Re: [PATCH] Fix OMAP4430 SDP Ethernet startup

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

Russell,

On 07/12/2018 15.57, Russell King - ARM Linux wrote:
> On Fri, Dec 07, 2018 at 03:40:13PM +0200, Peter Ujfalusi wrote:
>> Russell,
>>
>> On 07/12/2018 14.52, Russell King - ARM Linux wrote:
>>> It was noticed that unbinding and rebinding the KSZ8851 ethernet
>>> resulted in the driver reporting "failed to read device ID" at probe.
>>> Probing the reset line with a 'scope while repeatedly attempting to
>>> bind the driver in a shell loop revealed that the KSZ8851 RSTN pin is
>>> constantly held at zero, meaning the device is held in reset, and
>>> does not respond on the SPI bus.
>>>
>>> Experimentation with the startup delay on the regulator set to 50ms
>>> shows that the reset is positively released after 20ms.
>>>
>>> Schematics for this board are not available, and the traces are buried
>>> in the inner layers of the board which makes tracing where the RSTN pin
>>> extremely difficult.  We can only guess that the RSTN pin is wired to a
>>> reset generator chip driven off the ethernet supply, which fits the
>>> observed behaviour.
>>
>> Based on the schematics of the Blaze device (which should be very close
>> to SDP4430):
>>
>> TPS22902YFPR is used as the regulator switch (gpio48 controlled)
>> The VOUT is routed to  TPS3808G01DBV (SCH Note: Threshold set at 90%.
>> Vsense: 0.405V).
>>
>> According to the TPS3808 data sheet the RESET delay time when Ct is open
>> (this is the case in the schema): MIN/TYP/MAX: 12/20/28 ms.
>>
>> The 20ms you are seeing confirms this setup.
> 
> Thanks for the confirmation and information.  The Blaze schematics
> are also unavailable afaics.

Even with the delay I can not get the ethernet working on Blaze. It
supposed to be mostly the same HW as sdp (we load the same omap4-sdp.dtb).

[    2.576599] ks8851 spi0.0: spi0.0 supply vdd-io not found, using
dummy regulator
[    2.584045] ks8851 spi0.0: Linked as a consumer to regulator.0
[    2.584136] ks8851 spi0.0: Linked as a consumer to regulator.4
[    2.595916] ks8851 spi0.0: message enable is 0
[    2.602661] ks8851 spi0.0: failed to read device ID
[    2.607604] ks8851 spi0.0: Dropping the link to regulator.4
[    2.607604] ks8851 spi0.0: Dropping the link to regulator.0

I can not recall when was the last time it worked, could be years ago.

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

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