[alsa-devel] fsl_ssi.c: Getting channel slips with fsl_ssi.c in TDM (network) mode.

[Caleb Crome]

On Wed, Oct 28, 2015 at 1:11 AM, Roberto Fichera <kernel at tekno-soft.it> wrote:
> On 10/27/2015 07:57 PM, Fabio Estevam wrote:
>> [Adding Roberto in the thread as he is also trying to get SSI TDM support/
>
> Thanks Fabio,
>
> I'm also having the same issue but employing SSI in TDM master mode against a SLIC Si32178
> using its PCM mode. PCLK is at 2048KHz, FSYNC is 8KHz slot length is 32 bits (SSI wants
> this since when in master mode) but valid data set to be 8bits in the SSI register.
>
> My Current situation is that I've a custom fsl_ssi.c driver to control the SSI in TDM master mode
> both PCLK and FSYNC works perfectly fine, the SLIC has a register that I can check via SPI for
> such purpose, I can see the clocking status from its side. The main problem I've is exactly the same
> Caleb is having, after a certain amount of SDMA transfers, roughly 1000 or so, everything stops
> without any apparent reason.

My problem is that the channels randomly slip a slot and all words end
up in the wrong slot.  I suspect this is a DMA issue, but I really
haven't diagnosed it yet.  I don't get a full stop on the data.

FYI, I'm using a very recent 4.3 kernel from linus's repo, but 4.2
behaved the same.

-Caleb

>
>>
>> On Tue, Oct 27, 2015 at 2:45 PM, Fabio Estevam <festevam at gmail.com> wrote:
>>> On Tue, Oct 27, 2015 at 2:42 PM, Caleb Crome <caleb at crome.org> wrote:
>>>> On Tue, Oct 27, 2015 at 9:10 AM, Fabio Estevam <festevam at gmail.com> wrote:
>>>>> On Tue, Oct 27, 2015 at 2:02 PM, Caleb Crome <caleb at crome.org> wrote:
>>>>>
>>>>>>> Could you please try it without using the external SDMA firmware?
>>>>>> I do need *some* SDMA firmware, correct?  The firmware that I'm using
>>>>>> ends up in /lib/firmware/imx/sdma/sdma-imx6q.bin and is md5sum
>>>>>> 5d4584134cc4cba62e1be2f382cd6f3a.
>>>>> SSI can operate with the ROM SDMA firmware.
>>>>>
>>>>> I would like to know if this issue also happens if you don't pass the
>>>>> external firmware and use the internal ROM SDMA firmware instead.
>>>> Ah, good to know.  Do I just remove reference in the .dtsi file?
>>>> Remove the file from the filesystem?  I'll do both to be doubly sure
>>>> :-)
>>> Just remove it from the rootfs. Then you will see a message from the
>>> kernel saying that no external SDMA firmware could be found and that
>>> the internal one is going to be used.
>>>
>>>>> Also, could you try bumping the SSI and SDMA clock rates at the maximum?
>>>> Any idea how I do that?  I guess it's in the .dtsi file perhaps?  I'll
>>>> poke around.
>>> You can try to call clk_set_rate() with the maximum allowed frequency
>>> inside the ssi driver. I don't recall on top of my head what is this
>>> value though.
>>>
>>> Regards,
>>>
>>> Fabio Estevam
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>