[PATCH v3 0/2] Support byte access in the RTC7301 driver

[PATCH v3 0/2] Support byte access in the RTC7301 driver

[Linus Walleij]

This augments the Epson RTC7301 driver so that is supports
both 8bit byte and 32bit word access.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
Changes in v3:
- Use a default in the binding to encode 32bit (4 bytes) reg width
  as default.
- Collect Rob's ACK.
- Link to v2: https://lore.kernel.org/r/20231007-rtc-7301-regwidth-v2-0-c913aa95f666@linaro.org

Changes in v2:
- Specify that the reg-io-width default is 4 if not specified in the
  device tree.
- Fix spelling in driver comment.
- Print error and exit if an invalid width is specified.
- Link to v1: https://lore.kernel.org/r/20230921-rtc-7301-regwidth-v1-0-1900556181bf@linaro.org

---
Linus Walleij (2):
      rtc: rtc7301: Rewrite bindings in schema
      rtc: rtc7301: Support byte-addressed IO

 .../devicetree/bindings/rtc/epson,rtc7301.txt      | 16 -------
 .../devicetree/bindings/rtc/epson,rtc7301.yaml     | 51 ++++++++++++++++++++++
 drivers/rtc/rtc-r7301.c                            | 35 ++++++++++++++-
 3 files changed, 84 insertions(+), 18 deletions(-)
---
base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
change-id: 20230921-rtc-7301-regwidth-18ba1e3d0edb

Best regards,
-- 
Linus Walleij <linus.walleij@linaro.org>

[PATCH v3 1/2] rtc: rtc7301: Rewrite bindings in schema

[Linus Walleij]

This rewrites the Epson RTC7301 bindings to use YAML schema,
and adds a property for "reg-io-width" as used in several
other bindings to account for different register strides.

The USRobotics USR8200 uses the byte IO width.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 .../devicetree/bindings/rtc/epson,rtc7301.txt      | 16 -------
 .../devicetree/bindings/rtc/epson,rtc7301.yaml     | 51 ++++++++++++++++++++++
 2 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/Documentation/devicetree/bindings/rtc/epson,rtc7301.txt b/Documentation/devicetree/bindings/rtc/epson,rtc7301.txt
deleted file mode 100644
index 5f9df3f1467c..000000000000
--- a/Documentation/devicetree/bindings/rtc/epson,rtc7301.txt
+++ /dev/null
@@ -1,16 +0,0 @@
-EPSON TOYOCOM RTC-7301SF/DG
-
-Required properties:
-
-- compatible: Should be "epson,rtc7301sf" or "epson,rtc7301dg"
-- reg: Specifies base physical address and size of the registers.
-- interrupts: A single interrupt specifier.
-
-Example:
-
-rtc: rtc@44a00000 {
-	compatible = "epson,rtc7301dg";
-	reg = <0x44a00000 0x10000>;
-	interrupt-parent = <&axi_intc_0>;
-	interrupts = <3 2>;
-};
diff --git a/Documentation/devicetree/bindings/rtc/epson,rtc7301.yaml b/Documentation/devicetree/bindings/rtc/epson,rtc7301.yaml
new file mode 100644
index 000000000000..bdb5cadb31cc
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/epson,rtc7301.yaml
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/epson,rtc7301.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Epson Toyocom RTC-7301SF/DG
+
+description:
+  The only difference between the two variants is the packaging.
+  The DG variant is a DIL package, and the SF variant is a flat
+  package.
+
+maintainers:
+  - Akinobu Mita <akinobu.mita@gmail.com>
+
+properties:
+  compatible:
+    enum:
+      - epson,rtc7301dg
+      - epson,rtc7301sf
+
+  reg:
+    maxItems: 1
+
+  reg-io-width:
+    description:
+      The size (in bytes) of the IO accesses that should be performed
+      on the device.
+    enum: [1, 4]
+    default: 4
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    rtc: rtc@44a00000 {
+        compatible = "epson,rtc7301dg";
+        reg = <0x44a00000 0x10000>;
+        reg-io-width = <4>;
+        interrupt-parent = <&axi_intc_0>;
+        interrupts = <3 2>;
+    };

-- 
2.41.0

[PATCH v3 2/2] rtc: rtc7301: Support byte-addressed IO

[Linus Walleij]

The old RTC7301 driver in OpenWrt used byte access, but the
current mainline Linux driver uses 32bit word access.

