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[PATCH v7 5/5] usb: doc: add document for USB3 debug port usage

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  [PATCH v7 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu <baolu.lu@linux.intel.com> - 2017-02-14 03:30 +0100
    Re: [PATCH v7 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu <baolu.lu@linux.intel.com> - 2017-02-14 05:50 +0100
      RE: [PATCH v7 5/5] usb: doc: add document for USB3 debug port usage Peter Chen <peter.chen@nxp.com> - 2017-02-14 07:20 +0100
        Re: [PATCH v7 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu <baolu.lu@linux.intel.com> - 2017-02-14 08:30 +0100

#1580231 — [PATCH v7 5/5] usb: doc: add document for USB3 debug port usage

Add Documentation/usb/usb3-debug-port.rst. This document includes
the user guide for USB3 debug port.

Cc: linux-doc@vger.kernel.org
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 Documentation/usb/usb3-debug-port.rst | 98 +++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 Documentation/usb/usb3-debug-port.rst

diff --git a/Documentation/usb/usb3-debug-port.rst b/Documentation/usb/usb3-debug-port.rst
new file mode 100644
index 0000000..9eddb3a
--- /dev/null
+++ b/Documentation/usb/usb3-debug-port.rst
@@ -0,0 +1,98 @@
+===============
+USB3 debug port
+===============
+
+:Author: Lu Baolu <baolu.lu@linux.intel.com>
+:Date: January 2017
+
+GENERAL
+=======
+
+This is a HOWTO for using USB3 debug port on x86 systems.
+
+Before using any kernel debugging functionality based on USB3
+debug port, you need to check 1) whether debug port is supported
+by the xHCI host; 2) which port is used for debugging purposes
+(normally the first USB3 root port). You must have a USB 3.0
+super-speed A-to-A debugging cable to connect the debug target
+with a debug host. In this document, "debug target" stands for
+the system under debugging, and "debug host" stands for a
+stand-alone system that is able to talk to the debugging target
+through the USB3 debug port.
+
+EARLY PRINTK
+============
+
+On the debug target system, you need to customize a debugging
+kernel with CONFIG_EARLY_PRINTK_USB_XDBC enabled. And, add
+below kernel boot parameter::
+
+	"earlyprintk=xdbc"
+
+If there are multiple xHCI controllers in the system, you can
+append a host contoller index to this kernel parameter. This
+index starts from 0.
+
+If you are going to use the "keep" option defined by the
+early printk framework to keep the boot console alive after
+early boot, you'd better add below kernel boot parameter::
+
+	"usbcore.autosuspend=-1"
+
+On the debug host side, you don't need to customize the kernel,
+but you'd better disable usb subsystem runtime power management
+by adding below kernel boot parameter::
+
+	"usbcore.autosuspend=-1"
+
+Before starting the debug target, you should connect the debug
+port on the debug target with a root port or port of any external
+hub on the debug host. The cable used to connect these two ports
+should be a USB 3.0 super-speed A-to-A debugging cable.
+
+During early boot of the debug target, DbC (xHCI debug engine for
+USB3 debug port) hardware will be detected and initialized. After
+initialization, the debug host should be able to enumerate the
+debug target as a debug device. The debug host will then bind the
+debug device with the usb_debug driver module and create the
+/dev/ttyUSB0 device.
+
+If the debug device enumeration goes smoothly, you should be able
+to see below kernel messages on the debug host::
+
+	# tail -f /var/log/kern.log
+	[ 1815.983374] usb 4-3: new SuperSpeed USB device number 4 using xhci_hcd
+	[ 1815.999595] usb 4-3: LPM exit latency is zeroed, disabling LPM.
+	[ 1815.999899] usb 4-3: New USB device found, idVendor=1d6b, idProduct=0004
+	[ 1815.999902] usb 4-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
+	[ 1815.999903] usb 4-3: Product: Remote GDB
+	[ 1815.999904] usb 4-3: Manufacturer: Linux
+	[ 1815.999905] usb 4-3: SerialNumber: 0001
+	[ 1816.000240] usb_debug 4-3:1.0: xhci_dbc converter detected
+	[ 1816.000360] usb 4-3: xhci_dbc converter now attached to ttyUSB0
+
+You can run below bash scripts on the debug host to read the kernel
+log sent from debug target.
+
+.. code-block:: sh
+
+	===== start of bash scripts =============
+	#!/bin/bash
+
+	while true ; do
+		while [ ! -d /sys/class/tty/ttyUSB0 ] ; do
+			:
+	done
+	cat /dev/ttyUSB0 >> xdbc.log
+	done
+	===== end of bash scripts ===============
+
+You should be able to see the early boot message in xdbc.log.
+
+If it doesn't work, please ask it on the <linux-usb@vger.kernel.org>
+mailing list.
+
+Below USB hosts have been verified to work::
+
+	Intel Corporation Sunrise Point-H USB 3.0 xHCI Controller
+	Intel Corporation Wildcat Point-LP USB xHCI Controller
-- 
2.1.4

