[PATCH v3 0/3] ASoC: mchp-pdmc: fix poc noises when starting capture

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Claudiu Beznea

28 Feb 2023 28 Feb '23

12:01 p.m.

To start capture on Microchip PDMC the enable bits for each supported microphone need to be set. After this bit is set the PDMC starts to receive data from microphones and it considers this data as valid data. Thus if microphones are not ready the PDMC captures anyway data from its lines. This data is interpreted by the human ear as poc noises.

To avoid this the following software workaround need to be applied when starting capture: 1/ enable PDMC channel 2/ wait 150ms 3/ execute 16 dummy reads from RHR 4/ clear interrupts 5/ enable interrupts 6/ enable DMA channel

For this workaround to work step 6 need to be executed at the end. For step 6 was added patch 1/3 from this series. With this, component DAI driver sets its struct snd_soc_component_driver::start_dma_last = 1 and proper action is taken based on this flag when starting DAI trigger vs DMA.

Thank you, Claudiu Beznea

Changes in v3: - update the commit message of patch 2/3 to be more descriptive - in patch 3/3 initialize dd->startup_delay_us before calling of_property_read_u32() and don't check its return value; property is optional and the the default value is 150ms

Changes in v2: - patch 1/3 from v1 is now "ASoC: soc-pcm: add option to start DMA after DAI" - pass start_dma_last from component DAI driver object (struct snd_soc_component_driver::start_dma_last); adapt patch 3/3 after this; - in patch 1/3 s/Do we need to start dma first/Do we need to start dma last in comment from soc_pcm_trigger() - collect review tag from Krzysztof

Claudiu Beznea (3): ASoC: soc-pcm: add option to start DMA after DAI ASoC: dt-bindings: sama7g5-pdmc: add microchip,startup-delay-us binding ASoC: mchp-pdmc: fix poc noise at capture startup

.../sound/microchip,sama7g5-pdmc.yaml | 6 +++ include/sound/soc-component.h | 2 + sound/soc/atmel/mchp-pdmc.c | 53 +++++++++++++++++-- sound/soc/soc-pcm.c | 27 ++++++++-- 4 files changed, 78 insertions(+), 10 deletions(-)

-- 2.34.1

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Claudiu Beznea

28 Feb 28 Feb

12:01 p.m.

New subject: [PATCH v3 1/3] ASoC: soc-pcm: add option to start DMA after DAI

Add option to start DMA component after DAI trigger. This is done by filling the new struct snd_soc_component_driver::start_dma_last.

Signed-off-by: Claudiu Beznea claudiu.beznea@microchip.com --- include/sound/soc-component.h | 2 ++ sound/soc/soc-pcm.c | 27 ++++++++++++++++++++++----- 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/include/sound/soc-component.h b/include/sound/soc-component.h index 3203d35bc8c1..0814ed143864 100644 --- a/include/sound/soc-component.h +++ b/include/sound/soc-component.h @@ -190,6 +190,8 @@ struct snd_soc_component_driver { bool use_dai_pcm_id; /* use DAI link PCM ID as PCM device number */ int be_pcm_base; /* base device ID for all BE PCMs */

+ unsigned int start_dma_last; + #ifdef CONFIG_DEBUG_FS const char *debugfs_prefix; #endif diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index 005b179a770a..5eb056b942ce 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -1088,22 +1088,39 @@ static int soc_pcm_hw_params(struct snd_pcm_substream *substream, static int soc_pcm_trigger(struct snd_pcm_substream *substream, int cmd) { struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream); - int ret = -EINVAL, _ret = 0; + struct snd_soc_component *component; + int ret = -EINVAL, _ret = 0, start_dma_last = 0, i; int rollback = 0;

switch (cmd) { case SNDRV_PCM_TRIGGER_START: case SNDRV_PCM_TRIGGER_RESUME: case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: + /* Do we need to start dma last? */ + for_each_rtd_components(rtd, i, component) { + if (component->driver->start_dma_last) { + start_dma_last = 1; + break; + } + } + ret = snd_soc_link_trigger(substream, cmd, 0); if (ret < 0) goto start_err;

- ret = snd_soc_pcm_component_trigger(substream, cmd, 0); - if (ret < 0) - goto start_err; + if (start_dma_last) { + ret = snd_soc_pcm_dai_trigger(substream, cmd, 0); + if (ret < 0) + goto start_err; + + ret = snd_soc_pcm_component_trigger(substream, cmd, 0); + } else { + ret = snd_soc_pcm_component_trigger(substream, cmd, 0); + if (ret < 0) + goto start_err;

- ret = snd_soc_pcm_dai_trigger(substream, cmd, 0); + ret = snd_soc_pcm_dai_trigger(substream, cmd, 0); + } start_err: if (ret < 0) rollback = 1;

-- 2.34.1

Claudiu Beznea

12:01 p.m.

