Re: pch_uart and pch_phub clock selection

Tomoya MORINAGA
2012-02-17T09:50:34Z

Hi

2012年2月17日16:28 Feng Tang <feng.tang@intel.com>:
> I see that the the CM-iTC board is special-cased to set a 192MHz uart_clock.
> This is done in pch_uart.c code, but there is some register manipulation done in
> the pch_phub.c driver and I don't understand the connection. How are the two
> related?
According to your use, need to configure clock registers which are in pch_phub .
Upstreamed version, UART_CLK can be used directly(neither multiple nor
division) as UART clock.

You can get clock configuration information from SourceForge.
(http://sourceforge.net/projects/ml7213/files/Kernel%202.6.37/Release/Ver1.2.0/EG20TPCH_ML7213_ML7223_ML7831_linux-2.6.37_v120_20110930.tar.bz2/
and extract pch_phub. you can find readme.)
I extract it and show below.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<Configuration>
=======================

1. Over 115K baud rate UART settings
By default, UART can communicate less than 115Kbps.
In case you want UART to work more than 115Kbps, the following
clock configuration is necessary.
- Clock setting
Set BAUDSEL = usb_48mhz
Set PLL2VCO = "x 8" the clock
Set BAUDDIV = "x 1/6" the clock
Set UARTCLKSEL = PLL2 output
For details, please refer to ML7213/ML7223 EDS "5 Chip Configuration"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In case we want UART to work high baud rate(e.g.4Mbps), we set like above.
and execute "setserial /dev/ttyPCH0 baud_base 4000000".
I can see PCH_UART with 4Mbps works well.

Darren, is this answer for your question ?

> Tomoya, do you know if we can also set it to 192MHz for ML7223 IOH Bus-m/n?
Yes, you can.

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ROHM Co., Ltd.
tomoya