* [PATCH 3/4] spi: Add a DT binding for high impedance turnaround
[not found] <20180903215035.17265-1-linus.walleij@linaro.org>
@ 2018-09-03 21:50 ` Linus Walleij
2018-09-04 7:39 ` Geert Uytterhoeven
0 siblings, 1 reply; 2+ messages in thread
From: Linus Walleij @ 2018-09-03 21:50 UTC (permalink / raw)
To: Mark Brown, linux-spi, Andrzej Hajda, Lorenzo Bianconi
Cc: linux-gpio, Rob Herring, Linus Walleij, devicetree
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 3/4] spi: Add a DT binding for high impedance turnaround
2018-09-03 21:50 ` [PATCH 3/4] spi: Add a DT binding for high impedance turnaround Linus Walleij
@ 2018-09-04 7:39 ` Geert Uytterhoeven
0 siblings, 0 replies; 2+ messages in thread
From: Geert Uytterhoeven @ 2018-09-04 7:39 UTC (permalink / raw)
To: Linus Walleij
Cc: Mark Brown, linux-spi, Andrzej Hajda, lorenzo.bianconi,
open list:GPIO SUBSYSTEM, Rob Herring,
open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS
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
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2018-09-03 21:50 ` [PATCH 3/4] spi: Add a DT binding for high impedance turnaround Linus Walleij
2018-09-04 7:39 ` Geert Uytterhoeven
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