New subject: [PATCH v3 2/3] ASoC: dt-bindings: sama7g5-pdmc: add microchip,startup-delay-us binding

PDMC can work with different types of microphones, thus different boards could have different microphones. Depending on microphone type the PDMC would need to wait longer or shorter period (at startup) than the default chosen one to filter unwanted noise. Thus add microchip,startup-delay-us binding to let PDMC users to specify startup delay.

Signed-off-by: Claudiu Beznea claudiu.beznea@microchip.com Reviewed-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org --- .../devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml b/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml index c4cf1e5ab84b..9b40268537cb 100644 --- a/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml +++ b/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml @@ -67,6 +67,12 @@ properties: maxItems: 4 uniqueItems: true

+ microchip,startup-delay-us: + description: | + Specifies the delay in microseconds that needs to be applied after + enabling the PDMC microphones to avoid unwanted noise due to microphones + not being ready. + required: - compatible - reg

-- 2.34.1

Claudiu Beznea

12:01 p.m.

New subject: [PATCH v3 3/3] ASoC: mchp-pdmc: fix poc noise at capture startup

Microchip PDMC IP doesn't filter microphone noises on startup. By default, it captures data received from digital microphones after the MCHP_PDMC_MR.EN bits are set. Thus when enable is set on PDMC side the digital microphones might not be ready yet and PDMC captures data from then in this time. This data captured is poc noise. To avoid this the software workaround is to the following: 1/ enable PDMC channel 2/ wait 150ms (on SAMA7G5-EK setup) 3/ execute 16 dummy reads from RHR 4/ clear interrupts 5/ enable interrupts 6/ enable DMA channel

Fixes: 50291652af52 ("ASoC: atmel: mchp-pdmc: add PDMC driver") Signed-off-by: Claudiu Beznea claudiu.beznea@microchip.com --- sound/soc/atmel/mchp-pdmc.c | 53 +++++++++++++++++++++++++++++++++---- 1 file changed, 48 insertions(+), 5 deletions(-)

diff --git a/sound/soc/atmel/mchp-pdmc.c b/sound/soc/atmel/mchp-pdmc.c index cf4084dcbd5e..1aed3baa9369 100644 --- a/sound/soc/atmel/mchp-pdmc.c +++ b/sound/soc/atmel/mchp-pdmc.c @@ -114,6 +114,7 @@ struct mchp_pdmc { struct clk *gclk; u32 pdmcen; u32 suspend_irq; + u32 startup_delay_us; int mic_no; int sinc_order; bool audio_filter_en; @@ -425,6 +426,7 @@ static const struct snd_soc_component_driver mchp_pdmc_dai_component = { .open = &mchp_pdmc_open, .close = &mchp_pdmc_close, .legacy_dai_naming = 1, + .start_dma_last = 1, };

static const unsigned int mchp_pdmc_1mic[] = {1}; @@ -632,6 +634,29 @@ static int mchp_pdmc_hw_params(struct snd_pcm_substream *substream, return 0; }

