From: Andrew Morton <akpm@linux-foundation.org>
To: "H. Nikolaus Schaller" <hns@goldelico.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>, Vignesh R <vigneshr@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andreas Kemnade <andreas@kemnade.info>,
Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Ian Campbell <ijc+devicetree@hellion.org.uk>,
Kumar Gala <galak@codeaurora.org>,
Jonathan Corbet <corbet@lwn.net>,
Tony Lindgren <tony@atomide.com>, NeilBrown <neilb@suse.de>,
Fabian Frederick <fabf@skynet.be>,
linux-kernel@vger.kernel.org, letux-kernel@openphoenux.org
Subject: Re: [PATCH] w1:omap_hdq: fix regression
Date: Mon, 18 Jul 2016 12:29:25 -0700 [thread overview]
Message-ID: <20160718122925.80d840e96ef9ae0b3e09a655@linux-foundation.org> (raw)
In-Reply-To: <9c4ed8a45c6c0f99c5fc41842c4781f37cf5d70a.1468858236.git.hns@goldelico.com>
On Mon, 18 Jul 2016 18:10:37 +0200 "H. Nikolaus Schaller" <hns@goldelico.com> wrote:
> commit <e93762bbf681> ("w1: masters: omap_hdq: add support for 1-wire mode")
> did add a statement to clear the hdq_irqstatus flags in hdq_read_byte().
>
> If the hdq reading process is scheduled slowly or interrupts are disabled
> for a while the hardware read activity might already be finished on entry
> of hdq_read_byte(). And hdq_isr() already has set the hdq_irqstatus to
> 0x6 (can be seen in debug mode) denoting that both, the TXCOMPLETE
> and RXCOMPLETE interrupts occurred in parallel.
>
> This means there is no need to wait and the hdq_read_byte() can just read
> the byte from the hdq controller.
>
> By resetting hdq_irqstatus to 0 the read process is forced to be always
> waiting again (because the if statement always succeeds) but the hardware
> will not issue another RXCOMPLETE interrupt. This results in a false
> timeout.
>
> After such a situation the hdq bus hangs.
>
> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Needs a cc:stable.
I'll assume Greg will be handling this patch.
prev parent reply other threads:[~2016-07-18 19:29 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-18 16:10 [PATCH] w1:omap_hdq: fix regression H. Nikolaus Schaller
2016-07-18 19:29 ` Andrew Morton [this message]
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=20160718122925.80d840e96ef9ae0b3e09a655@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=andreas@kemnade.info \
--cc=corbet@lwn.net \
--cc=fabf@skynet.be \
--cc=galak@codeaurora.org \
--cc=gregkh@linuxfoundation.org \
--cc=hns@goldelico.com \
--cc=ijc+devicetree@hellion.org.uk \
--cc=letux-kernel@openphoenux.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=neilb@suse.de \
--cc=pawel.moll@arm.com \
--cc=robh+dt@kernel.org \
--cc=tony@atomide.com \
--cc=vigneshr@ti.com \
--cc=zbr@ioremap.net \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).