LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jeaho Hwang <jhhwang@rtst.co.kr>
To: Peter Chen <peter.chen@kernel.org>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Linux team" <team-linux@rtst.co.kr>,
	"변무광(Byeon Moo Kwang)/자동화연)Automation Platform연구팀"
	<mkbyeon@lselectric.co.kr>,
	"최기홍(Choi Ki Hong)/자동화연)Automation Platform연구팀"
	<khchoib@lselectric.co.kr>
Subject: Re: [PATCH v2] usb: chipidea: add loop timeout for hw_ep_set_halt()
Date: Fri, 27 Aug 2021 10:35:05 +0900	[thread overview]
Message-ID: <CAJk_X9i68vPWDEf2x6WtV73XRCuhyZF_26KtK=J+Z76ZyQe8PQ@mail.gmail.com> (raw)
In-Reply-To: <20210826230658.GB4335@Peter>

2021년 8월 27일 (금) 오전 8:08, Peter Chen <peter.chen@kernel.org>님이 작성:
>
> On 21-08-24 17:31:44, Jeaho Hwang wrote:
> > 2021년 8월 17일 (화) 오후 3:44, Jeaho Hwang <jhhwang@rtst.co.kr>님이 작성:
> > >
> > > If ctrl EP priming is failed (very rare case in standard linux),
> > > hw_ep_set_halt goes infinite loop. waiting 100 times was enough
> > > for zynq7000.
> > >
> >
> > Hi Peter.
> > I found from zynq7000 TRM that the hardware clears Stall bit if a
> > setup packet is received on a control endpoint.
> > I think hw_ep_set_halt goes infinite loop since:
> >
> > 1. hw_ep_prime for control EP which is called from
> > isr_tr_complete_handler -> isr_setup_status_phase is failed due to a
> > setup packet received.
>
> How do you know that? Do you observe the new setup packet on the bus
> before the current status stage? Usually, the host doesn't begin new setup
> transfer before current setup transfer has finished.
>
> Peter
>

I found an error return from the second ENDPTSETUPSTAT checking
routine, then setting the stall bit(TXS) kept failing. So I guessed it
is due to a setup packet received.
I didn't observe the setup packet by e.g. HW probes. Any other reason
to produce that symptom?

For reminder, only reproduced on preemp_rt kernel and with Windows(10)
RNDIS host.

thanks.

 191 static int hw_ep_prime(struct ci_hdrc *ci, int num, int dir, int is_ctrl)
 192 {
 193     int n = hw_ep_bit(num, dir);
 194
 195     /* Synchronize before ep prime */
 196     wmb();
 197
 198     if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num)))
 199         return -EAGAIN;
 200
 201     hw_write(ci, OP_ENDPTPRIME, ~0, BIT(n));
 202
 203     while (hw_read(ci, OP_ENDPTPRIME, BIT(n)))
 204         cpu_relax();
 205     if (is_ctrl && dir == RX && hw_read(ci, OP_ENDPTSETUPSTAT, BIT(num)))
 206         return -EAGAIN;
             ~~~~~~~~~~~~~~~~
 207
 208     /* status shoult be tested according with manual but it doesn't work */
 209     return 0;
 210 }

> > 2. in isr_tr_complete_handler it tries to call _ep_set_halt if either
> > isr_tr_complete_low or isr_setup_status_phase returns error.
> > 3. Since the control EP got a setup packet, HW resets TXS bit just as
> > the driver sets inside hw_ep_set_halt so it goes infinite loop.
> >
> > Does it make sense? If it is right, we shouldn't call _ep_set_halt if
> > the err is -EAGAIN, which could be returned ONLY due to the setup
> > packet issue described above.
> > And the loop timeout is not required anymore.
> >
> > Can I ask your opinion on this, Peter and USB experts?
> >
> > Thanks.
> >

  reply	other threads:[~2021-08-27  1:35 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-17  6:43 Jeaho Hwang
2021-08-24  8:31 ` Jeaho Hwang
2021-08-26 23:07   ` Peter Chen
2021-08-27  1:35     ` Jeaho Hwang [this message]
2021-08-28  1:38       ` Peter Chen
2021-08-28  3:10         ` Jeaho Hwang
2021-08-26 11:17 ` Greg Kroah-Hartman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAJk_X9i68vPWDEf2x6WtV73XRCuhyZF_26KtK=J+Z76ZyQe8PQ@mail.gmail.com' \
    --to=jhhwang@rtst.co.kr \
    --cc=gregkh@linuxfoundation.org \
    --cc=khchoib@lselectric.co.kr \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=mkbyeon@lselectric.co.kr \
    --cc=peter.chen@kernel.org \
    --cc=team-linux@rtst.co.kr \
    --subject='Re: [PATCH v2] usb: chipidea: add loop timeout for hw_ep_set_halt()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).