linux-kernel - Re: [PATCH 6/7] ASoC: renesas: rz-ssi: Use generic PCM dmaengine APIs

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Message-ID: <74692e8a-220f-4248-9481-81bb331597f1@tuxon.dev>
Date: Mon, 26 Jan 2026 16:46:16 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: vkoul@...nel.org, biju.das.jz@...renesas.com,
 prabhakar.mahadev-lad.rj@...renesas.com, lgirdwood@...il.com,
 broonie@...nel.org, perex@...ex.cz, tiwai@...e.com, p.zabel@...gutronix.de,
 fabrizio.castro.jz@...esas.com, dmaengine@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-sound@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 6/7] ASoC: renesas: rz-ssi: Use generic PCM dmaengine APIs

Hi, Geert,

On 1/26/26 16:26, Geert Uytterhoeven wrote:
> Hi Claudiu,
> 
> On Mon, 26 Jan 2026 at 11:32, Claudiu <claudiu.beznea@...on.dev> wrote:
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> On Renesas RZ/G2L and RZ/G3S SoCs (where this was tested), captured audio
>> files occasionally contained random spikes when viewed with a profiling
>> tool such as Audacity. These spikes were also audible as popping noises.
>>
>> Using cyclic DMA resolves this issue. The driver was reworked to use the
>> existing support provided by the generic PCM dmaengine APIs. In addition
>> to eliminating the random spikes, the following issues were addressed:
>> - blank periods at the beginning of recorded files, which occurred
>>    intermittently, are no longer present
>> - no overruns or underruns were observed when continuously recording
>>    short audio files (e.g. 5 seconds) in a loop
>> - concurrency issues in the SSI driver when enqueuing DMA requests were
>>    eliminated; previously, DMA requests could be prepared and submitted
>>    both from the DMA completion callback and the interrupt handler, which
>>    led to crashes after several hours of testing
>> - the SSI driver logic is simplified
>> - the number of generated interrupts is reduced by approximately 250%
>>
>> In the SSI platform driver probe function, the following changes were
>> made:
>> - the driver-specific DMA configuration was removed in favor of the
>>    generic PCM dmaengine APIs. As a result, explicit cleanup goto labels
>>    are no longer required and the driver remove callback was dropped,
>>    since resource management is now handled via devres helpers
>> - special handling was added for IP variants operating in half-duplex
>>    mode, where the DMA channel name in the device tree is "rt"; this DMA
>>    channel name is taken into account and passed to the generic PCM
>>    dmaengine configuration data
>>
>> All code previously responsible for preparing and completing DMA
>> transfers was removed, as this functionality is now handled entirely by
>> the generic PCM dmaengine APIs.
>>
>> Since DMA channels must be paused and resumed during recovery paths
>> (overruns and underruns), the DMA channel references are stored in
>> rz_ssi_hw_params().
>>
>> The logic in rz_ssi_is_dma_enabled() was updated to reflect that the
>> driver no longer manages DMA transfers directly.
>>
>> Finally, rz_ssi_stream_is_play() was removed, as it had only a single
>> remaining user after this rework, and its logic was inlined at the call
>> site.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> 
> Thanks for your patch!
> 
>> --- a/sound/soc/renesas/rz-ssi.c
>> +++ b/sound/soc/renesas/rz-ssi.c
> 
>> @@ -1116,15 +936,19 @@ static struct snd_soc_dai_driver rz_ssi_soc_dai[] = {
>>   static const struct snd_soc_component_driver rz_ssi_soc_component = {
>>          .name                   = "rz-ssi",
>>          .open                   = rz_ssi_pcm_open,
>> -       .pointer                = rz_ssi_pcm_pointer,
>> -       .pcm_construct          = rz_ssi_pcm_new,
>>          .legacy_dai_naming      = 1,
>>   };
>>
>> +static struct snd_dmaengine_pcm_config rz_ssi_dmaegine_pcm_conf = {
>> +       .prepare_slave_config   = snd_dmaengine_pcm_prepare_slave_config,
> 
> This fails to link if CONFIG_SND_SOC_GENERIC_DMAENGINE_PCM is not
> enabled (e.g. renesas_defconfig):
> 
>      aarch64-linux-gnu-ld: sound/soc/renesas/rz-ssi.o: in function
> `rz_ssi_probe':
>      rz-ssi.c:(.text+0x538): undefined reference to
> `devm_snd_dmaengine_pcm_register'
>      aarch64-linux-gnu-ld: sound/soc/renesas/rz-ssi.o:(.data+0xc8):
> undefined reference to `snd_dmaengine_pcm_prepare_slave_config'
> 
> Adding a select like this white-space damaged snippet:
> 
>      --- a/sound/soc/renesas/Kconfig
>      +++ b/sound/soc/renesas/Kconfig
>      @@ -56,6 +56,7 @@ config SND_SOC_MSIOF
>       config SND_SOC_RZ
>              tristate "RZ/G2L series SSIF-2 support"
>              depends on ARCH_RZG2L || COMPILE_TEST
>      +       select SND_SOC_GENERIC_DMAENGINE_PCM
>              help
>                This option enables RZ/G2L SSIF-2 sound support.
> 
> would fix the build.

Thank you for reporting and proposing a fix. I'll take care of it in v2.

Claudiu