[PATCH 3/4] spi: Add a DT binding for high impedance turnaround

[PATCH 3/4] spi: Add a DT binding for high impedance turnaround

[Linus Walleij]

Some 3WIRE SPI devices require the host to insert a "high
impedance turnaround" essentially a clock pulse after
switching the one line from output to input.

This is needed to support the TPO TPG110 panel to use
the 3WIRE SPI bindings.

Cc: devicetree@vger.kernel.org
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 Documentation/devicetree/bindings/spi/spi-bus.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
index 1f6e86f787ef..ee08be2894eb 100644
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -70,6 +70,10 @@ All slave nodes can contain the following optional properties:
 - spi-cs-high     - Empty property indicating device requires chip select
 		    active high.
 - spi-3wire       - Empty property indicating device requires 3-wire mode.
+- spi-3wire-high-impedance-turnaround - Empty property indicating that a
+		    3wire host need to insert a high impedance turn-around
+		    clock cycle after turning the one output line into an
+		    input line.
 - spi-lsb-first   - Empty property indicating device requires LSB first mode.
 - spi-tx-bus-width - The bus width (number of data wires) that is used for MOSI.
 		    Defaults to 1 if not present.
-- 
2.17.1

Re: [PATCH 3/4] spi: Add a DT binding for high impedance turnaround

[Geert Uytterhoeven]

Hi Linus,

On Mon, Sep 3, 2018 at 11:51 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> Some 3WIRE SPI devices require the host to insert a "high
> impedance turnaround" essentially a clock pulse after

high-impedance

(English allows both, but since you use "turn-around")

> switching the one line from output to input.
>
> This is needed to support the TPO TPG110 panel to use
> the 3WIRE SPI bindings.
>
> Cc: devicetree@vger.kernel.org
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Thanks for your patch!

> --- a/Documentation/devicetree/bindings/spi/spi-bus.txt
> +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
> @@ -70,6 +70,10 @@ All slave nodes can contain the following optional properties:
>  - spi-cs-high     - Empty property indicating device requires chip select
>                     active high.
>  - spi-3wire       - Empty property indicating device requires 3-wire mode.
> +- spi-3wire-high-impedance-turnaround - Empty property indicating that a
> +                   3wire host need to insert a high impedance turn-around

needs
high-impedance

> +                   clock cycle after turning the one output line into an
> +                   input line.
>  - spi-lsb-first   - Empty property indicating device requires LSB first mode.
>  - spi-tx-bus-width - The bus width (number of data wires) that is used for MOSI.
>                     Defaults to 1 if not present.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds