renesas,ra-pdm
Description
One channel of the Renesas RA Pulse Density Modulation Interface (PDM-IF).
Each channel has its own data pin, filter chain and data buffer, and is
described by its own node. The chain is a sinc decimator, then a high pass
filter that removes the modulator's DC bias, then a compensation filter that
corrects the sinc filter's passband droop, then a half band low pass filter
that rejects what the final decimation would otherwise alias into the band.
Every coefficient below defaults to its register's reset value; together
those are the module's voice band setting, a 100 Hz high pass corner and a
7 kHz low pass corner, which is what capture at 16 kHz wants. A design
capturing at another rate wants a chain designed for it, which the hardware
manual does not tabulate. A channel samples its own PDMDATn pin on the
rising edge of PDM_CLKn, or the pin of the channel below it on the falling
edge, which is how two microphones sharing one data line are read.
Properties
Node specific properties
Properties not inherited from the base binding file.
Name |
Type |
Details |
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PDM-IF channel this node describes, which selects the PDMDATn and
PDMCLKn pins it drives.
This property is required. Legal values: |
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Pin configuration/s for the first state. Content is specific to the
selected pin controller driver implementation.
This property is required. |
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Names for the provided states. The number of names needs to match the
number of states.
This property is required. |
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Order of the sinc filter that decimates the one-bit stream. A higher
order rejects more of the modulator's shaped noise and needs more of the
twenty-bit output range for the filter's own gain. The default is the
reset value of the mode setting register.
Default value: Legal values: |
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Sample the data pin of the channel below this one on the falling edge of
its clock, rather than this channel's own pin on the rising edge. A PDM
microphone whose select input is tied high drives the line on the falling
edge, so a pair sharing one line is read as this channel and the one
above it. Channel 0 reads channel 2's pin.
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Right shift applied to the low pass filter's input, in bits. Shifting
trades headroom for resolution where a loud microphone would otherwise
saturate the filter. The default is the reset value.
Default value: Legal values: |
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Right shift applied to the compensation filter's input, in bits. The
default is the reset value.
Default value: Legal values: |
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Right shift applied to the high pass filter's input, in bits. The
default is the reset value.
Default value: Legal values: |
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High pass filter s(0) coefficient, as 16-bit signed data with fourteen
fraction bits. The reset value puts the corner at 100 Hz.
Default value: |
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High pass filter k(1) coefficient, in the same format as s(0).
Default value: |
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The high pass filter's two h coefficients, h(0) and h(1).
Default value: |
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The eleven h coefficients of the compensation filter, which flattens the
droop the sinc filter leaves across the passband.
Default value: |
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Centre coefficient of the half band low pass filter, which is also the
final decimation by two. The reset values put the corner at 7 kHz.
Default value: |
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The twenty remaining coefficients of the half band low pass filter.
Default value: |
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Pin configuration/s for the second state. See pinctrl-0.
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Pin configuration/s for the third state. See pinctrl-0.
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Pin configuration/s for the fourth state. See pinctrl-0.
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Pin configuration/s for the fifth state. See pinctrl-0.
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Deprecated node specific properties
Deprecated properties not inherited from the base binding file.
(None)
Base properties
Properties inherited from the base binding file, which defines common properties that may be set on many nodes. Not all of these may apply to the “renesas,ra-pdm” compatible.
Name |
Type |
Details |
|---|---|---|
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Information used to address the device. The value is specific to
the device (i.e. is different depending on the compatible
property).
The "reg" property is typically a sequence of (address, length) pairs.
Each pair is called a "register block". Values are
conventionally written in hex.
For details, see "2.3.6 reg" in Devicetree Specification v0.4.
This property is required. See Important properties for more information. |
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Information about the device's clock providers. In general, this property
should follow conventions established in the dt-schema binding:
https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/clock/clock.yaml
This property is required. |
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Must be "pclk" for the peripheral bus clock the module-stop bit belongs
to, followed by "pdmifclk" for the node supplying PDMIFCLK. The driver
divides the PDMIFCLK rate down to the microphone clock, so the second
entry has to carry a "clock-frequency".
This property is required. |
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Information about interrupts generated by the device, encoded as an array
of one or more interrupt specifiers. The format of the data in this property
varies by where the device appears in the interrupt tree. Devices with the same
"interrupt-parent" will use the same format in their interrupts properties.
For details, see "2.4 Interrupts and Interrupt Mapping" in
Devicetree Specification v0.4.
