| Message ID | 20220217134835.282389-2-rf@opensource.cirrus.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | ASoC: audio_graph_card2: Support variable slot widths | expand |
On Thu, Feb 17, 2022 at 01:48:34PM +0000, Richard Fitzgerald wrote: > Some audio hardware cannot support a fixed slot width or a slot width > equal to the sample width in all cases. This is usually due either to > limitations of the audio serial port or system clocking restrictions. > > This property allows setting a mapping of sample widths and the > corresponding tdm slot widths. > > Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> > --- > .../devicetree/bindings/sound/audio-graph-port.yaml | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/Documentation/devicetree/bindings/sound/audio-graph-port.yaml b/Documentation/devicetree/bindings/sound/audio-graph-port.yaml > index 476dcb49ece6..420adad49382 100644 > --- a/Documentation/devicetree/bindings/sound/audio-graph-port.yaml > +++ b/Documentation/devicetree/bindings/sound/audio-graph-port.yaml > @@ -71,4 +71,11 @@ patternProperties: > description: CPU to Codec rate channels. > $ref: /schemas/types.yaml#/definitions/uint32 > > + dai-tdm-slot-width-map: > + description: Mapping of sample widths to slot widths. For hardware that > + cannot support a fixed slot width or a slot width equal to sample A variable slot width sounds like a feature, not a limitation. > + width. An array containing one or more pairs of values. Each pair > + of values is a sample_width and the corresponding slot_width. That sounds like a matrix, not an array. N entries of 2 cells each. > + $ref: /schemas/types.yaml#/definitions/uint32-array > + I'd think there are some constraints on the values? Slots should be at least 8 bits, right? A max of 2x32 bits or is there more than stereo within a slot? In any case, it's for sure no where near 2^32 max. Is there a need for specifying where in the slot the data is? Rob
On 24/02/2022 22:10, Rob Herring wrote: > On Thu, Feb 17, 2022 at 01:48:34PM +0000, Richard Fitzgerald wrote: >> Some audio hardware cannot support a fixed slot width or a slot width >> equal to the sample width in all cases. This is usually due either to >> limitations of the audio serial port or system clocking restrictions. >> >> This property allows setting a mapping of sample widths and the >> corresponding tdm slot widths. >> >> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> >> --- >> .../devicetree/bindings/sound/audio-graph-port.yaml | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/sound/audio-graph-port.yaml b/Documentation/devicetree/bindings/sound/audio-graph-port.yaml >> index 476dcb49ece6..420adad49382 100644 >> --- a/Documentation/devicetree/bindings/sound/audio-graph-port.yaml >> +++ b/Documentation/devicetree/bindings/sound/audio-graph-port.yaml >> @@ -71,4 +71,11 @@ patternProperties: >> description: CPU to Codec rate channels. >> $ref: /schemas/types.yaml#/definitions/uint32 >> >> + dai-tdm-slot-width-map: >> + description: Mapping of sample widths to slot widths. For hardware that >> + cannot support a fixed slot width or a slot width equal to sample > > A variable slot width sounds like a feature, not a limitation. > Depends on point of view. Most interfaces allow setting a fixed slot width but in some cases that's not possible so it is more likely to be seen as a limitation. It is however a feature in the sense that it can avoid using higher frequencies that are necessary. >> + width. An array containing one or more pairs of values. Each pair >> + of values is a sample_width and the corresponding slot_width. > > That sounds like a matrix, not an array. N entries of 2 cells each. > >> + $ref: /schemas/types.yaml#/definitions/uint32-array >> + > > I'd think there are some constraints on the values? Slots should be at > least 8 bits, right? A max of 2x32 bits or is there more True. I didn't think it was appropriate for a generic binding to enforce a range when that depends on the exact hardware. But if you want I can enforce a range that's likely to be true for all hardware. > than stereo within a slot? In any case, it's for sure no where near 2^32 > max. One sample per slot. > > Is there a need for specifying where in the slot the data is? I don't believe so, all the protocols I know of have the data bits transmitted first followed by padding. There's no harm adding a reserved field to allow for this info if it is ever needed, but it would be unused at present as there's no kernel API to do this. > > Rob >
On Fri, Feb 25, 2022 at 12:08:00PM +0000, Richard Fitzgerald wrote: > On 24/02/2022 22:10, Rob Herring wrote: > > Is there a need for specifying where in the slot the data is? > I don't believe so, all the protocols I know of have the data bits > transmitted first followed by padding. There's no harm adding a > reserved field to allow for this info if it is ever needed, but it would > be unused at present as there's no kernel API to do this. It's part of the general format for the bus I'd say.
diff --git a/Documentation/devicetree/bindings/sound/audio-graph-port.yaml b/Documentation/devicetree/bindings/sound/audio-graph-port.yaml index 476dcb49ece6..420adad49382 100644 --- a/Documentation/devicetree/bindings/sound/audio-graph-port.yaml +++ b/Documentation/devicetree/bindings/sound/audio-graph-port.yaml @@ -71,4 +71,11 @@ patternProperties: description: CPU to Codec rate channels. $ref: /schemas/types.yaml#/definitions/uint32 + dai-tdm-slot-width-map: + description: Mapping of sample widths to slot widths. For hardware that + cannot support a fixed slot width or a slot width equal to sample + width. An array containing one or more pairs of values. Each pair + of values is a sample_width and the corresponding slot_width. + $ref: /schemas/types.yaml#/definitions/uint32-array + additionalProperties: true
Some audio hardware cannot support a fixed slot width or a slot width equal to the sample width in all cases. This is usually due either to limitations of the audio serial port or system clocking restrictions. This property allows setting a mapping of sample widths and the corresponding tdm slot widths. Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> --- .../devicetree/bindings/sound/audio-graph-port.yaml | 7 +++++++ 1 file changed, 7 insertions(+)