-----Original Message-----
From: Mark Rutland [mailto:mark.rutland at arm.com]
Sent: Friday, August 15, 2014 4:16 PM
To: Sharma Bhupesh-B45370
Cc: devicetree-discuss at lists.ozlabs.org; Catalin Marinas; arnd at arndb.de;
Will Deacon; Yoder Stuart-B08248; grant.likely at secretlab.ca; Basu Arnab-
B45036; linux-arm-kernel at lists.infradead.org
Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL NS16550A
UART

On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote:

quoted

This patch addss the device-tree documentation for Freescale's
NS16550 UART (also called DUART).

There is a specific errata fix required in FSL NS16550 UART which
ensures that an random interrupt storm is not observed when a break is
provided as an input to the UART.

Should this not go in
Documentation/devicetree/bindings/serial/of-serial.txt as with other
NS16550A variations?

The only code for handling this string seems to live in
arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring that out
into common code? Or is the erratum not applicable to the revision used in
your ARMv8 SoC?

The FSL specific 8250 (or NS16550A0 driver) at path drivers/tty/serial/8250/8250_fsl.c 
uses this string and provides the code to handle the erratum (see [1])

The NS16550 UART present on our SoC and the corresponding simulator model has this erratum and
hence the specific way in which IRQ are handled (fsl8250_handle_irq) by the driver (in [1])
is applicable here as well.

[1] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/tty/serial/8250/8250_fsl.c?id=refs/tags/next-20140815

Regards,
Bhupesh

Thanks,
Mark.

quoted

Signed-off-by: Bhupesh Sharma <redacted>
---
 .../devicetree/bindings/serial/fsl-ns16550.txt     |   24

++++++++++++++++++++

quoted

 1 file changed, 24 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/serial/fsl-ns16550.txt

diff --git a/Documentation/devicetree/bindings/serial/fsl-ns16550.txt

b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt
new file mode 100644
index 0000000..9926e10

--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt

@@ -0,0 +1,24 @@
+* Freescale DUART is very similar to the PC16552D (and to a
+  pair of NS16550A), albeit with some nonstandard behavior such as
+  erratum A-004737 (relating to incorrect BRK handling).
+
+- compatible: "fsl,ns16550"
+
+  Represents a single port that is compatible with the DUART found
+ on many Freescale chips (examples include mpc8349, mpc8548,
+ mpc8641d, p4080 and ls2085a).
+
+- reg: The base address of the UART register bank.
+
+- interrupts: A single interrupt specifier.
+
+- clock-frequency = Input clock to the baud rate divider.
+
+Example:
+	serial1: serial at 21c4600 {
+		compatible = "fsl,ns16550", "ns16550a";
+		reg = <0x0 0x21c4600 0x0 0x100>;
+		clock-frequency = <0>;
+		interrupts = <0 32 0x1>;
+	};
+
--

1.7.9.5



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