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#1580294

Hi,

On 02/14/2017 11:45 AM, Peter Chen wrote:
> On Tue, Feb 14, 2017 at 10:27 AM, Lu Baolu <baolu.lu@linux.intel.com> wrote:
>
>> Add Documentation/usb/usb3-debug-port.rst. This document includes
>> the user guide for USB3 debug port.
>>
>> Cc: linux-doc@vger.kernel.org
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>>  Documentation/usb/usb3-debug-port.rst | 98 ++++++++++++++++++++++++++++++
>> +++++
>>  1 file changed, 98 insertions(+)
>>  create mode 100644 Documentation/usb/usb3-debug-port.rst
>>
>> diff --git a/Documentation/usb/usb3-debug-port.rst
>> b/Documentation/usb/usb3-debug-port.rst
>> new file mode 100644
>> index 0000000..9eddb3a
>> --- /dev/null
>> +++ b/Documentation/usb/usb3-debug-port.rst
>> @@ -0,0 +1,98 @@
>> +===============
>> +USB3 debug port
>> +===============
>> +
>> +:Author: Lu Baolu <baolu.lu@linux.intel.com>
>> +:Date: January 2017
>> +
>> +GENERAL
>> +=======
>> +
>> +This is a HOWTO for using USB3 debug port on x86 systems.
>> +
>> +Before using any kernel debugging functionality based on USB3
>> +debug port, you need to check 1) whether debug port is supported
>> +by the xHCI host; 2) which port is used for debugging purposes
>> +(normally the first USB3 root port). You must have a USB 3.0
>> +super-speed A-to-A debugging cable to connect the debug target
>> +with a debug host. In this document, "debug target" stands for
>> +the system under debugging, and "debug host" stands for a
>> +stand-alone system that is able to talk to the debugging target
>> +through the USB3 debug port.
>> +
>> +EARLY PRINTK
>> +============
>> +
>> +On the debug target system, you need to customize a debugging
>> +kernel with CONFIG_EARLY_PRINTK_USB_XDBC enabled. And, add
>> +below kernel boot parameter::
>> +
>> +       "earlyprintk=xdbc"
>> +
>> +If there are multiple xHCI controllers in the system, you can
>> +append a host contoller index to this kernel parameter. This
>> +index starts from 0.
>> +
>> +If you are going to use the "keep" option defined by the
>> +early printk framework to keep the boot console alive after
>> +early boot, you'd better add below kernel boot parameter::
>> +
>> +       "usbcore.autosuspend=-1"
>> +
>> +On the debug host side, you don't need to customize the kernel,
>> +but you'd better disable usb subsystem runtime power management
>> +by adding below kernel boot parameter::
>> +
>> +       "usbcore.autosuspend=-1"
>> +
>>
> Just curious, why autosuspend needs to be disabled for this function?

This implementation doesn't support suspend/resume yet.

Best regards,
Lu Baolu

>
> BR,
> Peter Chen
>

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#1580320

 
>
>On 02/14/2017 11:45 AM, Peter Chen wrote:
>> On Tue, Feb 14, 2017 at 10:27 AM, Lu Baolu <baolu.lu@linux.intel.com> wrote:
>>
>>> Add Documentation/usb/usb3-debug-port.rst. This document includes the
>>> user guide for USB3 debug port.
>>>
>>> Cc: linux-doc@vger.kernel.org
>>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>>> ---
>>>  Documentation/usb/usb3-debug-port.rst | 98
>>> ++++++++++++++++++++++++++++++
>>> +++++
>>>  1 file changed, 98 insertions(+)
>>>  create mode 100644 Documentation/usb/usb3-debug-port.rst
>>>
>>> diff --git a/Documentation/usb/usb3-debug-port.rst
>>> b/Documentation/usb/usb3-debug-port.rst
>>> new file mode 100644
>>> index 0000000..9eddb3a
>>> --- /dev/null
>>> +++ b/Documentation/usb/usb3-debug-port.rst
>>> @@ -0,0 +1,98 @@
>>> +===============
>>> +USB3 debug port
>>> +===============
>>> +
>>> +:Author: Lu Baolu <baolu.lu@linux.intel.com>
>>> +:Date: January 2017
>>> +
>>> +GENERAL
>>> +=======
>>> +
>>> +This is a HOWTO for using USB3 debug port on x86 systems.
>>> +
>>> +Before using any kernel debugging functionality based on USB3 debug
>>> +port, you need to check 1) whether debug port is supported by the
>>> +xHCI host; 2) which port is used for debugging purposes (normally
>>> +the first USB3 root port). You must have a USB 3.0 super-speed
>>> +A-to-A debugging cable to connect the debug target with a debug
>>> +host. In this document, "debug target" stands for the system under
>>> +debugging, and "debug host" stands for a stand-alone system that is
>>> +able to talk to the debugging target through the USB3 debug port.
>>> +
>>> +EARLY PRINTK
>>> +============
>>> +
>>> +On the debug target system, you need to customize a debugging kernel
>>> +with CONFIG_EARLY_PRINTK_USB_XDBC enabled. And, add below kernel
>>> +boot parameter::
>>> +
>>> +       "earlyprintk=xdbc"
>>> +
>>> +If there are multiple xHCI controllers in the system, you can append
>>> +a host contoller index to this kernel parameter. This index starts
>>> +from 0.
>>> +
>>> +If you are going to use the "keep" option defined by the early
>>> +printk framework to keep the boot console alive after early boot,
>>> +you'd better add below kernel boot parameter::
>>> +
>>> +       "usbcore.autosuspend=-1"
>>> +
>>> +On the debug host side, you don't need to customize the kernel, but
>>> +you'd better disable usb subsystem runtime power management by
>>> +adding below kernel boot parameter::
>>> +
>>> +       "usbcore.autosuspend=-1"
>>> +
>>>
>> Just curious, why autosuspend needs to be disabled for this function?
>
>This implementation doesn't support suspend/resume yet.
 
