| Message ID | 20230214161435.1088246-1-claudiu.beznea@microchip.com |
|---|---|
| Headers | show |
| Series | ASoC: mchp-pdmc: fix poc noises when starting capture | expand |
On 14/02/2023 17:14, Claudiu Beznea wrote: > Add microchip,startup-delay-us binding to let PDMC users to specify > startup delay. > > Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> > --- > .../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. Is this some hardware delay? Or OS? If OS, why Linux specific delay is put into DT? Best regards, Krzysztof
On 16.02.2023 12:04, Krzysztof Kozlowski wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > On 14/02/2023 17:14, Claudiu Beznea wrote: >> Add microchip,startup-delay-us binding to let PDMC users to specify >> startup delay. >> >> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> >> --- >> .../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. > > Is this some hardware delay? Or OS? If OS, why Linux specific delay is > put into DT? It's the delay used in software workaround that IP needs to filter noises. The IP is not fully featured to do this kind of filtering on its own thus this software workaround. This delay may depend on used microphones thus for different kind of setups (PDMC + different microphones) I introduced this in DT. > > Best regards, > Krzysztof >
On 16/02/2023 11:15, Claudiu.Beznea@microchip.com wrote: > On 16.02.2023 12:04, Krzysztof Kozlowski wrote: >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe >> >> On 14/02/2023 17:14, Claudiu Beznea wrote: >>> Add microchip,startup-delay-us binding to let PDMC users to specify >>> startup delay. >>> >>> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> >>> --- >>> .../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. >> >> Is this some hardware delay? Or OS? If OS, why Linux specific delay is >> put into DT? > > It's the delay used in software workaround that IP needs to filter noises. Then this sounds like OS? Linux related properties usually do not belong to DT. > The IP is not fully featured to do this kind of filtering on its own thus > this software workaround. This delay may depend on used microphones thus > for different kind of setups (PDMC + different microphones) I introduced > this in DT. I understand your driver needs delay and I am not questioning this. I am questioning why this is suitable for DT? Best regards, Krzysztof
On 16.02.2023 12:18, Krzysztof Kozlowski wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > On 16/02/2023 11:15, Claudiu.Beznea@microchip.com wrote: >> On 16.02.2023 12:04, Krzysztof Kozlowski wrote: >>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe >>> >>> On 14/02/2023 17:14, Claudiu Beznea wrote: >>>> Add microchip,startup-delay-us binding to let PDMC users to specify >>>> startup delay. >>>> >>>> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> >>>> --- >>>> .../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. >>> >>> Is this some hardware delay? Or OS? If OS, why Linux specific delay is >>> put into DT? >> >> It's the delay used in software workaround that IP needs to filter noises. > > Then this sounds like OS? Linux related properties usually do not belong > to DT. > >> The IP is not fully featured to do this kind of filtering on its own thus >> this software workaround. This delay may depend on used microphones thus >> for different kind of setups (PDMC + different microphones) I introduced >> this in DT. > > I understand your driver needs delay and I am not questioning this. I am > questioning why this is suitable for DT? Because that delay may depend on the microphones that are used with PDMC. Different boards may come with different microphones, thus the default delay may not fit to fully filter the noise. Due to this I chose to add it in DT. > > > Best regards, > Krzysztof >
On 16/02/2023 11:41, Claudiu.Beznea@microchip.com wrote: > On 16.02.2023 12:18, Krzysztof Kozlowski wrote: >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe >> >> On 16/02/2023 11:15, Claudiu.Beznea@microchip.com wrote: >>> On 16.02.2023 12:04, Krzysztof Kozlowski wrote: >>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe >>>> >>>> On 14/02/2023 17:14, Claudiu Beznea wrote: >>>>> Add microchip,startup-delay-us binding to let PDMC users to specify >>>>> startup delay. >>>>> >>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com> >>>>> --- >>>>> .../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. >>>> >>>> Is this some hardware delay? Or OS? If OS, why Linux specific delay is >>>> put into DT? >>> >>> It's the delay used in software workaround that IP needs to filter noises. >> >> Then this sounds like OS? Linux related properties usually do not belong >> to DT. >> >>> The IP is not fully featured to do this kind of filtering on its own thus >>> this software workaround. This delay may depend on used microphones thus >>> for different kind of setups (PDMC + different microphones) I introduced >>> this in DT. >> >> I understand your driver needs delay and I am not questioning this. I am >> questioning why this is suitable for DT? > > Because that delay may depend on the microphones that are used with PDMC. > Different boards may come with different microphones, thus the default > delay may not fit to fully filter the noise. Due to this I chose to add it > in DT. Ah, ok, that's good explanation. Thank you. Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Best regards, Krzysztof
On Thu, Feb 16, 2023 at 11:18:16AM +0100, Krzysztof Kozlowski wrote: > On 16/02/2023 11:15, Claudiu.Beznea@microchip.com wrote: > >>> + 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. > >> Is this some hardware delay? Or OS? If OS, why Linux specific delay is > >> put into DT? > > It's the delay used in software workaround that IP needs to filter noises. > Then this sounds like OS? Linux related properties usually do not belong > to DT. This is a hardware property, it's the time needed for the input to settle.
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, driver sets its struct snd_dmaengine_pcm_config::start_dma_last = 1 and proper action is taken based on this flag when starting DAI trigger vs DMA. The other solution that was identified for this was to extend the already existing mechanism around struct snd_soc_dai_link::stop_dma_first. The downside of this was that a potential struct snd_soc_dai_link::start_dma_last would have to be populated on sound card driver thus, had to be taken into account in all sound card drivers. At the moment, the mchp-pdmc is used only with simple-audio-card. In case of simple-audio-card a new DT binding would had to be introduced to specify this action on dai-link descriptions (as of my investigation). Please advice what might be the best approach. Thank you, Claudiu Beznea Claudiu Beznea (3): ASoC: soc-generic-dmaengine-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/dmaengine_pcm.h | 1 + include/sound/soc-component.h | 2 + sound/soc/atmel/mchp-pdmc.c | 55 +++++++++++++++++-- sound/soc/soc-generic-dmaengine-pcm.c | 8 ++- sound/soc/soc-pcm.c | 27 +++++++-- 6 files changed, 86 insertions(+), 13 deletions(-)