linux-kernel - Re: [PATCH v2] tty: msm_serial: remove static clk rate setting in probe

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Date:	Mon, 18 Apr 2016 15:16:39 -0500
From:	Andy Gross <andy.gross@...aro.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-serial@...r.kernel.org, David Brown <david.brown@...aro.org>,
	Jiri Slaby <jslaby@...e.com>, linux-arm-msm@...r.kernel.org,
	linux-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tty: msm_serial: remove static clk rate setting in
 probe

On Mon, Mar 07, 2016 at 02:46:40AM +0000, Srinivas Kandagatla wrote:
> The issue with setting up a fixed clock rate at probe is that it would
> overwrite the console rate set by the bootloader for its console device.
> This would result in serial out corruption or missing log when we system
> is booted with earlycon. This is not a issue if we boot system without
> earlycon.
> 
> This setup is at least not required with the mainline driver, this code
> used to be required because the clk_enable() call would fail if
> clk_set_rate() wasn't called first.
> 
> Originally the issue was noticed on DB410c which is based on APQ8016
> chipset.
> 
> Without this patch the console log with earlycon would look like:
> ...
> [    0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=64, nr_cpu_ids=1
> [    0.000000] NR_IRQS:64 nr_irqs:64 0
> ����+HH��0.699378] console [ttyMSM0] enabled
> [    0.699378] console [ttyMSM0] enabled
> [    0.702003] bootconsole [uart0] disabled
> [    0.702003] bootconsole [uart0] disabled
> ...
> 
> with this patch I can see all the skipped lines on the console
> 
> Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>

Acked-by: Andy Gross <andy.gross@...aro.org>

Greg,

Can you pick this one up?

Thanks

Andy