linux-kernel - Re: [PATCH v5 0/3] Fix UART DMA freezes for i.MX SOCs

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Date:   Mon, 23 Sep 2019 17:09:35 +0200
From:   Jan Lübbe <jlu@...gutronix.de>
To:     Philipp Puschmann <philipp.puschmann@...ix.com>,
        Adam Ford <aford173@...il.com>
Cc:     fugang.duan@....com, Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        vkoul@...nel.org, NXP Linux Team <linux-imx@....com>,
        Sascha Hauer <kernel@...gutronix.de>,
        dmaengine@...r.kernel.org, dan.j.williams@...el.com,
        Robin Gong <yibin.gong@....com>,
        Fabio Estevam <festevam@...il.com>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH v5 0/3] Fix UART DMA freezes for i.MX SOCs

On Mon, 2019-09-23 at 17:06 +0200, Philipp Puschmann wrote:
> Thanks for testing.
> With my local setup i still have very few tx timeouts too. But i think they have a different
> cause and especially different consequences. When the problem addressed by this series
> appear you get a whole bunch of tx timeouts (and maybe errors from Bluetooth
> layer) and monitoring received Bluetooth packets with hciconfig shows a
> complete freeze of rx counter. Only resetting the hci_uart driver and the wl1837mon then helps.
> With these patches applied the rx data shold still coming in even if a single or
> multiple tx timeout error happen. I'm not sure where the error comes from and what the
> consequences for the Bluetooth layer are.

For testing, I've used a UART connected to my development host and
configured *mismatching* baud rates. Sending /dev/urandom from the host
to the i.MX6 then triggered the DMA hang (because each character
triggers and error indication, which "uses" a full buffer).

Regards,
Jan
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