usb: hub: Add quirk to decrease IN-ep poll interval for Microchip USB491x hub

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There is a potential delay in notifying Linux USB drivers of downstream
USB bus activity when connecting a high-speed or superSpeed device via the
Microchip USB491x hub. This delay is due to the fixed bInterval value of
12 in the silicon of the Microchip USB491x hub.

Microchip requested to ignore the device descriptor and decrease that
value to 9 as it was too late to modify that in silicon.

This patch speeds up the USB enummeration process that helps to pass
Apple Carplay certifications and improve the User experience when utilizing
the USB device via Microchip Multihost USB491x Hub.

A new hub quirk HUB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL speeds up
the notification process for Microchip USB491x hub by limiting
the maximum bInterval value to 9.

Signed-off-by: Hardik Gajjar <hgajjar@de.adit-jv.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20231205181829.127353-2-hgajjar@de.adit-jv.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Hardik Gajjar 2023-12-05 19:18:29 +01:00 • committed by Greg Kroah-Hartman

parent 6666ea93d2

commit 855d75cf83

1 changed files with 29 additions and 0 deletions

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drivers/usb/core/hub.c

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