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SubjectRe: [PATCH] pch_uart: Change default UART clock setting 192MHz
On 02/21/2012 03:43 PM, Tomoya MORINAGA wrote:
> 2012年2月22日1:07 Darren Hart <>:
>> When does the phub driver update the clock registers?
> I've already posted pch_phub patch for 192MHz setting.
> You can see the patch form below.

Yes, I applied the patch. The problem seems to be this:

DVHART: parse_options (8250_early.c)
DVHART: pch_console_setup
DVHART: pch_console_setup
DVHART: pch_phub_probe: set CLKCFG UART to 192MHz

As you can see, the pch_phub_probe happens much too late.

I can get it to work with a boot command line like this:
earlycon=uart8250,io,0x2050,115200n8 console=ttyPCH1,115200n8

And hacking all the BASE_BAUD references to be 48000000
(my current hardware sets the clock to 48MHz in firmware).
This gets things working until pch_phub gets around to setting
the CLKCFG register for the UART clock.

I'd prefer to not have to use the earlycon parameter/code,
but we need a way for the pch_uart to understand the difference
between early boot and post-phub setup. Can we read the CLKCFG
register in pch_console_setup to dynamically configure the
port->uartclk? (not sure that's even the right place to do it).


>>> Signed-off-by: Tomoya MORINAGA <>
>>> ---
>>> Related patch is
> ---
> ROHM Co., Ltd.
> tomoya

Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

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