Why host side needs to disable it too?

Peter

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#1580360

Hi,

On 02/14/2017 02:13 PM, Peter Chen wrote:
>  
>> On 02/14/2017 11:45 AM, Peter Chen wrote:
>>> On Tue, Feb 14, 2017 at 10:27 AM, Lu Baolu <baolu.lu@linux.intel.com> wrote:
>>>
>>>> Add Documentation/usb/usb3-debug-port.rst. This document includes the
>>>> user guide for USB3 debug port.
>>>>
>>>> Cc: linux-doc@vger.kernel.org
>>>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>>>> ---
>>>>  Documentation/usb/usb3-debug-port.rst | 98
>>>> ++++++++++++++++++++++++++++++
>>>> +++++
>>>>  1 file changed, 98 insertions(+)
>>>>  create mode 100644 Documentation/usb/usb3-debug-port.rst
>>>>
>>>> diff --git a/Documentation/usb/usb3-debug-port.rst
>>>> b/Documentation/usb/usb3-debug-port.rst
>>>> new file mode 100644
>>>> index 0000000..9eddb3a
>>>> --- /dev/null
>>>> +++ b/Documentation/usb/usb3-debug-port.rst
>>>> @@ -0,0 +1,98 @@
>>>> +===============
>>>> +USB3 debug port
>>>> +===============
>>>> +
>>>> +:Author: Lu Baolu <baolu.lu@linux.intel.com>
>>>> +:Date: January 2017
>>>> +
>>>> +GENERAL
>>>> +=======
>>>> +
>>>> +This is a HOWTO for using USB3 debug port on x86 systems.
>>>> +
>>>> +Before using any kernel debugging functionality based on USB3 debug
>>>> +port, you need to check 1) whether debug port is supported by the
>>>> +xHCI host; 2) which port is used for debugging purposes (normally
>>>> +the first USB3 root port). You must have a USB 3.0 super-speed
>>>> +A-to-A debugging cable to connect the debug target with a debug
>>>> +host. In this document, "debug target" stands for the system under
>>>> +debugging, and "debug host" stands for a stand-alone system that is
>>>> +able to talk to the debugging target through the USB3 debug port.
>>>> +
>>>> +EARLY PRINTK
>>>> +============
>>>> +
>>>> +On the debug target system, you need to customize a debugging kernel
>>>> +with CONFIG_EARLY_PRINTK_USB_XDBC enabled. And, add below kernel
>>>> +boot parameter::
>>>> +
>>>> +       "earlyprintk=xdbc"
>>>> +
>>>> +If there are multiple xHCI controllers in the system, you can append
>>>> +a host contoller index to this kernel parameter. This index starts
>>>> +from 0.
>>>> +
>>>> +If you are going to use the "keep" option defined by the early
>>>> +printk framework to keep the boot console alive after early boot,
>>>> +you'd better add below kernel boot parameter::
>>>> +
>>>> +       "usbcore.autosuspend=-1"
>>>> +
>>>> +On the debug host side, you don't need to customize the kernel, but
>>>> +you'd better disable usb subsystem runtime power management by
>>>> +adding below kernel boot parameter::
>>>> +
>>>> +       "usbcore.autosuspend=-1"
>>>> +
>>>>
>>> Just curious, why autosuspend needs to be disabled for this function?
>> This implementation doesn't support suspend/resume yet.
>  
> Why host side needs to disable it too?

If host side runtime suspend/resume is enabled, it might ask the
debug device to suspend. This will cause the debug device dead.

The suspend/resume of the debug device depends on xhci driver.
I will make it happen in separated patches with more tests. It's in
my TODO list.

Best regards,
Lu Baolu

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