[U-Boot] [PATCH] Move ICS CLK chip frequenty calculation code into a common board library

[Timur Tabi]

On Fri, May 21, 2010 at 1:59 PM, Timur Tabi <timur.tabi at gmail.com> wrote:

> Is this rounding algorithm the reason why I get output like this:
>
> Clock Configuration:
>       CPU0:799.992 MHz, CPU1:799.992 MHz,
>       CCB:399.996 MHz,
>       DDR:299.997 MHz (599.994 MT/s data rate) (Asynchronous), LBC:25
>  MHz
>
> If so, maybe we should fix it?

To answer my own question: yes.

So here's a better version of that function that rounds to the nearest
MHz and is of a proper coding style:

static const unsigned long ics307_clk_freq(unsigned char cw0, unsigned char cw1,
					   unsigned char cw2)
{
	static const u8 s2od[] = {
		10, 2, 8, 4, 5, 7, 3, 6
	};
	unsigned long vdw = (cw1 << 1) | (cw2 >> 7);
	unsigned long rdw = cw2 & 0x7f;
	unsigned long od = s2od[cw0 & 0x7];
	unsigned long freq;

	freq = 2 * CONFIG_ICS307_REFCLK_HZ * (vdw + 8) / ((rdw + 2) * od);

        /* Round freq to the nearest MHz */
	freq += 500000;
	freq /= 1000000;
	freq *= 1000000;

	debug("ICS307: CW[0-2]: %02X %02X %02X => %lu Hz\n", cw0, cw1, cw2,
			freq);
	return freq;
}

And the result:

Clock Configuration:
       CPU0:800  MHz, CPU1:800  MHz,
       CCB:400  MHz,
       DDR:300  MHz (600 MT/s data rate) (Asynchronous), LBC:25   MHz

-- 
Timur Tabi
Linux kernel developer at Freescale