linux-kernel - Re: [PATCH v2] tty: serial: msm: Don't reconfigure same baud rate

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Date:	Tue, 21 Jun 2016 12:43:39 +0300
From:	Nicolas Dechesne <nicolas.dechesne@...aro.org>
To:	Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:	Andy Gross <andy.gross@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	David Brown <david.brown@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	linux-soc@...r.kernel.org, linux-serial@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tty: serial: msm: Don't reconfigure same baud rate

On Fri, Jun 17, 2016 at 1:02 PM, Nicolas Dechesne
<nicolas.dechesne@...aro.org> wrote:
> <bjorn.andersson@...aro.org> wrote:
>> msm_set_termios() is called whenever the tty is opened. Setting the baud
>> rate requires a full reset of the msm serial block, even when the rate
>> is unchanged. In the case when the same uart is used as console this
>> reset will discard any console output data still being clocked out of
>> the TX fifo.
>>
>> By skipping the rate-change in the case where the baud rate is unchanged
>> since last request we can avoid the reset and the discarding of the
>> data.
>>
>> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>
>
> Tested-by: Nicolas Dechesne <nicolas.dechesne@...aro.org>
>
> I no longer see this type of corruption on serial console
>
> [    6.325118] ALSA device �[    6.333338] Freeing unused kernel
> memory: 572K (ffffffc000c10000 - ffffffc000c9f000)
> [   13.800269]  remoteproc2: remote processor a20400�[  OK  ] Started
> Start the WCN core.
> [ �         Starting Update UTMP about System Runlevel Changes...


oops. today i tried on APQ8064 boards , both IFC6410Plus and SD
600eval, and I can no longer 'type' into the serial console, I can get
debug messages though. Reverting this change 'fixes' the problem.