[U-Boot] Incorrect MDIO clock setup in 4xx network driver

[Stefan Roese]

Hi Felix,

(btw, please cc me on 4xx related patches, otherwise I might miss them)

On Thursday 28 May 2009 22:20:26 Felix Radensky wrote:
> 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;

Looks good to me. Do you plan to send a patch for this?

Thanks.

Best regards,
Stefan

=====================================================================
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80  Email: office at denx.de
=====================================================================