Description based on one by Yasushi Asano:
According to 6.7.22 A-UUT “Device No Response” for connection timeout
of USB OTG and EH automated compliance plan v1.2, enumeration failure
has to be detected within 30 seconds. However, the old and new
enumeration schemes each make a total of 12 attempts, and each attempt
can take 5 seconds to time out, so the PET test fails.
This patch adds a new Kconfig option (CONFIG_USB_FEW_INIT_RETRIES);
when the option is set all the initialization retry loops except the
outermost are reduced to a single iteration. This reduces the total
number of attempts to four, allowing Linux hosts to pass the PET test.
The new option is disabled by default to preserve the existing
behavior. The reduced number of retries may fail to initialize a few
devices that currently do work, but for the most part there should be
no change. And in cases where the initialization does fail, it will
fail much more quickly.
Reported-and-tested-by: yasushi asano <yazzep@gmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20200928152217.GB134701@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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