Make this configurable using device properties using the
standard property "reg-io-width" in e.g. device tree.

This is needed for the USRobotics USR8200 which has the
chip connected using byte accesses.

Debugging and testing by Howard Harte.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/rtc/rtc-r7301.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-r7301.c b/drivers/rtc/rtc-r7301.c
index 5dbaeb7af648..ef913cf8593f 100644
--- a/drivers/rtc/rtc-r7301.c
+++ b/drivers/rtc/rtc-r7301.c
@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/delay.h>
+#include <linux/property.h>
 #include <linux/regmap.h>
 #include <linux/platform_device.h>
 #include <linux/rtc.h>
@@ -55,12 +56,23 @@ struct rtc7301_priv {
 	u8 bank;
 };
 
-static const struct regmap_config rtc7301_regmap_config = {
+/*
+ * When the device is memory-mapped, some platforms pack the registers into
+ * 32-bit access using the lower 8 bits at each 4-byte stride, while others
+ * expose them as simply consecutive bytes.
+ */
+static const struct regmap_config rtc7301_regmap_32_config = {
 	.reg_bits = 32,
 	.val_bits = 8,
 	.reg_stride = 4,
 };
 
+static const struct regmap_config rtc7301_regmap_8_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.reg_stride = 1,
+};
+
 static u8 rtc7301_read(struct rtc7301_priv *priv, unsigned int reg)
 {
 	int reg_stride = regmap_get_reg_stride(priv->regmap);
@@ -356,7 +368,9 @@ static int __init rtc7301_rtc_probe(struct platform_device *dev)
 	void __iomem *regs;
 	struct rtc7301_priv *priv;
 	struct rtc_device *rtc;
+	static const struct regmap_config *mapconf;
 	int ret;
+	u32 val;
 
 	priv = devm_kzalloc(&dev->dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -366,8 +380,25 @@ static int __init rtc7301_rtc_probe(struct platform_device *dev)
 	if (IS_ERR(regs))
 		return PTR_ERR(regs);
 
+	ret = device_property_read_u32(&dev->dev, "reg-io-width", &val);
+	if (ret)
+		/* Default to 32bit accesses */
+		val = 4;
+
+	switch (val) {
+	case 1:
+		mapconf = &rtc7301_regmap_8_config;
+		break;
+	case 4:
+		mapconf = &rtc7301_regmap_32_config;
+		break;
+	default:
+		dev_err(&dev->dev, "invalid reg-io-width %d\n", val);
+		return -EINVAL;
+	}
+
 	priv->regmap = devm_regmap_init_mmio(&dev->dev, regs,
-					     &rtc7301_regmap_config);
+					     mapconf);
 	if (IS_ERR(priv->regmap))
 		return PTR_ERR(priv->regmap);
 

-- 
2.41.0

Re: [PATCH v3 0/2] Support byte access in the RTC7301 driver

[Akinobu Mita]

2023年10月11日(水) 4:42 Linus Walleij <linus.walleij@linaro.org>:
>
> This augments the Epson RTC7301 driver so that is supports
> both 8bit byte and 32bit word access.

I don't have access to that device anymore, but I think it's a good change.

Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>

Re: [PATCH v3 0/2] Support byte access in the RTC7301 driver

[Alexandre Belloni]

On Tue, 10 Oct 2023 21:42:10 +0200, Linus Walleij wrote:
> This augments the Epson RTC7301 driver so that is supports
> both 8bit byte and 32bit word access.
> 
> 

Applied, thanks!

[1/2] rtc: rtc7301: Rewrite bindings in schema
      commit: 5ded578a18c9515c2c0e1cd148ca42133bbcf055
[2/2] rtc: rtc7301: Support byte-addressed IO
      commit: 8c767e9c1ef40c9fa73276df801251cef895b569

Best regards,

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com