| Message ID | 20230602115201.415718-1-matthias.schiffer@ew.tq-group.com |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] spi: dt-bindings: introduce linux,use-rt-queue flag | expand |
On Fri, Jun 02, 2023 at 01:52:00PM +0200, Matthias Schiffer wrote: > We have seen a number of downstream patches that allow enabling the > realtime feature of the SPI subsystem to reduce latency. These were > usually implemented for a specific SPI driver, even though the actual > handling of the rt flag is happening in the generic SPI controller code. > > Introduce a generic linux,use-rt-queue flag that can be used with any > controller driver. The now redundant driver-specific pl022,rt flag is > marked as deprecated. This is clearly OS specific tuning so out of scope for DT...
On Tue, Jun 06, 2023 at 04:37:08PM +0200, Linus Walleij wrote: > On Fri, Jun 2, 2023 at 2:22 PM Mark Brown <broonie@kernel.org> wrote: > > On Fri, Jun 02, 2023 at 01:52:00PM +0200, Matthias Schiffer wrote: > > > > We have seen a number of downstream patches that allow enabling the > > > realtime feature of the SPI subsystem to reduce latency. These were > > > usually implemented for a specific SPI driver, even though the actual > > > handling of the rt flag is happening in the generic SPI controller code. > > > > > > Introduce a generic linux,use-rt-queue flag that can be used with any > > > controller driver. The now redundant driver-specific pl022,rt flag is > > > marked as deprecated. > > > > This is clearly OS specific tuning so out of scope for DT... > > In a sense, but to be fair anything prefixed linux,* is out of scope for DT, > Documentation/devicetree/bindings/input/matrix-keymap.yaml being > the most obvious offender. > > On the other hand I think the DT maintainers said it is basically fine > to use undocumented DT properties for this kind of thing. Having > completely undocumented DT properties might seem evil in another > sense, but I think Apple does nothing but... I don't don't know where you got that impression. I'm fine with them in the sense that I don't look at downstream and anything goes there. Rob
diff --git a/Documentation/devicetree/bindings/spi/spi-controller.yaml b/Documentation/devicetree/bindings/spi/spi-controller.yaml index 524f6fe8c27b4..a24b4ea87443b 100644 --- a/Documentation/devicetree/bindings/spi/spi-controller.yaml +++ b/Documentation/devicetree/bindings/spi/spi-controller.yaml @@ -79,6 +79,12 @@ properties: description: The SPI controller acts as a slave, instead of a master. + linux,use-rt-queue: + $ref: /schemas/types.yaml#/definitions/flag + description: + Indicates that the controller should run the message pump with realtime + priority to minimise the transfer latency on the bus. + slave: type: object diff --git a/Documentation/devicetree/bindings/spi/spi-pl022.yaml b/Documentation/devicetree/bindings/spi/spi-pl022.yaml index 91e540a92fafe..3c43fcc007e1f 100644 --- a/Documentation/devicetree/bindings/spi/spi-pl022.yaml +++ b/Documentation/devicetree/bindings/spi/spi-pl022.yaml @@ -49,8 +49,10 @@ properties: pl022,rt: description: indicates the controller should run the message pump with realtime - priority to minimise the transfer latency on the bus (boolean) + priority to minimise the transfer latency on the bus (deprecated, use the + generic linux,use-rt-queue property) type: boolean + deprecated: true dmas: description:
We have seen a number of downstream patches that allow enabling the realtime feature of the SPI subsystem to reduce latency. These were usually implemented for a specific SPI driver, even though the actual handling of the rt flag is happening in the generic SPI controller code. Introduce a generic linux,use-rt-queue flag that can be used with any controller driver. The now redundant driver-specific pl022,rt flag is marked as deprecated. Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com> --- Documentation/devicetree/bindings/spi/spi-controller.yaml | 6 ++++++ Documentation/devicetree/bindings/spi/spi-pl022.yaml | 4 +++- 2 files changed, 9 insertions(+), 1 deletion(-)