From mboxrd@z Thu Jan  1 00:00:00 1970
From: Felix Radensky <felix@embedded-sol.com>
Date: Thu, 28 May 2009 23:20:26 +0300
Subject: [U-Boot] Incorrect MDIO clock setup in 4xx network driver
Message-ID: <4A1EF20A.5040807@embedded-sol.com>
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To: u-boot@lists.denx.de

Hi,

The following piece of code in ppc_4xx_eth_init() results in incorrect MDIO
clock setup on Canyonlands, in the case when OPB clock is 100Mhz

    /* Whack the M1 register */
    mode_reg = 0x0;
    mode_reg &= ~0x00000038;
    if (sysinfo.freqOPB <= 50000000);
    else if (sysinfo.freqOPB <= 66666667)
        mode_reg |= EMAC_M1_OBCI_66;
    else if (sysinfo.freqOPB <= 83333333)
        mode_reg |= EMAC_M1_OBCI_83;
    else if (sysinfo.freqOPB <= 100000000)
        mode_reg |= EMAC_M1_OBCI_100;
    else
        mode_reg |= EMAC_M1_OBCI_GT100;

   out_be32((void *)EMAC_M1 + hw_p->hw_addr, mode_reg);

When OPB clock runs at 100Mhz, the value of sysinfo.freqOPB is 100000001,
so this code configures MDC clock to 3.3Mhz instead of less than 2.5Hz. This
is not a problem on Canyonlands, where Marvell PHY MDIO clock can run at
8.3Mhz. However other PHYs may actually require MDIO clock to be less than
2.5Mhz.

How about rewriting this code as

    freq = sysinfo.freqOPB / 1000000;
    if (freq <= 50)
    else if (freq <= 66)
       mode_reg |= EMAC_M1_OBCI_66;
    else if (freq <= 83)
       mode_reg |= EMAC_M1_OBCI_83;
    else if (freq <= 100)
       mode_reg |= EMAC_M1_OBCI_100;
    else
        mode_reg |= EMAC_M1_OBCI_GT100;

Felix.