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From: "Petr Štetiar" <ynezz@true.cz>
To: Vinod Koul <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org, Robin Gong <yibin.gong@nxp.com>,
	Fabio Estevam <festevam@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	Lucas Stach <l.stach@pengutronix.de>
Subject: Re: imx-uart DMA transaction error leading to OOPS on 4.14.95
Date: Mon, 11 Feb 2019 10:28:20 +0100
Message-ID: <20190211092820.GS26426@meh.true.cz> (raw)
In-Reply-To: <20190211120616.GT4296@vkoul-mobl>

Vinod Koul <vkoul@kernel.org> [2019-02-11 17:36:16]:

Hi,

> > I've just encountered following OOPS on 4.14.95:
> > 
> >   imx-uart 21f0000.serial: DMA transaction error.
> 
> Do you see this on mainline as well, bit of fixes went into this driver
> recently...

I've hit it only once on 4.14 so far, it's quite hard to reproduce it, so no
big deal, but I've just thought, that someone might be interested. Once I find
some way to reproduce it, I'll try to test it on some recent kernel.

BTW, any idea which of those fixes might be related to this Oops and might be
worth backporting to 4.14?

> >   Unable to handle kernel paging request at virtual address a0ee501a
> >   pgd = 9d7d4000
> >   [a0ee501a] *pgd=2d8d1811, *pte=00000000, *ppte=00000000
> >   Internal error: Oops: 7 [#1] SMP ARM
...
> >   CPU: 0 PID: 2536 Comm: sh Not tainted 4.14.95 #0
> >   Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> >   task: 9f67ca00 task.stack: 9b642000
> >   PC is at sdma_int_handler+0x7c/0x17c
> 
> So we get an interrupt while doing shutdown.. That is interesting..

I'm using serial console on ttymxc0 (115200,8n1) and UHF RFID reader on
ttymxc3(921600,8n1) which is sending reports asynchronously and it was active
during the shutdown as I was testing new hardware revision during that time.

> >   PC is at sdma_int_handler+0x7c/0x17c
> >   LR is at console_unlock+0x480/0x4ec

I'm not sure how to interpret this, but is it possible, that there might be
some race while sdma_int_handler could be processing interrupt on ttymxc3
while the system is doing some console output on ttymxc0? I just use the
console for observation, so I wasn't typing or otherwise utilizing it, so
probably no reason for interrupt from ttymxc0.

-- ynezz

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Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-06  8:13 Petr Štetiar
2019-02-11 12:06 ` Vinod Koul
2019-02-11  9:28   ` Petr Štetiar [this message]
2019-02-12  3:42     ` Robin Gong
2019-02-12  6:39       ` Robin Gong

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