Users of SBE FIFO kernel driver

[Venkatesh Sainath]

On 04/02/17 12:52 AM, Christopher Bostic wrote:
>
>
> On 2/1/17 10:48 PM, Venkatesh Sainath wrote:
>> I believe there are 2 drivers here. SBE FIFO driver and SBEI protocol 
>> driver. The SBEI protocol driver is the only user for the submit 
>> operation of SBE FIFO driver (as it requires the protocol knowledge 
>> to communicate with SBE). The SBEI protocol driver will be used by 
>> OCC and any user-space application that may want to perform a direct 
>> HW access over FSI  ( for eg any scom operation).
>>
> If I understand then the lowest level device driver in the kernel is 
> the sbe_fifo driver running on OpenFSI.
> The only thing that should have direct access to this is the sbei 
> protocol driver - via sbe_fifo submit operations.
>
> Any other code wishing to access the SBE FIFO engine must go through 
> the sbei protocol driver.  This would include
> OCC hwmon driver, SCOM device driver, as well as any user space 
> applications like host debugger/chip ops (potentially boot sequence if 
> in fact sbe fifo access is required).
>
> sbei protocol driver must then provide a means for user space to 
> access it.
I agree.
>
> Where do we stand with the sbei protocol device driver?  Who owns this 
> and is it complete?
>
The plan was to port the sbei protocol driver developed on FSP based 
systems. Chris: I believe Dhruvaraj discussed with you about this driver 
when he was in Austin. I can share the latest version of this driver.
>>
>> On 02/02/17 8:59 AM, Joel Stanley wrote:
>>> Hi Chris,
>>>
>>> On Thu, Feb 2, 2017 at 5:58 AM, Christopher Bostic
>>> <cbostic at linux.vnet.ibm.com> wrote:
>>>> I've not seen this discussed in the group but if this has already been
>>>> determined than any pointers to the latest documentation would be
>>>> appreciated.
>>>>
>>>> Who are all the potential users of the OpenBMC SBE FIFO device 
>>>> driver?   I
>>>> understand it will need to export its general submit interface to 
>>>> other
>>>> kernel drivers.  Only one I know of for sure would be the OCC 
>>>> driver Eddie
>>>> James is working on.
>>> In addition to Eddie's driver, in userspace we will have the code that
>>> performs the power on sequence.
>>>
>>>> Any others?
>>>>
>>>> What about user space access of the SBE FIFO engine?  What apps would
>>>> require it?  Cronus I assume will need some means to directly 
>>>> access it.
>>> We want userspace API and an in-kernel API.
>>>
>>> The driver you design will need to take into account that there will
>>> be multiple users from each of these APIs. For instance, there will be
>>> Eddie's OCC hwmon driver and the userspace code that kicks off the
>>> boot sequence.
>>>
>>> Cheers,
>>>
>>> Joel
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>>
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