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

[Roberto Fichera]

On 10/29/2015 05:39 PM, Caleb Crome wrote:
> On Thu, Oct 29, 2015 at 9:34 AM, Roberto Fichera <kernel at tekno-soft.it> wrote:
>> On 10/29/2015 05:02 PM, Roberto Fichera wrote:
>>> On 10/29/2015 04:54 PM, Caleb Crome wrote:
>>>> On Thu, Oct 29, 2015 at 8:37 AM, Roberto Fichera <kernel at tekno-soft.it> wrote:
>>>>> On 10/29/2015 03:55 PM, Caleb Crome wrote:
>>>>>> On Thu, Oct 29, 2015 at 6:44 AM, Caleb Crome <caleb at crome.org> wrote:
>>>>>>> On Wed, Oct 28, 2015 at 9:53 PM, Nicolin Chen <nicoleotsuka at gmail.com> wrote:
>>>>>>>> I am actually thinking about setting a watermark to a larger number.
>>>>>>>> I forgot how the SDMA script handles this number. But if this burst
>>>>>>>> size means the overall data count per transaction, it might indicate
>>>>>>>> that each FIFO only gets half of the burst size due to dual FIFOs.
>>>>>>>>
>>>>>>>> Therefore, if setting watermark to 8, each FIFO has 7 (15 - 8) space
>>>>>>>> left, the largest safe burst size could be 14 (7 * 2) actually.
>>>>>>> Oh, does this depend on the data size?  I'm using 16-bit data, so I
>>>>>>> guess the bursts are measured in 2 byte units?  Does this mean that
>>>>>>> the burst size should be dynamically adjusted depending on word size
>>>>>>> (I guess done in hw_params)?
>>>>>>>
>>>>>>>> Nicolin
>>>>>> Okay, so wm=8 and maxburst=14 definitely does not work at all,.  wm=8,
>>>>>> maxburst=8 works okay, but still not perfect.
>>>>>>
>>>>>> I just discovered some new information:
>>>>>>
>>>>>> With wm=8 and maxburst=8 (which is my best setting so far), I just
>>>>>> captured a problem at the very start of playing a file, and restarted
>>>>>> enough times to capture it starting wrong:
>>>>>>
>>>>>> Instead of the playback starting with
>>>>>>
>>>>>> (hex numbers:  my ramp file has first nibble as channel, second nibble as frame)
>>>>>>
>>>>>> frame 0:  00, 10, 20, 30, 40, 50, 60, 70, 80, 90, a0, b0, c0, d0, e0, f0
>>>>>> frame 1:  01, 11, 21, 31, 41, 51, 61, 71, 81, 91, a1, b1, c1, d1, e1, f1
>>>>>>
>>>>>> It started with:
>>>>>>
>>>>>> frame 0:  00, 00, 10, 20, 30, 40, 50, 60, 70, 80, 90, a0, b0, c0, d0, e0
>>>>>> frame 1:  f0, 01, 11, 21, 31, 41, 51, 61, 71, 81, 91, a1, b1, c1, d1, e1
>>>>>>
>>>>>> So, the transfer started wrong right out of the gate -- with an extra
>>>>>> sample inserted at the beginning. Again, my setup is:
>>>>>> 1) use scope to capture the TDM bus.  Trigger on first data change
>>>>>> 2) aplay myramp.wav
>>>>>> 3) If okay, ctrl-c and goto 2.
>>>>>> 4) The capture below shows everything off by 1 sample.
>>>>>>
>>>>>> The capture is here:
>>>>>> https://drive.google.com/open?id=0B-KUa9Yf1o7iOXFtWXk2ZXdoUXc
>>>>>>
>>>>>> This test definitely reveals that there is a startup issue.  Now for
>>>>>> the $64,000 question: what to do with this knowledge?  I'm quite
>>>>>> unfamiliar with how the DMA works at all.
>>>>> I'm my case for example, I'm using a iMX6SX SoC, I've changed fsl_ssi.c to start the SSI
>>>>> clock generated internally by setting both RDMAE and TDMAE just once I'm pretty sure
>>>>> that everything has been setup (DMA and callback). Note that I'm not using alsa because,
>>>>> my target is to integrate SSI in TDM network mode with my DAHDI driver for VoIP app.
>>>>>
>>>>> Back to the DMA question, in your case shouldn't be really a problem since all DMA
>>>>> stuff is handled by the linux audio framework.
>>>>>
>>>>> Regarding my SSI problem, I was able to keep the DMA working for few second once before
>>>>> it get stopped and never retriggered. Currently I've 2 DMA channel one for TX and another for RX
>>>>> I've changed my DTS and update my fsl_ssi to handle new clocks, I guess only the CLK_SPBA
>>>>> has improved my situation. I've also tried to enable both RIE and TIE to service the ISR, with
>>>>> and without SSI DMA support, but this end with a full system freeze.
>>>> I got this system freeze too when enabling RIE and TIE because the
>>>> interrupts TFE1IE, TFE0IE, TDE1IE, TDE0IE are *enabled* at reset.
>>>> (Check ref manual 61.9.5).   which I suspect was a livelock kind of
>>>> situation where the ISR is just called infinitely often.  After
>>>> disabling those, then the system worked okay.  Check out the previous
>>>> patch I sent on the issue yesterday or the day before.
>>> Ooohh!!! Forgot to check this!!! I'm now going to mask them!!!
>> Doesn't work for me! Still freeze the system!  SIER=0x01d005f4

I thought the same but setting only RFF0, TFE0, RDMAE and TDMAE along the RIE and TIE still free the system.

> You still have many per-frame interrupts enabled, which is still too
> many enabled.  for example, you have RLSIE, TLSIE, RFSIE, TFSIE, etc.
> These all generate one interrupt per frame, and not necessarily at the
> same time, so you could be having 4 or more interrupts per frame.  Be
> sure they're all zero except for the DMA enable and the specific ones
> you actually want enabled.

Yep! But I still think that the CPU should be able to handle all them.

>
> -C
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