Re: [PATCH v5 15/17] dt-bindings: qca7000: append UART interface to binding
From: Michael Heimpold <hidden>
Date: 2017-05-11 19:12:33
Also in:
linux-devicetree, linux-serial, lkml
Hi, Am Mittwoch, 10. Mai 2017, 10:53:26 CEST schrieb Stefan Wahren:
quoted hunk ↗ jump to hunk
This merges the serdev binding for the QCA7000 UART driver (Ethernet over UART) into the existing document. Signed-off-by: Stefan Wahren <redacted> --- .../devicetree/bindings/net/qca-qca7000.txt | 32 ++++++++++++++++++++++ 1 file changed, 32 insertions(+)diff --git a/Documentation/devicetree/bindings/net/qca-qca7000.txtb/Documentation/devicetree/bindings/net/qca-qca7000.txt index a37f656..08364c3 100644--- a/Documentation/devicetree/bindings/net/qca-qca7000.txt +++ b/Documentation/devicetree/bindings/net/qca-qca7000.txt@@ -54,3 +54,35 @@ ssp2: spi@80014000 { local-mac-address = [ A0 B0 C0 D0 E0 F0 ]; }; }; + +(b) Ethernet over UART + +In order to use the QCA7000 as UART slave it must be defined as a child ofa +UART master in the device tree. It is possible to preconfigure the UART +settings of the QCA7000 firmware, but it's not possible to change them during +runtime. + +Required properties: +- compatible : Should be "qca,qca7000-uart"
I already discussed this with Stefan off-list a little bit, but I would like to bring this to a broader audience: I'm not sure whether the compatible should contain the "-uart" suffix, because the hardware chip is the very same QCA7000 chip which can also be used with SPI protocol. The only difference is the loaded firmware within the chip which can either speak SPI or UART protocol (but not both at the same time - due to shared pins). So the hardware design decides which interface type is used. At the moment, this patch series adds a dedicated driver for the UART protocol, in parallel to the existing SPI driver. So a different compatible string is needed here to match against the new driver. An alternative approach would be to re-use the existing compatible string "qca,qca7000" for both, the SPI and UART protocol, because a "smarter" (combined) driver would detect which protocol to use. For example the driver could check for spi-cpha and/or spi-cpol which are required for SPI protocol: if these exists the driver could assume that SPI must be used, if both are missing then UART protocol should be used. (This way it would not be necessary to check whether the node is a child of a SPI or UART master node - but maybe this is even easier - I don't know) Or in shorter words: my concern is that while "qca7000-uart" describes the hardware, it's too closely coupled to the driver implementation. Having some feedback of the experts would be nice :-) Thanks, Michael
+
+Optional properties:
+- local-mac-address : see ./ethernet.txt
+- current-speed : current baud rate of QCA7000 which defaults to 115200
+ if absent, see also ../serial/slave-device.txt
+
+UART Example:
+
+/* Freescale i.MX28 UART */
+auart0: serial@8006a000 {
+ compatible = "fsl,imx28-auart", "fsl,imx23-auart";
+ reg = <0x8006a000 0x2000>;
+ pinctrl-names = "default";
+ pinctrl-0 = <&auart0_2pins_a>;
+ status = "okay";
+
+ qca7000: ethernet {
+ compatible = "qca,qca7000-uart";
+ local-mac-address = [ A0 B0 C0 D0 E0 F0 ];
+ current-speed = <38400>;
+ };
+};-- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html