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

Path	csiph.com!weretis.net!feeder4.news.weretis.net!news.mixmin.net!aioe.org!bofh.it!news.nic.it!robomod
From	gpramod@codeaurora.org
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] tty: msm_serial: remove static clk rate setting in probe
Date	Wed, 20 Apr 2016 08:10:02 +0200
Message-ID	<rpTuN-3ce-9@gated-at.bofh.it> (permalink)
References	<r9Tp7-5aA-1@gated-at.bofh.it>
X-Original-To	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
MIME-Version	1.0
Content-Type	text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding	8bit
X-Sender	gpramod@codeaurora.org
User-Agent	Roundcube Webmail/1.1.4
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	66
Organization	linux.* mail to news gateway
X-Original-Cc	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-serial@vger.kernel.org, Andy Gross <andy.gross@linaro.org>, David Brown <david.brown@linaro.org>, Jiri Slaby <jslaby@suse.com>, linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-owner@vger.kernel.org
X-Original-Date	Wed, 20 Apr 2016 11:36:00 +0530
X-Original-Message-ID	<1d51e468662254075fe2a8477f7addad@codeaurora.org>
X-Original-References	<1457318800-26090-1-git-send-email-srinivas.kandagatla@linaro.org>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1383062

Show key headers only | View raw

On 2016-03-07 08:16, 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@codeaurora.org>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---

Tested on DB410C. Fixed below curruption with earlycon:

[    0.815843] msm_iommu_ctx 1e3b000.qcom,iommu-ctx: context periph_SDC2 
using bank 27
����[    1.411080] console [ttyMSM0] enabled
[    1.411080] console [ttyMSM0] enabled

Tested-by: Pramod Gurav <gpramod@codeaurora.org>

> 
> Changes since v1:
> 	- removed empty line suggested by Greg KH
> 	- added reviewed-by
> 	- added extra comment suggested by Stephen Boyd.
> 
>  drivers/tty/serial/msm_serial.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/msm_serial.c 
> b/drivers/tty/serial/msm_serial.c
> index dcde955..3bf41ab 100644
> --- a/drivers/tty/serial/msm_serial.c
> +++ b/drivers/tty/serial/msm_serial.c
> @@ -1579,8 +1579,6 @@ static int msm_serial_probe(struct 
> platform_device *pdev)
>  		msm_port->pclk = devm_clk_get(&pdev->dev, "iface");
>  		if (IS_ERR(msm_port->pclk))
>  			return PTR_ERR(msm_port->pclk);
> -
> -		clk_set_rate(msm_port->clk, 1843200);
>  	}
> 
>  	port->uartclk = clk_get_rate(msm_port->clk);

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

Re: [PATCH v2] tty: msm_serial: remove static clk rate setting in  probe gpramod@codeaurora.org - 2016-04-20 08:10 +0200

csiph-web