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usb: core: reduce power-on-good delay time of root hub
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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

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1618017645-12259-1-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Chunfeng Yun authored and Greg Kroah-Hartman committed Apr 10, 2021
1 parent 26b7595 commit 90d28fb
Showing 1 changed file with 4 additions and 2 deletions.
6 changes: 4 additions & 2 deletions drivers/usb/core/hub.h
Original file line number Diff line number Diff line change
Expand Up @@ -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,
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