From: Alan Stern <stern@rowland.harvard.edu>
To: Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
Nishad Kamdar <nishadkamdar@gmail.com>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org,
Eddie Hung <eddie.hung@mediatek.com>
Subject: Re: [RFC PATCH] usb: core: reduce power-on-good delay time of root hub
Date: Fri, 9 Apr 2021 11:09:11 -0400 [thread overview]
Message-ID: <20210409150911.GC1333284@rowland.harvard.edu> (raw)
In-Reply-To: <1617935947-24045-1-git-send-email-chunfeng.yun@mediatek.com>
On Fri, Apr 09, 2021 at 10:39:07AM +0800, Chunfeng Yun wrote:
> Return the exactly delay time given by root hub descriptor,
> this helps to reduce resume time etc.
>
> Due to the root hub descriptor is usually provided by the host
> controller driver, if there is compatibility for a root hub,
> we can fix it easily without affect other root hub
>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
> ---
> drivers/usb/core/hub.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
> index 73f4482d833a..22ea1f4f2d66 100644
> --- a/drivers/usb/core/hub.h
> +++ b/drivers/usb/core/hub.h
> @@ -148,8 +148,10 @@ static inline unsigned hub_power_on_good_delay(struct usb_hub *hub)
> {
> unsigned delay = hub->descriptor->bPwrOn2PwrGood * 2;
>
> - /* Wait at least 100 msec for power to become stable */
> - return max(delay, 100U);
> + if (!hub->hdev->parent) /* root hub */
> + return delay;
> + else /* Wait at least 100 msec for power to become stable */
> + return max(delay, 100U);
> }
>
> static inline int hub_port_debounce_be_connected(struct usb_hub *hub,
> --
> 2.18.0
>
prev parent reply other threads:[~2021-04-09 15:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-09 2:39 [RFC PATCH] usb: core: reduce power-on-good delay time of root hub Chunfeng Yun
2021-04-09 15:09 ` Alan Stern [this message]
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