usb: acpi: add helper to check port lpm capability using acpi _DSM

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commit cd702d18c8 upstream.

Add a helper to evaluate ACPI usb device specific method (_DSM) provided
in case the USB3 port shouldn't enter U1 and U2 link states.

This _DSM was added as port specific retimer configuration may lead to
exit latencies growing beyond U1/U2 exit limits, and OS needs a way to
find which ports can't support U1/U2 link power management states.

This _DSM is also used by windows:
Link: https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/usb-device-specific-method---dsm-

Some patch issues found in testing resolved by Ron Lee

Cc: stable@vger.kernel.org
Tested-by: Ron Lee <ron.lee@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20230116142216.1141605-7-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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This commit is contained in:

Mathias Nyman 2023-01-16 16:22:15 +02:00 • committed by Greg Kroah-Hartman

parent 8c36de0935

commit b7904d2015

2 changed files with 68 additions and 0 deletions

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65

drivers/usb/core/usb-acpi.c

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3

include/linux/usb.h

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