Re: [PATCH v2 1/2] spi: add check_finished() callback

[Hauke Mehrtens <hauke@xxxxxxxxxx>]

On 01/10/2017 01:34 PM, Mark Brown wrote:
> On Sat, Dec 17, 2016 at 11:16:17PM +0100, Hauke Mehrtens wrote:
>> On 12/14/2016 04:21 PM, Mark Brown wrote:
> 
>>> Why not just have your interrupt handler schedule something on a
>>> workqueue to check whatever it is needs checking here?
> 
>> 2. When something went wrong and I got an error IRQ for example, I would
>> like to add this information to the spi message that was transfered, but
>> the only way I see it to not wake the completion and let it run into a
>> timeout.
> 
> Just set an error status in the message and then complete the current
> transfer or the message.
> 
>> I would like to have a function in which I can do some busy waiting till
>> the last word is really written to the wire and also return if the
>> transfer was successful or what error occurred.
> 
> The busy waiting really is pretty specialist.

What should I do now?

I can add the transfer status in some other way, no problem, but how do
I tell Linux that the transfer finished when it really finished. I also
tried to just ignore the last word, but when the controller is
configured for the next transfer, the old one gets corrupted.

There is a per transfered word IRQ, I can use that, but it is probably
triggered very often and I do not know if it works in all situations and
it has to get synced with the fifo IRQs which is probably complicated.

I can also start my own driver thread to do the busy waiting and trigger
the spi_finalize_current_transfer() later after busy waiting in the driver.

I can also use transfer_one_message()

I would prefer to add an additional busy waiting after the
wait_for_completion_timeout() like I did in this patch, but how should
this look like?

Hauke
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