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

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Message-ID: <CAMuHMdWhY7nNanQ=h8HGrWyDfpCSL33QFJorhLCgnKASbmHiYw@mail.gmail.com>
Date: Mon, 26 Jan 2026 15:26:16 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu <claudiu.beznea@...on.dev>
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 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.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds