linux-kernel - Re: [PATCH] imx-serial: RX DMA startup latency

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Message-ID: <20170517100418.rvn2rajpvkpaf453@pengutronix.de>
Date:   Wed, 17 May 2017 12:04:18 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Peter Senna Tschudin <peter.senna@...labora.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] imx-serial: RX DMA startup latency

On Sun, May 14, 2017 at 02:35:15PM +0200, Peter Senna Tschudin wrote:
> 18a4208 introduced a change to reduce the RX DMA latency on the first reception
> when the serial port was opened for reading. However it was claiming a hardirq
> unsafe lock after a hardirq safe lock which is not allowed and causes lockdep
> to complain verbosely.
> 
> This patch changes the code to always start RX DMA earlier, instead of
> relying on the flags used to open the serial port removing the code that
> was looking for the serial file flags.
> 
> CC: Sascha Hauer <s.hauer@...gutronix.de>
> Signed-off-by: Peter Senna Tschudin <peter.senna@...labora.com>
> ---
> Tested on iMX53.

Tested-by: Sascha Hauer <s.hauer@...gutronix.de>

(on an i.MX6)

Sascha

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