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From: Sebastian Andrzej Siewior <email@example.com>
To: Jeaho Hwang <firstname.lastname@example.org>
Cc: "Peter Chen" <email@example.com>,
"Greg Kroah-Hartman" <firstname.lastname@example.org>,
"Thomas Gleixner" <email@example.com>,
"Linux team" <firstname.lastname@example.org>,
"변무광(Byeon Moo Kwang)/자동화연)Automation Platform연구팀"
"최기홍(Choi Ki Hong)/자동화연)Automation Platform연구팀"
Subject: Re: [PATCH v2] usb: chipidea: local_irq_save/restore added for hw_ep_prime
Date: Thu, 19 Aug 2021 10:47:59 +0200 [thread overview]
Message-ID: <email@example.com> (raw)
On 2021-08-19 08:50:27 [+0900], Jeaho Hwang wrote:
> Without RT, udc_irq runs as a forced threaded irq handler, so it runs
> without any interruption or preemption. NO similar case is found on
I see only a devm_request_irq() so no force-threading here. Booting with
threadirqs would not lead to the problem since commit
81e2073c175b8 ("genirq: Disable interrupts for force threaded handlers")
> > If this function here is sensitive to timing (say the cpu_relax() loop
> > gets interrupt for 1ms) then it has to be documented as such.
> The controller sets ENDPTSETUPSTAT register if the host sent a setup packet.
> yes it is a timing problem. I will document that and resubmit again if
> you agree that local_irq_save could help from the timing problem.
> Thanks for the advice.
If it is really a timing issue in the function as you describe below
then disabling interrupts would help and it is indeed an RT only issue.
So you read OP_ENDPTSETUPSTAT, it is 0, all good.
You write OP_ENDPTPRIME, wait for it to be cleared.
Then you read OP_ENDPTSETUPSTAT again and if it is 0, all good.
And the TWD interrupt could delay say the second read would read 1 and
it is invalidated. Which looks odd.
However, it is "okay" if the TWD interrupt happens after the second
read? Even if the host sends a setup packet, nothing breaks?
Do you have numbers on how long irq-off section is here? It seems to
depend on how long the HW needs to clear the OP_ENDPTPRIME bits.
next prev parent reply other threads:[~2021-08-19 8:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-17 9:53 Jeaho Hwang
2021-08-18 16:17 ` Sebastian Andrzej Siewior
2021-08-18 23:50 ` Jeaho Hwang
2021-08-19 8:47 ` Sebastian Andrzej Siewior [this message]
2021-08-20 5:15 ` Jeaho Hwang
2021-08-21 5:05 ` Peter Chen
2021-08-21 7:04 ` Jeaho Hwang
2021-08-23 16:14 ` Sebastian Andrzej Siewior
2021-08-23 16:51 ` Sebastian Andrzej Siewior
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