[PATCH v2] usb: hub: try old enumeration scheme first for high speed devices

[PATCH v2] usb: hub: try old enumeration scheme first for high speed devices

[Zeng Tao]

The new scheme is required just to support legacy low and full-speed
devices. For high speed devices, it will slower the enumeration speed.
So in this patch we try the "old" enumeration scheme first for high speed
devices, and this is what Windows does since Windows 8.

Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
---
Changes in v2:
1. As suggested by Alan, mention in the commit log that this change is
follow what the Window does.
2. As suggested by Roger, update the kernel-parameter description.
---
 Documentation/admin-guide/kernel-parameters.txt | 3 ++-
 drivers/usb/core/hub.c                          | 5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 533ff5c..95db23c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4453,7 +4453,8 @@
 
 	usbcore.old_scheme_first=
 			[USB] Start with the old device initialization
-			scheme (default 0 = off).
+			scheme,  applies only to low and full-speed devices
+			 (default 0 = off).
 
 	usbcore.usbfs_memory_mb=
 			[USB] Memory limit (in MB) for buffers allocated by
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 1fb2668..d265b19 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2661,10 +2661,13 @@ static bool use_new_scheme(struct usb_device *udev, int retry,
 	int old_scheme_first_port =
 		port_dev->quirks & USB_PORT_QUIRK_OLD_SCHEME;
 
+	int quick_enumeration = (udev->speed == USB_SPEED_HIGH);
+
 	if (udev->speed >= USB_SPEED_SUPER)
 		return false;
 
-	return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first);
+	return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first
+			      || quick_enumeration);
 }
 
 /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
-- 
2.7.4

Re: [PATCH v2] usb: hub: try old enumeration scheme first for high speed devices

[Alan Stern]

On Fri, 17 Aug 2018, Zeng Tao wrote:

> The new scheme is required just to support legacy low and full-speed
> devices. For high speed devices, it will slower the enumeration speed.
> So in this patch we try the "old" enumeration scheme first for high speed
> devices, and this is what Windows does since Windows 8.
> 
> Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
> ---
> Changes in v2:
> 1. As suggested by Alan, mention in the commit log that this change is
> follow what the Window does.
> 2. As suggested by Roger, update the kernel-parameter description.
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 3 ++-
>  drivers/usb/core/hub.c                          | 5 ++++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 533ff5c..95db23c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4453,7 +4453,8 @@
>  
>  	usbcore.old_scheme_first=
>  			[USB] Start with the old device initialization
> -			scheme (default 0 = off).
> +			scheme,  applies only to low and full-speed devices
> +			 (default 0 = off).
>  
>  	usbcore.usbfs_memory_mb=
>  			[USB] Memory limit (in MB) for buffers allocated by
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 1fb2668..d265b19 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2661,10 +2661,13 @@ static bool use_new_scheme(struct usb_device *udev, int retry,
>  	int old_scheme_first_port =
>  		port_dev->quirks & USB_PORT_QUIRK_OLD_SCHEME;
>  
> +	int quick_enumeration = (udev->speed == USB_SPEED_HIGH);

Minor style point: the preceding blank line should be eliminated.

> +
>  	if (udev->speed >= USB_SPEED_SUPER)
>  		return false;
>  
> -	return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first);
> +	return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first
> +			      || quick_enumeration);
>  }
>  
>  /* Is a USB 3.0 port in the Inactive or Compliance Mode state?

Aside from that:

Acked-by: Alan Stern <stern@rowland.harvard.edu>

RE: [PATCH v2] usb: hub: try old enumeration scheme first for high speed devices

[Zengtao (B)]

Hi Alan:

Thanks for your reply.

>-----Original Message-----
>From: Alan Stern [mailto:stern@rowland.harvard.edu]
>Sent: Friday, August 17, 2018 10:19 PM
>To: Zengtao (B) <prime.zeng@hisilicon.com>
>Cc: gregkh@linuxfoundation.org; mathias.nyman@linux.intel.com;
>drinkcat@chromium.org; felipe.balbi@linux.intel.com;
>drake@endlessm.com; mike.looijmans@topic.nl; joe@perches.com;
>Jonathan Corbet <corbet@lwn.net>; Thomas Gleixner <tglx@linutronix.de>;
>Ingo Molnar <mingo@kernel.org>; Rafael J. Wysocki
><rafael.j.wysocki@intel.com>; Marc Zyngier <marc.zyngier@arm.com>;
>Kai-Heng Feng <kai.heng.feng@canonical.com>; Thymo van Beers
><thymovanbeers@gmail.com>; Frederic Weisbecker <frederic@kernel.org>;
>Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>; David Rientjes
><rientjes@google.com>; linux-doc@vger.kernel.org;
>linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org
>Subject: Re: [PATCH v2] usb: hub: try old enumeration scheme first for high
>speed devices
>
>On Fri, 17 Aug 2018, Zeng Tao wrote:
>
>> The new scheme is required just to support legacy low and full-speed
>> devices. For high speed devices, it will slower the enumeration speed.
>> So in this patch we try the "old" enumeration scheme first for high
>> speed devices, and this is what Windows does since Windows 8.
>>
>> Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
>> ---
>> Changes in v2:
>> 1. As suggested by Alan, mention in the commit log that this change is
>> follow what the Window does.
>> 2. As suggested by Roger, update the kernel-parameter description.
>> ---
>>  Documentation/admin-guide/kernel-parameters.txt | 3 ++-
>>  drivers/usb/core/hub.c                          | 5 ++++-
>>  2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt
>> b/Documentation/admin-guide/kernel-parameters.txt
>> index 533ff5c..95db23c 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -4453,7 +4453,8 @@
>>
>>  	usbcore.old_scheme_first=
>>  			[USB] Start with the old device initialization
>> -			scheme (default 0 = off).
>> +			scheme,  applies only to low and full-speed devices
>> +			 (default 0 = off).
>>
>>  	usbcore.usbfs_memory_mb=
>>  			[USB] Memory limit (in MB) for buffers allocated by diff --git
>> a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index
>> 1fb2668..d265b19 100644
>> --- a/drivers/usb/core/hub.c
>> +++ b/drivers/usb/core/hub.c
>> @@ -2661,10 +2661,13 @@ static bool use_new_scheme(struct
>usb_device *udev, int retry,
>>  	int old_scheme_first_port =
>>  		port_dev->quirks & USB_PORT_QUIRK_OLD_SCHEME;
>>
>> +	int quick_enumeration = (udev->speed == USB_SPEED_HIGH);
>
Okey, will fix in v3

>Minor style point: the preceding blank line should be eliminated.
>
>> +
>>  	if (udev->speed >= USB_SPEED_SUPER)
>>  		return false;
>>
>> -	return USE_NEW_SCHEME(retry, old_scheme_first_port ||
>old_scheme_first);
>> +	return USE_NEW_SCHEME(retry, old_scheme_first_port ||
>old_scheme_first
>> +			      || quick_enumeration);
>>  }
>>
>>  /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
>
>Aside from that:
>
>Acked-by: Alan Stern <stern@rowland.harvard.edu>

Okay , tag will be applied in v3.