[U-Boot] FEC and EFI Simple Network

[Alexander Graf]

On 29.03.18 06:02, Joe Hershberger wrote:
> Hi Patrick,
> 
> On Wed, Mar 28, 2018 at 4:54 PM, Fabio Estevam <festevam at gmail.com> wrote:
>> Adding Joe in case he has some ideas.
>>
>> On Tue, Mar 27, 2018 at 9:12 AM, Patrick Wildt <patrick at blueri.se> wrote:
>>> Hi,
>>>
>>> I have been debugging network issues when running an EFI Application
>>> that uses the EFI Simple Network protocol on an i.MX6 machine (FEC).
>>>
>>> The symptom is that u-boot's (FEC) internal RX ring index is reset to 0,
>>> while the controller is still at idx 3 (or something else).  This is
>>> caused by the following circumstances:
>>>
>>> The Simple Network protocol offers methods like Start(), Stop(),
>>> Initialize(), Shutdown(), Reset().  Also the protocol has a state.  The
>>> states are Stopped, Started, Initialized.  The transition is as follows:
>>>
>>> Stopped ---Start()---> Started ---Initialize()--> Initialized
>>>
>>> Start() does some initialization, Initialize() allocates the TX/RX
>>> descriptors and actually kicks off the network engine.
>>>
>>> So far, only Initialize() is implemented in our u-boot interface, and it
>>> calls eth_init() which in the end calls fec_init().  Our network state
>>> is _always_ Started.  This means that EFI Applications see that that the
>>> state is Started and then call Initialize() to start the actual network
>>> traffic.  There is no call to Stop()/Shutdown()/Reset() as it's supposed
>>> to be in a sane state.
>>>
>>> In my case the FEC is already initialized since I booted using network
>>> and the RX desc index is already non-zero.  Now the EFI Application sees
>>> that the state is Started, calls Initialize() which makes u-boot call
>>> eth_init() which then calls fec_init().
>>>
>>> fec_init() does not reset the controller so that the controller-internal
>>> RX desc index is not reset to zero.  fec_init() calls fec_open() which
>>> then resets the driver-internal RX desc index to zero.  Now they are out
>>> of sync, boom.
> 
> Would it be reasonable for fec_init to use a state variable to keep
> track of if it (and the HW) is already initialized and not call
> fec_open in that case? Also, fec_halt would need to update that state
> as well.

Ping? Is this still an issue?


Alex