On Wed, 25 Jan 2017, Peter Griffin wrote:

Hi Lee,

On Tue, 24 Jan 2017, Lee Jones wrote:

quoted

Hardware flow-control capability must be specified at a platform
level in order to inform the ASC driver that the platform is capable
(i.e. are the lines wired up, etc).  STiH4{07,10} devices are indeed
capable, so let's provide the property.

Signed-off-by: Lee Jones <redacted>
---
 arch/arm/boot/dts/stih407-family.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/stih407-family.dtsi b/arch/arm/boot/dts/stih407-family.dtsi
index 9789978..7ada8ea 100644
--- a/arch/arm/boot/dts/stih407-family.dtsi
+++ b/arch/arm/boot/dts/stih407-family.dtsi

@@ -226,7 +226,7 @@
 			pinctrl-0 = <&pinctrl_serial0_flowctrl>;
 			pinctrl-1 = <&pinctrl_serial0>;
 			clocks = <&clk_s_c0_flexgen CLK_EXT2F_A9>;
-
+			st,hw-flow-control;

There is a generic serial binding for this already. As this ST property
hasn't been used upstream, it seems like it would be worth dropping it
and switching to the generic uart-has-rtscts one.

See Documentation/devicetree/bindings/serial/serial.txt

  - uart-has-rtscts: The presence of this property indicates that the
    UART has dedicated lines for RTS/CTS hardware flow control, and that
    they are available for use (wired and enabled by pinmux configuration).
    This depends on both the UART hardware and the board wiring.
    Note that this property is mutually-exclusive with "cts-gpios" and
    "rts-gpios" above.

I've done some digging and I can't see anywhere where
st,hw-flow-control is being used, even in the BSP kernel(s).  It's
also not documented in dt-bindings.  With that in mind, I think it's
probably okay to use the generic binding.

Although, the "Note" at the bottom of the uart-has-rtscts is not
correct in our case, since we handle the case dynamically.

Also you should put this in the board dtsi, as it is board dependent property.
By putting it here you are enabling hw-flow-control for all stih407-family
based boards.

Fair shout.
  
On the B2120 UART0 is hooked up to the Smart Card Reader.
  
Will fix.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
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