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rtc: rtc7301: Support byte-addressed IO

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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>
Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>
Link: https://lore.kernel.org/r/20231010-rtc-7301-regwidth-v3-2-ade586b62794@linaro.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Linus Walleij 2023-10-10 21:42:12 +02:00 committed by Alexandre Belloni
parent 5ded578a18
commit 8c767e9c1e
1 changed files with 33 additions and 2 deletions
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35
drivers/rtc/rtc-r7301.c
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@ -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);