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

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Date:	Sat, 5 Mar 2016 14:26:59 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	Andy Gross <andy.gross@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	David Brown <david.brown@...aro.org>,
	Jiri Slaby <jslaby@...e.com>, linux-arm-msm@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: msm_serial: remove static clk rate setting in probe

On Tue, Mar 01, 2016 at 11:22:53AM +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 ateast not required with the mainline driver.
> 
> 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
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  drivers/tty/serial/msm_serial.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
> index dcde955..0a31b3e 100644
> --- a/drivers/tty/serial/msm_serial.c
> +++ b/drivers/tty/serial/msm_serial.c
> @@ -1580,7 +1580,6 @@ static int msm_serial_probe(struct platform_device *pdev)
>  		if (IS_ERR(msm_port->pclk))
>  			return PTR_ERR(msm_port->pclk);
>  
> -		clk_set_rate(msm_port->clk, 1843200);

Delete the unneeded blank line as well please, when you resend this.

thanks,

greg k-h