netdev - Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source.

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Message-ID: <4E3FDF01.1060708@pengutronix.de>
Date:	Mon, 08 Aug 2011 15:05:05 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Robin Holt <holt@....com>
CC:	Wolfgang Grandegger <wg@...ndegger.com>,
	U Bhaskar-B22300 <B22300@...escale.com>,
	socketcan-core@...ts.berlios.de, netdev@...r.kernel.org
Subject: Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source.

On 08/08/2011 01:31 PM, Robin Holt wrote:
> OK.  Dug a bit more.  The p1010 built-in clocksource seems to be the
> periphereal clock frequency which is system bus frequency divided
> by 2.  The clock source can not be changed, but the clock divider can

On arm the clock source is selected by bit 13 of CTRL:

> This bit selects the clock source to the CAN protocol interface (CPI)
> to be either the peripheral clock (driven by the PLL) or the crystal
> oscillator clock. The selected clock is the one fed to the prescaler
> to generate the SCLK (SCLK). In order to guarantee reliable
> operation, this bit must only be changed while the module is in
> disable mode. See Section 24.4.8.4, “Protocol Timing,” for more
> information.

> 0 The CAN engine clock source is the oscillator clock (24.576 MHz)
> 1 The CAN engine clock source is the bus clock (66.5 MHz)

cheers, Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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