This property is required. See Important properties for more information. |
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Must be "dat" for the data reception interrupt and "err" for the error
detection interrupt of this channel.
This property is required. |
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Indicates the operational status of the hardware or other
resource that the node represents. In particular:
- "okay" means the resource is operational and, for example,
can be used by device drivers
- "disabled" means the resource is not operational and the system
should treat it as if it is not present
For details, see "2.3.4 status" in Devicetree Specification v0.4.
Legal values: See Important properties for more information. |
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This property is a list of strings that essentially define what
type of hardware or other resource this devicetree node
represents. Each device driver checks for specific compatible
property values to find the devicetree nodes that represent
resources that the driver should manage.
The recommended format is "vendor,device", The "vendor" part is
an abbreviated name of the vendor. The "device" is usually from
the datasheet.
The compatible property can have multiple values, ordered from
most- to least-specific. Having additional values is useful when the
device is a specific instance of a more general family, to allow the
system to match the most specific driver available.
For details, see "2.3.1 compatible" in Devicetree Specification v0.4.
This property is required. See Important properties for more information. |
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Optional names given to each register block in the "reg" property.
For example:
/ {
soc {
#address-cells = <1>;
#size-cells = <1>;
uart@1000 {
reg = <0x1000 0x2000>, <0x3000 0x4000>;
reg-names = "foo", "bar";
};
};
};
The uart@1000 node has two register blocks:
- one with base address 0x1000, size 0x2000, and name "foo"
- another with base address 0x3000, size 0x4000, and name "bar"
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Information used to define a mapping (or translation) between the address
space of a bus (the "child address space") and the address space of the
bus node's parent (the "parent address space").
The "ranges" property is typically empty, or a sequence of triplets
(child bus address, parent bus address, length).
If the "ranges" property is empty, it specifies that the parent and child
address spaces are identical and no address translation is required.
If the "ranges" property is not present in a bus node, it is assumed that
no mapping exists between children of the node and the parent address space.
For details, see "2.3.8 ranges" in Devicetree Specification v0.4.
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Extended interrupt specifier for device, used as an alternative to
the "interrupts" property.
For details, see "2.4 Interrupts and Interrupt Mapping" in
Devicetree Specification v0.4.
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If present, this refers to the node which handles interrupts generated
by this device.
For details, see "2.4 Interrupts and Interrupt Mapping" in
Devicetree Specification v0.4.
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Human readable string describing the device. Use of this property is
deprecated except as needed on a case-by-case basis.
For details, see "4.1.2 Miscellaneous Properties" in Devicetree
Specification v0.4.
See Important properties for more information. |
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This property encodes the number of <u32> cells used by address fields
in "reg" properties in this node's children.
For details, see "2.3.5 #address-cells and #size-cells" in Devicetree
Specification v0.4.
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This property encodes the number of <u32> cells used by size fields in
"reg" properties in this node's children.
For details, see "2.3.5 #address-cells and #size-cells" in Devicetree
Specification v0.4.
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Indicates that the device is capable of coherent DMA operations.
For details, see "2.3.10 dma-coherent" in Devicetree Specification v0.4.
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DMA channel specifiers relevant to the device.
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Optional names given to the DMA channel specifiers in the "dmas" property.
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The dma-ranges provides a means of defining a mapping or translation between the
physical address space of the bus and the physical address space of the parent of the bus.
For details, see "2.3.9 dma-ranges" in Devicetree Specification v0.4.
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IO channel specifiers relevant to the device.
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Optional names given to the IO channel specifiers in the "io-channels" property.
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Mailbox / IPM channel specifiers relevant to the device.
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Optional names given to the mbox specifiers in the "mboxes" property.
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Power domain specifiers relevant to the device.
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Optional names given to the power domain specifiers in the "power-domains" property.
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Number of cells in power-domains property
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HW spinlock id relevant to the device.
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Optional names given to the hwlock specifiers in the "hwlocks" property.
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Do not initialize device automatically on boot. Device should be manually
initialized using device_init().
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Property to identify that a device can be used as wake up source.
When this property is provided a specific flag is set into the
device that tells the system that the device is capable of
wake up the system.
Wake up capable devices are disabled (interruptions will not wake up
the system) by default but they can be enabled at runtime if necessary.
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Automatically configure the device for runtime power management after the
init function runs.
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List of power states that will disable this device power.
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