On Wed, Oct 5, 2016 at 9:09 AM, Gerald Baeza [off-list ref] wrote:

On 09/23/2016 05:29 PM, Rob Herring wrote:

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On Thu, Sep 15, 2016 at 06:42:34PM +0200, Alexandre TORGUE wrote:

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This adds documentation of device tree bindings for the
STM32 USART

Please make your subject prefixes consistent and drop "DOCUMENTATION".

Ok, thanks

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Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Alexandre TORGUE <redacted>

diff --git a/Documentation/devicetree/bindings/serial/st,stm32-usart.txt

b/Documentation/devicetree/bindings/serial/st,stm32-usart.txt
new file mode 100644
index 0000000..75b1400

--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/st,stm32-usart.txt

@@ -0,0 +1,34 @@
+* STMicroelectronics STM32 USART
+
+Required properties:
+- compatible: Can be either "st,stm32-usart", "st,stm32-uart",
+"st,stm32f7-usart" or "st,stm32f7-uart" depending on whether
+the device supports synchronous mode and is compatible with
+stm32(f4) or stm32f7.

Why not put f4 in the compatible string. stm32 is too generic.

The initial binding is not in current kernel so it has been put in this
serie as PATCH 07/11. It will be squashed with this one, as you requested.

But the driver tty/serial/stm32-usart.c was already upstreamed and it
already mentions the "st,stm32-usart" and "st,stm32-uart" for stm32f4 so I
kept this as it for backward compatibility for those who already use the
driver.

I do not have the history to explain this inconsistency but can you confirm
that keeping the existing compatible values from the driver is the good
approach please?

Yes, keep it as it. Please reformat 1 valid combination per line.

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What determines sync mode or not? If it is IP configuration fixed in the
design, then this is fine. If it is user choice or board dependent, then
use a separate property.

This is IP configuration fixed in the design, indeed.

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+- reg: The address and length of the peripheral registers space
+- interrupts: The interrupt line of the USART instance
+- clocks: The input clock of the USART instance
+
+Optional properties:
+- pinctrl: The reference on the pins configuration
+- st,hw-flow-ctrl: bool flag to enable hardware flow control.
+
+Examples:
+usart4: serial at 40004c00 {
+       compatible = "st,stm32-uart";
+       reg = <0x40004c00 0x400>;
+       interrupts = <52>;
+       clocks = <&clk_pclk1>;
+       pinctrl-names = "default";
+       pinctrl-0 = <&pinctrl_usart4>;
+};
+
+usart2: serial at 40004400 {
+       compatible = "st,stm32-usart", "st,stm32-uart";

What are valid combinations? usart is sync only, not sync and async?

usart (sync and async) is a superset of uart (async).
But the current driver does not use the synchronous mode, so the distinction
is just here to be consistent with the reference manual instances naming (so
configuration).

Okay, but this point is not clear in the compatible text. The
description should allow me to validate the example or a dts file.

Rob