Hello Sudhakar,
On Fri, Feb 24, 2012 at 2:02 PM, Rajashekhara, Sudhakar <sudhakar....@ti.com>
wrote:
> On Thu, Feb 23, 2012 at 14:39:49, Christian Riesch wrote:
>> Hi,
>> I observed this behavior on a Texas Instruments AM1808 SoC (AM1808
>> experimenter's kit) running the current mainline kernel:
>>
>> # ifconfig eth0 down
>> # ifconfig eth0 up
>> davinci_mdio davinci_mdio.0: resetting idled controller
>> net eth0: attached PHY driver [Generic PHY]
>> (mii_bus:phy_addr=davinci_mdio-0:00)
>> # PHY: davinci_mdio-0:00 - Link is Up - 100/Full
>>
>
> I also observed this issue with the kernel from linux-davinci tree from
> gitorious.
>
>> After each ifconfig eth0 up I get this 'resetting idled controller'
>> warning. I added a few debug messages to the davinci_mdio driver and
>> noticed that the MDIO control register was set to its reset value
>> (clock divider 0xff and MDIO turned off) after an ifconfig eth0 up.
>> Therefore, this warning is issued and a reconfiguration of the MDIO
>> controller is done by the driver.
>>
>> Now the question was: Who is turning off the MDIO controller? After a
>> bit of debugging I found out that the reset of the MDIO controller
>> seems to be caused by these lines in the davinci_emac driver in
>> emac_hw_enable() in drivers/net/ethernet/ti/davinci_emac.c:
>>
>> emac_write(EMAC_SOFTRESET, 1);
>> while (emac_read(EMAC_SOFTRESET))
>> cpu_relax();
>>
>> According to the AM1808 Technical Reference Manual (sections 18.2.14.1
>> and 18.3.3.34 in [1]), writing a 1 to the EMAC_SOFTRESET register
>> resets the EMAC module, but not the MDIO module. However, when I
>> comment out the code above, the MDIO control register is not affected
>> and the warning 'resetting idled controller' disappears.
>>
>
> But this was not the case for me. Even after commenting out the above lines,
> I could still see that MDIO was getting reset.
Uh, I am sorry. I forgot to mention that there is a second
emac_write(EMAC_SOFTRESET,1); in emac_dev_stop() in davinci_emac.c.
This one must also be commented out to make the resetting idled controller
message go away.
The patch below shows that changes that I did. May I please ask you to try
again with these changes?
Regards, Christian
>
> During eth0 up, the smsc_phy_config_init() function calls the mdiobus_read()
> function. During this sequence if the MDIO state machine is in IDLE state,
> then MDIO is reset causing the above warning message to appear.
>
> In summary, EMAC reset is not causing the MDIO reset to happen.
---
drivers/net/ethernet/ti/davinci_emac.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/ti/davinci_emac.c
b/drivers/net/ethernet/ti/davinci_emac.c
index 4b2f545..733d538 100644
--- a/drivers/net/ethernet/ti/davinci_emac.c
+++ b/drivers/net/ethernet/ti/davinci_emac.c
@@ -1290,10 +1290,10 @@ static int emac_hw_enable(struct emac_priv *priv)
u32 val, mbp_enable, mac_control;
/* Soft reset */
- emac_write(EMAC_SOFTRESET, 1);
+/* emac_write(EMAC_SOFTRESET, 1);
while (emac_read(EMAC_SOFTRESET))
cpu_relax();
-
+*/
/* Disable interrupt & Set pacing for more interrupts initially */
emac_int_disable(priv);
@@ -1672,7 +1672,7 @@ static int emac_dev_stop(struct net_device *ndev)
netif_carrier_off(ndev);
emac_int_disable(priv);
cpdma_ctlr_stop(priv->dma);
- emac_write(EMAC_SOFTRESET, 1);
+/* emac_write(EMAC_SOFTRESET, 1);*/
if (priv->phydev)
phy_disconnect(priv->phydev);
--
1.7.0.4
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