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

Message ID 20230921-rtc-7301-regwidth-v1-2-1900556181bf@linaro.org
State Superseded
Headers show
Series Support byte access in the RTC7301 driver | expand

Commit Message

Linus Walleij Sept. 21, 2023, 8:27 p.m. UTC 
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.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/rtc/rtc-r7301.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

Comments

Alexandre Belloni Sept. 22, 2023, 10:07 p.m. UTC | #1 
Hi,

On 21/09/2023 22:27:43+0200, Linus Walleij wrote:
> diff --git a/drivers/rtc/rtc-r7301.c b/drivers/rtc/rtc-r7301.c
> index 5dbaeb7af648..843e16966b65 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 consequitive bytes.

Shouldn't that be consecutive?
diff mbox series

Patch

diff --git a/drivers/rtc/rtc-r7301.c b/drivers/rtc/rtc-r7301.c
index 5dbaeb7af648..843e16966b65 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 consequitive 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 +380,22 @@  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:
+	default:
+		mapconf = &rtc7301_regmap_32_config;
+	}
+
 	priv->regmap = devm_regmap_init_mmio(&dev->dev, regs,
-					     &rtc7301_regmap_config);
+					     mapconf);
 	if (IS_ERR(priv->regmap))
 		return PTR_ERR(priv->regmap);