base baud reporting strange on efm32

base baud reporting strange on efm32

[Uwe Kleine-König]

Hello Kees, hello Greg,

since commit 
	7d12b97 (serial: report base_baud after initialization)
my efm32 machine says during startup:
	4000e400.uart: ttyefm4 at MMIO 0x4000e400 (irq = 25, base_baud = 0) is a efm32-uart

Is this "= 0" expected or is there something wrong in the driver?

(Sorry for not replying to the patch, but I didn't find it neither on
lkml nor on linux-serial.)

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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Re: base baud reporting strange on efm32

[Greg Kroah-Hartman]

On Mon, Oct 07, 2013 at 09:03:06AM +0200, Uwe Kleine-König wrote:
> Hello Kees, hello Greg,
> 
> since commit 
> 	7d12b97 (serial: report base_baud after initialization)
> my efm32 machine says during startup:
> 	4000e400.uart: ttyefm4 at MMIO 0x4000e400 (irq = 25, base_baud = 0) is a efm32-uart
> 
> Is this "= 0" expected or is there something wrong in the driver?

Does the hardware work properly?  That's the best test of this, right?

thanks,

greg k-h
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Re: base baud reporting strange on efm32

[Uwe Kleine-König]

On Mon, Oct 07, 2013 at 12:21:49AM -0700, Greg Kroah-Hartman wrote:
> On Mon, Oct 07, 2013 at 09:03:06AM +0200, Uwe Kleine-König wrote:
> > Hello Kees, hello Greg,
> > 
> > since commit 
> > 	7d12b97 (serial: report base_baud after initialization)
> > my efm32 machine says during startup:
> > 	4000e400.uart: ttyefm4 at MMIO 0x4000e400 (irq = 25, base_baud = 0) is a efm32-uart
> > 
> > Is this "= 0" expected or is there something wrong in the driver?
> 
> Does the hardware work properly?  That's the best test of this, right?
Yes, it works fine. Still I wonder if there is a problem that the driver
doesn't fill in port.uartclk early enough. In the efm32-uart driver (i.e.
drivers/tty/serial/efm32-uart.c) this member is only assigned to in
.startup.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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Re: base baud reporting strange on efm32

[Kees Cook]

On Mon, Oct 7, 2013 at 12:28 AM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> On Mon, Oct 07, 2013 at 12:21:49AM -0700, Greg Kroah-Hartman wrote:
>> On Mon, Oct 07, 2013 at 09:03:06AM +0200, Uwe Kleine-König wrote:
>> > Hello Kees, hello Greg,
>> >
>> > since commit
>> >     7d12b97 (serial: report base_baud after initialization)
>> > my efm32 machine says during startup:
>> >     4000e400.uart: ttyefm4 at MMIO 0x4000e400 (irq = 25, base_baud = 0) is a efm32-uart
>> >
>> > Is this "= 0" expected or is there something wrong in the driver?
>>
>> Does the hardware work properly?  That's the best test of this, right?
> Yes, it works fine. Still I wonder if there is a problem that the driver
> doesn't fill in port.uartclk early enough. In the efm32-uart driver (i.e.
> drivers/tty/serial/efm32-uart.c) this member is only assigned to in
> .startup.

Hm, yeah, it looks like uart_add_one_port() (which ultimately makes
the printk call) is called in efm32_uart_probe(), but uartclk gets set
during serial open (via efm32_uart_startup()).

So, it seems this "0" report is harmless. If the efm32 driver wants to
have something meaningful there, I guess the clk code needs to move
around.

-Kees

-- 
Kees Cook
Chrome OS Security
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