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[PATCH] serial: samsung: move clock deactivation below uart registration

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Heiko Stübner

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Dec 4, 2013, 7:00:02 PM12/4/13
to
Commit 60e93575476f (serial: samsung: enable clock before clearing pending
interrupts during init) added handling of the controller clock during init.

On most systems this clock is also one of the baud_clock sources and
possibly used by the earlycon and thus already enabled by the bootloader.

Therefore a gap exists between s3c24xx_serial_init_port disabling the
clock and an attached console reenabling it, making the transition from
earlycon to regular console possibly hang the system - as seen on my
S3C2442 based Freerunner today.

Therefore move the disabling of the clock from s3c24xx_serial_init_port
below the uart port registration, effectively creating an overlap and
keeping the clock running non-stop if the console wants to grab this port.

Signed-off-by: Heiko Stuebner <he...@sntech.de>
---
drivers/tty/serial/samsung.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index c1af04d..9cd706d 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1209,7 +1209,6 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,

/* reset the fifos (and setup the uart) */
s3c24xx_serial_resetport(port, cfg);
- clk_disable_unprepare(ourport->clk);
return 0;
}

@@ -1287,6 +1286,13 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
platform_set_drvdata(pdev, &ourport->port);

+ /*
+ * Deactivate the clock enabled in s3c24xx_serial_init_port here,
+ * so that a potential re-enablement through the pm-callback overlaps
+ * and keeps the clock enabled in this case.
+ */
+ clk_disable_unprepare(ourport->clk);
+
#ifdef CONFIG_SAMSUNG_CLOCK
ret = device_create_file(&pdev->dev, &dev_attr_clock_source);
if (ret < 0)
--
1.7.10.4

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Tomasz Figa

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Dec 10, 2013, 9:00:01 AM12/10/13
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Hi Heiko,

On Thursday 05 of December 2013 00:54:38 Heiko St�bner wrote:
> Commit 60e93575476f (serial: samsung: enable clock before clearing pending
> interrupts during init) added handling of the controller clock during init.
>
> On most systems this clock is also one of the baud_clock sources and
> possibly used by the earlycon and thus already enabled by the bootloader.
>
> Therefore a gap exists between s3c24xx_serial_init_port disabling the
> clock and an attached console reenabling it, making the transition from
> earlycon to regular console possibly hang the system - as seen on my
> S3C2442 based Freerunner today.
>
> Therefore move the disabling of the clock from s3c24xx_serial_init_port
> below the uart port registration, effectively creating an overlap and
> keeping the clock running non-stop if the console wants to grab this port.
>
> Signed-off-by: Heiko Stuebner <he...@sntech.de>
> ---
> drivers/tty/serial/samsung.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)

Makes sense.

Reviewed-by: Tomasz Figa <t.f...@samsung.com>

Best regards,
Tomasz

Heiko Stübner

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Jan 21, 2014, 10:00:02 AM1/21/14
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Hi Greg,

just wanted to ask about the state of this patch. I can see it in your branch
named "fixes" [0] but it seems it hasn't made its way into the kernel neither
during the 3.13-rcs or with your 3.14-pull [1].


Thanks
Heiko


[0] https://git.kernel.org/cgit/linux/kernel/git/gregkh/tty.git/log/?h=fixes
[1]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bcee63488ece9a0fca8be19951428a7b41001e66

Greg Kroah-Hartman

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Jan 21, 2014, 12:30:01 PM1/21/14
to
On Tue, Jan 21, 2014 at 03:26:42PM +0100, Heiko Stübner wrote:
> Hi Greg,
>
> just wanted to ask about the state of this patch. I can see it in your branch
> named "fixes" [0] but it seems it hasn't made its way into the kernel neither
> during the 3.13-rcs or with your 3.14-pull [1].
>
>
> Thanks
> Heiko
>
>
> [0] https://git.kernel.org/cgit/linux/kernel/git/gregkh/tty.git/log/?h=fixes
> [1]
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bcee63488ece9a0fca8be19951428a7b41001e66

Ah crap, I missed this, sorry, I'll get it to Linus in time for
3.14-final, sorry about that.

greg k-h
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