Re: [alsa-devel] [Linux-kernel] [PATCH v5 2/7] ASoC: tegra: Allow 24bit and 32bit samples

From: Ben Dooks <ben.dooks@codethink.co.uk>
To: Dmitry Osipenko <digetx@gmail.com>, Jon Hunter <jonathanh@nvidia.com>
Cc: linux-kernel@lists.codethink.co.uk, alsa-devel@alsa-project.org,
	Liam Girdwood <lgirdwood@gmail.com>,
	Takashi Iwai <tiwai@suse.com>, Mark Brown <broonie@kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Edward Cragg <edward.cragg@codethink.co.uk>,
	linux-tegra@vger.kernel.org
Subject: Re: [alsa-devel] [Linux-kernel] [PATCH v5 2/7] ASoC: tegra: Allow 24bit and 32bit samples
Date: Mon, 20 Jan 2020 17:36:53 +0000	[thread overview]
Message-ID: <f1f56dc5-c2d0-eb01-d68f-50f3f5d9fce1@codethink.co.uk> (raw)
In-Reply-To: <ebfaa0d3-1236-cac4-4bd8-4456a171d773@gmail.com>

On 20/01/2020 16:50, Dmitry Osipenko wrote:
> 08.01.2020 14:37, Jon Hunter пишет:
>>
>> On 07/01/2020 01:39, Dmitry Osipenko wrote:
>>> 06.01.2020 22:00, Ben Dooks пишет:
>>>> On 05/01/2020 10:53, Ben Dooks wrote:
>>>>>
>>>>>
>>>>> On 2020-01-05 01:48, Dmitry Osipenko wrote:
>>>>>> 05.01.2020 03:04, Ben Dooks пишет:
>>>>>>> [snip]
>>>>>>>
>>>>>>> I've just gone through testing.
>>>>>>>
>>>>>>> Some simple data tests show 16 and 32-bits work.
>>>>>>>
>>>>>>> The 24 bit case seems to be weird, it looks like the 24-bit expects
>>>>>>> 24 bit samples in 32 bit words. I can't see any packing options to
>>>>>>> do 24 bit in 24 bit, so we may have to remove 24 bit sample support
>>>>>>> (which is a shame)
>>>>>>>
>>>>>>> My preference is to remove the 24-bit support and keep the 32 bit in.
>>>>>>>
>>>>>>
>>>>>> Interesting.. Jon, could you please confirm that 24bit format isn't
>>>>>> usable on T30?
>>>>>
>>>>> If there is an option of 24 packed into 32, then I think that would work.
>>>>>
>>>>> I can try testing that with raw data on Monday.
>>>>
>>>> I need to check some things, I assumed 24 was 24 packed bits, it looks
>>>> like the default is 24 in 32 bits so we may be ok. However I need to
>>>> re-write my test case which assumed it was 24bits in 3 bytes (S24_3LE).
>>>>
>>>> I'll follow up later,
>>>
>>> Okay, the S24_3LE isn't supported by RT5640 codec in my case. I briefly
>>> looked through the TRM doc and got impression that AHUB could re-pack
>>> data stream into something that codec supports, but maybe it's a wrong
>>> impression.
>>
>> I chatted with Sameer about this, so yes the AHUB can repack, but there
>> is a problem with S24_LE where if we try to extract 24-bits we actually
>> get the upper 24-bits and not the lower LSBs in the 32-bit data element.
>> So actually we don't support S24_LE.
>>
>> Ben do you need 24-bit support or 32-bit or both?

I think the S24 should work unpacked. The packed just doesn't seem to
be an option on tegra2/tegra3 hardware (the manual does not talk about
it either).

I will try and get this looked at again on Thursday 23rd and see if
I can run some more tests with 24 sample data in the input format and
a logic analyser on the output.

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

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