linux-kernel - Re: [PATCH v2] usb: chipidea: local_irq_save/restore added for hw_ep

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Date:   Mon, 23 Aug 2021 18:51:02 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Jeaho Hwang <jhhwang@...t.co.kr>
Cc:     Peter Chen <peter.chen@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-rt-users@...r.kernel.org, Linux team <team-linux@...t.co.kr>,
        변무광(Byeon Moo Kwang)/자동화연)Automation Platform연구팀 
        <mkbyeon@...lectric.co.kr>,
        최기홍(Choi Ki Hong)/자동화연)Automation Platform연구팀 
        <khchoib@...lectric.co.kr>
Subject: Re: [PATCH v2] usb: chipidea: local_irq_save/restore added for
 hw_ep_prime

On 2021-08-20 14:15:55 [+0900], Jeaho Hwang wrote:
> So we protect irqs inside hw_ep_priming not to make error cases and
> also add a timeout inside the hw_ep_set_halt loop for a walkaround.
> The timeout patch is submitted to linux-usb.
> ( https://marc.info/?l=linux-usb&m=162918269024007&w=2 )
>
> We withdrew this patch since we don't know if disabling irq is the
> best solution to solve the problem and udc would work fine with
> hw_ep_set_halt walkaround even though hw_ep_prime fails.
> But we are still trying to find out the cause of this symptom so We'd
> so appreciate it if RT or USB experts share some ideas or ways to
> report somewhere. Xilinx doesn't provide any support without their
> official kernel :(

The UDC driver sometimes drops the lock and acquires it again. On UP it
would not matter but on SMP/RT the other may acquire lock and do
something with the HW. One thing that you could check if there is any HW
access in between which would affect the behaviour.

> Thanks for the discussion Sebastian.
> 
> Jeaho Hwang.

Sebastian