[Bugme-new] [Bug 4310] New: ppc 8260 fcc ethernet driver cannot read LXT971 PHY id

[Andrew Morton]

I'm not sure that we have a maintainer for fcc_enet.c.  Could you
please send in a tested diff?

bugme-daemon at osdl.org wrote:
>
> http://bugme.osdl.org/show_bug.cgi?id=4310
> 
>            Summary: ppc 8260 fcc ethernet driver cannot read LXT971 PHY id
>     Kernel Version: 2.6.10
>             Status: NEW
>           Severity: normal
>              Owner: platform_ppc-32 at kernel-bugs.osdl.org
>          Submitter: oray at lucent.com
> 
> 
> Distribution: www.kernel.org
> Hardware Environment: Target: PowerPC 8260 custom board
> Software Environment: Red Hat 9 cross development using ELDK 3.1 distribution.
> Problem Description: Fast ethernet driver (fcc_enet.c) initialization fails to
> read a valid id from registers 2 and 3 of the LXT971 PHY device and calls the
> panic routine. The bug is in the mii_send_receive() function. During the read
> phase, per LXT971 data sheet, the device starts driving the MDIO line after the
> rising edge of the MDC clock and it could take up to 150ns before the data
> settles. The driver reads the MDIO line before waiting for the data to settle
> down and thus reads in garbage. I fixed the problem by moving the sampling of
> the MDIO line to after the MDC clock is taken low. The code snippet follows:   
> 
> 
>                 for (i = 0, off = 15; i < 16; i++, off--)
>                 {
> #define FCC_8260_BUG
>                         FCC_PDATC_MDC(1);
>                         retval <<= 1;
> #ifndef FCC_8260_BUG
>                         if (io->iop_pdatc & fip->fc_mdio)
>                                 retval++;
>                         udelay(1);
>                         FCC_PDATC_MDC(0);
> #else
>                         udelay(1);
>                         FCC_PDATC_MDC(0);
>                         if (io->iop_pdatc & fip->fc_mdio)
>                                 retval++;
> #endif
>                         udelay(1);
> #undef FCC_8260_BUG
>                 }
> 
> 
> Steps to reproduce: Is likely to happen on an 8260 target with any kind of PHY,
> not just the LXT971, hooked up to the FCC port.
> 
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