[PATCH v3 0/4] tty: serial: uartlite: Disable changing fixed parameters

The uartlite device is a "soft" device and certain parameters (such as
data bits, parity, and baud) are configured at synthesis time, and
cannot be discovered at runtime. Fortunately, bindings for this device
typically include some of these parameters (especially baud rate).
Instead of silently letting Linux's termios drift away from what the
hardware is actually doing, make the termios reflect the hardware, and
prevent them from being changed. With this series applied, the user
recieves an error message when they try to change these parameters:

    # stty parity
    stty: standard input: cannot perform all requested operations

Changes in v3:
- Use unevaluatedProperties: false instead of additionalProperties
- Removed defaults for required properties
- Remove warnings about unsupported termios
- Set defaults for xlnx,data-bits and xlnx,use-parity

Changes in v2:
- Compare the baud computed with uart_get_baud_rate to pdata->baud,
  instead of just checking c_cflag. This will catch anything that messes
  with ispeed and ospeed.
- Don't bother trying to set the initial termios. Instead, just skip
  warning if old is NULL.
- Because we no longer use uart_set_options, just convert the devicetree
  properties directly to clflags.

Sean Anderson (4):
  dt-bindings: serial: uartlite: Convert to json-schema
  dt-bindings: serial: uartlite: Add properties for synthesis-time
    parameters
  sh: j2: Update uartlite binding with data and parity properties
  tty: serial: uartlite: Prevent changing fixed parameters

 .../bindings/serial/xlnx,opb-uartlite.txt     | 23 -----
 .../bindings/serial/xlnx,opb-uartlite.yaml    | 90 ++++++++++++++++++
 arch/sh/boot/dts/j2_mimas_v2.dts              |  2 +
 drivers/tty/serial/uartlite.c                 | 91 ++++++++++++++++---
 4 files changed, 172 insertions(+), 34 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.txt
 create mode 100644 Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml

-- 
2.25.1

This converts the existing documentation for the uartlite binding to
json-schema.

Signed-off-by: Sean Anderson <redacted>
Reviewed-by: Rob Herring <robh@kernel.org>
---

Changes in v3:
- Use unevaluatedProperties: false instead of additionalProperties

 .../bindings/serial/xlnx,opb-uartlite.txt     | 23 --------
 .../bindings/serial/xlnx,opb-uartlite.yaml    | 53 +++++++++++++++++++
 2 files changed, 53 insertions(+), 23 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.txt
 create mode 100644 Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml

diff --git a/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.txt b/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.txt
deleted file mode 100644
index c37deb44dead..000000000000
--- a/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.txt
+++ /dev/null

@@ -1,23 +0,0 @@
-Xilinx Axi Uartlite controller Device Tree Bindings
----------------------------------------------------------
-
-Required properties:
-- compatible		: Can be either of
-				"xlnx,xps-uartlite-1.00.a"
-				"xlnx,opb-uartlite-1.00.b"
-- reg			: Physical base address and size of the Axi Uartlite
-			  registers map.
-- interrupts		: Should contain the UART controller interrupt.
-
-Optional properties:
-- port-number		: Set Uart port number
-- clock-names		: Should be "s_axi_aclk"
-- clocks		: Input clock specifier. Refer to common clock bindings.
-
-Example:
-serial@800c0000 {
-	compatible = "xlnx,xps-uartlite-1.00.a";
-	reg = <0x0 0x800c0000 0x10000>;
-	interrupts = <0x0 0x6e 0x1>;
-	port-number = <0>;
-};

diff --git a/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml b/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml
new file mode 100644
index 000000000000..0cc94c920b17
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml

@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/xlnx,opb-uartlite.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Xilinx Axi Uartlite
+
+maintainers:
+  - Peter Korsgaard <jacmet@sunsite.dk>
+
+properties:
+  compatible:
+    contains:
+      enum:
+        - xlnx,xps-uartlite-1.00.a
+        - xlnx,opb-uartlite-1.00.b
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  port-number:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: Set Uart port number
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: s_axi_aclk
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+allOf:
+  - $ref: /schemas/serial.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+      serial@800c0000 {
+        compatible = "xlnx,xps-uartlite-1.00.a";
+        reg = <0x800c0000 0x10000>;
+        interrupts = <0x0 0x6e 0x1>;
+        port-number = <0>;
+      };
+...

-- 
2.25.1

The uartlite device is a "soft" device. Many parameters, such as baud
rate, data bits, and the presence of a parity bit are configured before
synthesis and may not be changed (or discovered) at runtime. However, we
must know what these settings are in order to properly calculate the
uart timeout (and to inform the user about the actual baud of the uart).

These properties are present for out-of-tree bindings generated by
Xilinx's tools. However, they are also (mostly) present in in-tree
bindings. I chose current-speed over xlnx,baudrate primarily because it
seemed to be used by more existing bindings. Although these properties
are marked as "required", note that only current-speed is required by
the driver itself. Hopefully, this will allow for an easier transition.

Signed-off-by: Sean Anderson <redacted>
---

Changes in v3:
- Removed defaults for required properties

 .../bindings/serial/xlnx,opb-uartlite.yaml    | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml b/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml
index 0cc94c920b17..b8a2bfe14bed 100644
--- a/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml
+++ b/Documentation/devicetree/bindings/serial/xlnx,opb-uartlite.yaml

@@ -32,13 +32,47 @@ properties:
   clock-names:
     const: s_axi_aclk
 
+  current-speed:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      The fixed baud rate that the device was configured for.
+
+  xlnx,data-bits:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [5, 6, 7, 8]
+    description:
+      The fixed number of data bits that the device was configured for.
+
+  xlnx,use-parity:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [0, 1]
+    description:
+      Whether parity checking was enabled when the device was configured.
+
+  xlnx,odd-parity:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [0, 1]
+    description:
+      Whether odd parity was configured.
+
 required:
   - compatible
   - reg
   - interrupts
+  - current-speed
+  - xlnx,data-bits
+  - xlnx,use-parity
 
 allOf:
   - $ref: /schemas/serial.yaml#
+  - if:
+      properties:
+        xlnx,use-parity:
+          contains:
+            const: 1
+    then:
+      required:
+        - xlnx,odd-parity
 
 unevaluatedProperties: false
 

@@ -49,5 +83,8 @@ examples:
         reg = <0x800c0000 0x10000>;
         interrupts = <0x0 0x6e 0x1>;
         port-number = <0>;
+        current-speed = <115200>;
+        xlnx,data-bits = <8>;
+        xlnx,use-parity = <0>;
       };
 ...

-- 
2.25.1

On Thu, 26 Aug 2021 15:21:52 -0400, Sean Anderson wrote:

The uartlite device is a "soft" device. Many parameters, such as baud
rate, data bits, and the presence of a parity bit are configured before
synthesis and may not be changed (or discovered) at runtime. However, we
must know what these settings are in order to properly calculate the
uart timeout (and to inform the user about the actual baud of the uart).

These properties are present for out-of-tree bindings generated by
Xilinx's tools. However, they are also (mostly) present in in-tree
bindings. I chose current-speed over xlnx,baudrate primarily because it
seemed to be used by more existing bindings. Although these properties
are marked as "required", note that only current-speed is required by
the driver itself. Hopefully, this will allow for an easier transition.

Signed-off-by: Sean Anderson <redacted>
---

Changes in v3:
- Removed defaults for required properties

 .../bindings/serial/xlnx,opb-uartlite.yaml    | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)

Reviewed-by: Rob Herring <robh@kernel.org>