From: Roger Quadros <rogerq@ti.com>
To: Zeng Tao <prime.zeng@hisilicon.com>, <gregkh@linuxfoundation.org>,
<stern@rowland.harvard.edu>, <mathias.nyman@linux.intel.com>,
<drinkcat@chromium.org>, <felipe.balbi@linux.intel.com>,
<drake@endlessm.com>, <mike.looijmans@topic.nl>,
<joe@perches.com>
Cc: <linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] usb: hub: try old enumeration scheme first for high speed devices
Date: Fri, 10 Aug 2018 13:50:43 +0300 [thread overview]
Message-ID: <a29afa26-22b4-3188-f9ee-993e44df7703@ti.com> (raw)
In-Reply-To: <1533913304-15737-1-git-send-email-prime.zeng@hisilicon.com>
Hi,
On 10/08/18 18:01, 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.
How slow does it get? Is it significant?
Do we risk breaking existing HS devices that work? I don't think we can
be sure till we run this through testing.
>
> Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
> ---
> drivers/usb/core/hub.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> 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;
how about replacing the above if with
if (udev->speed >= USB_SPEED_HIGH)
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);
> }
Now we no longer respect the "old_scheme_first" parameter for most of the devices.
It should be clarified in Documentation/admin/kernel-parameters.txt that
"old_scheme_first" is only applicable to LOW/FULL speed devices.
>
> /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
>
--
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next prev parent reply other threads:[~2018-08-10 10:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-10 15:01 [PATCH] usb: hub: try old enumeration scheme first for high speed devices Zeng Tao
2018-08-10 10:50 ` Roger Quadros [this message]
2018-08-10 14:19 ` Alan Stern
2018-08-14 7:35 ` Zengtao (B)
2018-08-14 14:39 ` Alan Stern
2018-08-16 6:21 ` Zengtao (B)
2018-08-16 7:16 ` Roger Quadros
2018-08-16 10:59 ` Zengtao (B)
2018-08-16 11:13 ` Roger Quadros
2018-08-17 2:15 ` Zengtao (B)
2018-08-14 7:33 ` Zengtao (B)
2018-08-16 7:31 ` Roger Quadros
2018-09-28 11:27 Zeng Tao
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