[BUG][MTL] SSP File is completely silent 24in32bit

[wszypelt]

Describe the bug
Issue was created after merging 87856a7
Request for revert and repair

Issue with I2S with config 24in32bit
ERROR:SSP File is completely silent (5s_i2sssp_1_24000_4_24_32_buffers_1_1_1_1.wav). Average samples amplitude: 0.25%.

To Reproduce
pytest -s "tests/ace/fw_113_ssp/test_02_ssp_internal_loop.py::TestSspInternalLoop::test_113_02_simple_internal_loopback[24000Hz_24in32bit_4ch-ssp_1_to_ssp_1]"

Reproduction Rate
100%

Expected behavior
File not silent

Impact
all I2S tests with config 24in32bit

Environment

1. • SOF: 87856a7

• Platform: MTL

Topology

        """
        OBJECTIVE:
        SSP (I2S mode) internal loopback test.

        TEST STEPS:
        1. Load FW.
        2. Create topology with audio format and SSP instance as in title:
            - Host Output Copier->I2S TX Copier (internal loopback enabled)
            - I2S RX Copier->Host Input Copier (internal loopback enabled)
        3. Run pipelines and streams (5 seconds).
        4. Verify amount of unhandled notification - proper value is 0.
        5. Perform SNR comparison verification method of played and
            recorded file and verify it meets quality criteria.

        PASS CRITERIA:
        All steps passed successfully

        PIPELINES TOPOLOGY::
        +--------------------------------+
        | COPIER_HOST < -- COPIER_SSP-+  |
        |                             |  |
        |                             |  |
        | COPIER_HOST -- > COPIER_SSP-+  |
        +--------------------- ----------+
        """

Screenshots or console output

Logs:
i2s_1_24000_4_24_32_buffers_1_1_1_1.zip
grabbed_fw_logs_0.txt

[mengdonglin]

@RanderWang Can you help give a check?

[wszypelt]

@mengdonglin @RanderWang CI is not working properly because of this issue, please revert, then fix the errors

[wszypelt]

after the revert, the error does not occur

[RanderWang]

@lgirdwood @marcinszkudlinski @kv2019i @wszypelt I made great effort and finally found the root reason.

The pipelines are showed in the following graph. All the 4 copiers use 24/32 MSB sample type.

        PIPELINES TOPOLOGY::
        +--------------------------------+
        | COPIER_HOST < -- COPIER_SSP-+  |
        |                             |  |
        |                             |  |
        | COPIER_HOST -- > COPIER_SSP-+  |
        +--------------------- ----------+

The original code choose conversion function : convert_s32_to_s24, copy_stream, copy_stream, convert_s24_to_s32. (this conversion is incorrect for single playback and only work for loop back test but it was not detected by CI test)
My PR change it to : copy_stream, copy_stream, copy_stream, copy_stream. This works on Linux tests but is failed with the CI test. Why ?

l did many tests then found it was caused by SSP setting

SOF:
ffffff10 c1d0077f d0700004 00000000
02200000 00000003 00000003 00004002
00000000 07070000 00000020 00110001
00000fff

CI test:
00000000 81D00F37 C0700004 00000000
02990000 00000103 00000103 00004002
00000000 07070F00 00000020 00000000
00000000

SOF use 32bits frame width for SSP port but CI use 25 bit frame width with 1 dummy bits. So if converting stream with copy_stream function the MSB 8bits will be clamped by CI blob, but it works with SOF blob. The original code is very lucky to workaround this CI setting.

SOF use 32bits frame width which can deal with different formats and this makes Linux kernel driver easy to set I2S codec to use 32bits format for all cases. How to deal with this CI blob setting ? The real usage on Windows, Linux and chrome don't use this blob, do we need to hack FW to support it ?

// hack in FW
if ( gateway == ssp && 24bit MSB && it is playback)  // we may need to detect this is called by python test or normal Linux....
        use S32_to_S24 conversion function
else if (gateway == ssp && 24bit MSB && it is capture)
        use S24_to_S32 conversion function