address between user and kernel address ranges
>> > [   21.723429] Internal error: Oops: 96000044 [#1] PREEMPT SMP
>> > [   21.723927] Modules linked in: uio_pdrv_genirq fuse
>> > [   21.724380] CPU: 0 PID: 58 Comm: kworker/0:3 Not tainted 5.18.0-rc6+ #93
>> > [   21.724977] Hardware name: Radxa ROCK3 Model A (DT)
>> > [   21.725412] Workqueue: usb_hub_wq hub_event
>> > [   21.725802] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> > [   21.726419] pc : usb_disable_endpoint+0x7c/0xdc
>> > [   21.726832] lr : usb_disable_device_endpoints+0xbc/0xe0
>> > [   21.727301] sp : ffffffc009b33b30
>> > [   21.727597] x29: ffffffc009b33b30 x28: ffffff8003ad4ed8 x27: 0000000000000001
>> > [   21.728239] x26: ffffff8004344928 x25: 0000000000000000 x24: ffffffc0096eb8e0
>> > [   21.728885] x23: ffffff80043448a8 x22: ffffff8003961800 x21: 0000000000000001
>> > [   21.729527] x20: 96d628cc24e2e034 x19: ffffff8004344800 x18: ffffffffffffffff
>> > [   21.730168] x17: 0000000000000001 x16: 0000000000000001 x15: ffffffc089b33857
>> > [   21.730810] x14: 0000000000000000 x13: 312d207265626d75 x12: 6e20656369766564
>> > [   21.731452] x11: 00000000fffff7ff x10: 00000000fffff7ff x9 : ffffffc00871b8dc
>> > [   21.732093] x8 : 000000000000bfe8 x7 : ffffffc009b33a38 x6 : 0000000000000001
>> > [   21.732733] x5 : ffffffc009569000 x4 : ffffffc009569050 x3 : ffffff8004344878
>> > [   21.733374] x2 : 0000000000000001 x1 : 000000000000008f x0 : 0000000000000001
>> > [   21.734015] Call trace:
>> > [   21.734235]  usb_disable_endpoint+0x7c/0xdc
>> > [   21.734616]  usb_disable_device_endpoints+0xbc/0xe0
>> > [   21.735054]  usb_disable_device+0x1c0/0x260
>> > [   21.735432]  usb_disconnect+0x108/0x300
>> > [   21.735778]  hub_event+0x1378/0x19c0
>> > [   21.736102]  process_one_work+0x220/0x49c
>> > [   21.736469]  worker_thread+0x154/0x450
>> > [   21.736810]  kthread+0xfc/0x110
>> > [   21.737096]  ret_from_fork+0x10/0x20
>> > [   21.737429] Code: f941c474 340001e0 f901c47f b4ffff14 (b900469f)
>> > [   21.737970] ---[ end trace 0000000000000000 ]---
>> >
>> > Did I miss something?
>>
>> No: You found a real bug in the hub driver!  usb_disconnect() really
>> is supposed to set port_dev->child to NULL at some point, but it
>> doesn't.  In fact, port_dev->child never gets set back to NULL (except
>> in the trivial case where a newly attached device fails to initialize
>> and enumerate).
>>
>> I'll work on a patch to fix this, and I'll CC: you when it's ready.
>
>I take it back.  This isn't a bug; it's a mistake in the way you called
>usb_disconnect().  Your patch did:
>
>		if (udev) {
>			port_dev->child = NULL;
>			usb_disconnect(&udev);
>		}
>
>The argument to usb_disconnect() is supposed to be &port_dev->child, not
>&udev.  You can see near the end of the function that it sets *pdev to
>NULL; this is where port_dev->child gets cleared.

Thanks for the clarification.

>Not incidentally, usb_disconnect() requires that you hold hdev's device
>lock when you call it (this is mentioned in the kerneldoc, although the
>requirement that pdev points to port_dev->child isn't -- the kerneldoc
>for that function could stand to be improved).

Okay. I added the lock around the usb_disconnect.

I just added some tweaks regarding the pm handling and will send out v2.

Regards,
Michael

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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