serial: core: Fix runtime PM handling for pending tx

stable inclusion
from stable-v6.6.1
commit f1125301091a2bbdca0562fdc70a2482c8fcca24
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8IKRU

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1125301091a2bbdca0562fdc70a2482c8fcca24



--------------------------------

commit 6f699743aebf07538e506a46c5965eb8bdd2c716 upstream.

Richard reported that a serial port may end up sometimes with tx data
pending in the buffer for long periods of time.

Turns out we bail out early on any errors from pm_runtime_get(),
including -EINPROGRESS. To fix the issue, we need to ignore -EINPROGRESS
as we only care about the runtime PM usage count at this point. We check
for an active runtime PM state later on for tx.

Fixes: 84a9582f ("serial: core: Start managing serial controllers to enable runtime PM")
Cc: stable <stable@kernel.org>
Reported-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Bruce Ashfield <bruce.ashfield@gmail.com>
Cc: Mikko Rapeli <mikko.rapeli@linaro.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Randy MacLeod <randy.macleod@windriver.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Tested-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231023074856.61896-1-tony@atomide.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>