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RE: CPU Frequency change using PLL

To: "Linux MIPS" <linux-mips@linux-mips.org>
Subject: RE: CPU Frequency change using PLL
From: "Nori, Soma Sekhar" <nsekhar@ti.com>
Date: Tue, 28 Feb 2006 17:53:40 +0530
Cc: "Bharathi Subramanian" <sbharathi@MidasComm.Com>
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
Thread-index: AcY8YKsw15wz/xcaSeCe2rPrjX1O4gAAFfSg
Thread-topic: CPU Frequency change using PLL
> During my try, after changing the PLL Freq, the board is stops
> running. I feel, it is due to change in SDRAM Refresh rate. Is it
> right ?? Any body tried this, Kindly share exprience with me. Like how
> to reprogram the peripherals with-out affecting the operation etc..

Changing the PLL feeding only to the MIPS should not freeze the board.
You are
likely messing with PLL which feeds the peripherals as well. Peripherals
like
UART calculate the baud-rate dividers based on the input frequency. If
that 
changes, the peripheral should be re-initialized.

Changing the PLL which feeds the SDRAM will also likely cause memory
corruption.
Try putting the SDRAM in self-refresh for the duration of PLL
stablization and
then re-program the SDRAM refresh rate.

Thanks,
Sekhar Nori.

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