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

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Date:	Wed, 22 Jun 2016 10:59:04 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Nicolas Dechesne <nicolas.dechesne@...aro.org>,
	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 21/06/16 10:43, Nicolas Dechesne wrote:
> 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.

Am also hitting the same issue as Nico on IFC6410 with this patch.


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