On Wed, May 6, 2009 at 2:21 PM, Wolfgang Denk
<wd@denx.de> wrote:
Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: John Rigby <jcrigby@gmail.com>
---
This patch is NOT intended for inclusion into mainline, but rather a
request for help. For some reason which I don't understand yet, the
Ethernet interface on the ARIA board does not work in the default
configuration, because MII probing fails.
What I'm seeing is this; the problem is with this part of code in
"drivers/net/fs_enet/mii-fec.c":
156 fec->mii_speed = ((ppc_proc_freq + 4999999) / 5000000) << 1;
...
163 out_be32(&fec->fecp->fec_mii_speed, fec->mii_speed);
I added some debug messages, and this is what I see:
On the ADS5121, we have the CPU clocked at 400 MHz. I get:
...
## ppc_proc_freq = 399999996, fec->mii_speed = 160
FEC MII Bus: probed
...
It works fine.
According to the Ref. Man.:
A value of 0 in this field turns off the MDC and leaves it in
a low-voltage state. Any non-zero value results in the MDC
frequency of 1/(mii_speed*2) of the system clock frequency.
that means we have a MDC frequency of
400 MHz / (2 * 160) = 1.25 MHz
which is obviously within the 2.5 MHz limit.
Now ARIA is currently running at 316.8 MHz, and this is what I get:
...
## ppc_proc_freq = 316800000, fec->mii_speed = 128
fsl-fec-mdio: probe of 80002800.mdio failed with error -5
...
It fails. MDC frequency is
316.8 MHz / (2 * 128) = 1.24 MHz
which should be fine.
However, If I change the code to
fec->mii_speed = (((ppc_proc_freq / 1000000) / 30) + 1) << 1;
then I get:
...
## ppc_proc_freq = 316800000, fec->mii_speed = 22
FEC MII Bus: probed
... and it's working!!! However, I compute MDC frequency as
316.8 MHz / (2 * 22) = 7.2 MHz
which is far above the maximum allowed clock of 2.5 MHz ???
Has anybody any idea what might be going on here?
drivers/net/fs_enet/mii-fec.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/drivers/net/fs_enet/mii-fec.c b/drivers/net/fs_enet/mii-fec.c
index 9d8bd97..a51dd83 100644
--- a/drivers/net/fs_enet/mii-fec.c
+++ b/drivers/net/fs_enet/mii-fec.c
@@ -153,8 +153,12 @@ static int __devinit fs_enet_mdio_probe(struct of_device *ofdev,
if (!fec->fecp)
goto out_fec;
+#if 0
fec->mii_speed = ((ppc_proc_freq + 4999999) / 5000000) << 1;
-
+#else
+ fec->mii_speed = (((ppc_proc_freq / 1000000) / 30) + 1) << 1;
+ printk("## ppc_proc_freq = %d, fec->mii_speed = %d\n", ppc_proc_freq, fec->mii_speed);
+#endif
setbits32(&fec->fecp->fec_r_cntrl, FEC_RCNTRL_MII_MODE);
setbits32(&fec->fecp->fec_ecntrl, FEC_ECNTRL_PINMUX |
FEC_ECNTRL_ETHER_EN);
--
1.6.0.6