+static void mchp_pdmc_noise_filter_workaround(struct mchp_pdmc *dd) +{ + u32 tmp, steps = 16; + + /* + * PDMC doesn't wait for microphones' startup time thus the acquisition + * may start before the microphones are ready leading to poc noises at + * the beginning of capture. To avoid this, we need to wait 50ms (in + * normal startup procedure) or 150 ms (worst case after resume from sleep + * states) after microphones are enabled and then clear the FIFOs (by + * reading the RHR 16 times) and possible interrupts before continuing. + * Also, for this to work the DMA needs to be started after interrupts + * are enabled. + */ + usleep_range(dd->startup_delay_us, dd->startup_delay_us + 5); + + while (steps--) + regmap_read(dd->regmap, MCHP_PDMC_RHR, &tmp); + + /* Clear interrupts. */ + regmap_read(dd->regmap, MCHP_PDMC_ISR, &tmp); +} + static int mchp_pdmc_trigger(struct snd_pcm_substream *substream, int cmd, struct snd_soc_dai *dai) { @@ -644,15 +669,17 @@ static int mchp_pdmc_trigger(struct snd_pcm_substream *substream, switch (cmd) { case SNDRV_PCM_TRIGGER_RESUME: case SNDRV_PCM_TRIGGER_START: - /* Enable overrun and underrun error interrupts */ - regmap_write(dd->regmap, MCHP_PDMC_IER, dd->suspend_irq | - MCHP_PDMC_IR_RXOVR | MCHP_PDMC_IR_RXUDR); - dd->suspend_irq = 0; - fallthrough; case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: snd_soc_component_update_bits(cpu, MCHP_PDMC_MR, MCHP_PDMC_MR_PDMCEN_MASK, dd->pdmcen); + + mchp_pdmc_noise_filter_workaround(dd); + + /* Enable interrupts. */ + regmap_write(dd->regmap, MCHP_PDMC_IER, dd->suspend_irq | + MCHP_PDMC_IR_RXOVR | MCHP_PDMC_IR_RXUDR); + dd->suspend_irq = 0; break; case SNDRV_PCM_TRIGGER_SUSPEND: regmap_read(dd->regmap, MCHP_PDMC_IMR, &dd->suspend_irq); @@ -796,6 +823,7 @@ static bool mchp_pdmc_readable_reg(struct device *dev, unsigned int reg) case MCHP_PDMC_CFGR: case MCHP_PDMC_IMR: case MCHP_PDMC_ISR: + case MCHP_PDMC_RHR: case MCHP_PDMC_VER: return true; default: @@ -817,6 +845,17 @@ static bool mchp_pdmc_writeable_reg(struct device *dev, unsigned int reg) } }

+static bool mchp_pdmc_volatile_reg(struct device *dev, unsigned int reg) +{ + switch (reg) { + case MCHP_PDMC_ISR: + case MCHP_PDMC_RHR: + return true; + default: + return false; + } +} + static bool mchp_pdmc_precious_reg(struct device *dev, unsigned int reg) { switch (reg) { @@ -836,6 +875,7 @@ static const struct regmap_config mchp_pdmc_regmap_config = { .readable_reg = mchp_pdmc_readable_reg, .writeable_reg = mchp_pdmc_writeable_reg, .precious_reg = mchp_pdmc_precious_reg, + .volatile_reg = mchp_pdmc_volatile_reg, .cache_type = REGCACHE_FLAT, };

@@ -918,6 +958,9 @@ static int mchp_pdmc_dt_init(struct mchp_pdmc *dd) dd->channel_mic_map[i].clk_edge = edge; }

+ dd->startup_delay_us = 150000; + of_property_read_u32(np, "microchip,startup-delay-us", &dd->startup_delay_us); + return 0; }

-- 2.34.1

Mark Brown

7 p.m.

On Tue, 28 Feb 2023 13:01:42 +0200, Claudiu Beznea wrote:

...

To start capture on Microchip PDMC the enable bits for each supported microphone need to be set. After this bit is set the PDMC starts to receive data from microphones and it considers this data as valid data. Thus if microphones are not ready the PDMC captures anyway data from its lines. This data is interpreted by the human ear as poc noises.

To avoid this the following software workaround need to be applied when starting capture: 1/ enable PDMC channel 2/ wait 150ms 3/ execute 16 dummy reads from RHR 4/ clear interrupts 5/ enable interrupts 6/ enable DMA channel

[...]

Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/3] ASoC: soc-pcm: add option to start DMA after DAI commit: 54fc4b72b630e1cb92a21140084c6852babbb234 [2/3] ASoC: dt-bindings: sama7g5-pdmc: add microchip,startup-delay-us binding commit: 143a2f011c4471511887807822d3fd71f25f5169 [3/3] ASoC: mchp-pdmc: fix poc noise at capture startup commit: c5682e2ba1327d08987a7cabc7b5b40bf3bc131f

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying to this mail.

Thanks, Mark

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Claudiu Beznea
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