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Date: Thu, 14 Jan 2010 20:32:35 +0900
From: Paul Mundt <lethal@...ux-sh.org>
To: Alessandro Zummo <a.zummo@...ertech.it>,
Dale Farnsworth <dale@...nsworth.org>
Cc: rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: [PATCH] rtc: rtc-max6900: SMBus support.
The current rtc-max6900 driver only supports getting and setting the time
through bursting, which requires a controller capable of such. As
bursting is merely an optimization, we can also opt for the non-burst
fallback path that pokes at the date/time registers individually.
By opting for the fallback solution, it's possible to fully support the
RTC on controllers that only implement I2C_FUNC_SMBUS_BYTE_DATA instead
of requiring master transfers via I2C_FUNC_I2C.
This was tested with an I2C_FUNC_SMBUS_BYTE_DATA controller with a MAX6909
attached. Currently only a subset of the MAX6909 functionality is supported,
patches to extend the current driver to be forthcoming.
There are no functional changes for I2C_FUNC_I2C controllers.
Signed-off-by: Paul Mundt <lethal@...ux-sh.org>
---
drivers/rtc/Kconfig | 4 +-
drivers/rtc/rtc-max6900.c | 83 ++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 79 insertions(+), 8 deletions(-)
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 8167e9e..1f74b46 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -167,10 +167,10 @@ config RTC_DRV_DS1672
will be called rtc-ds1672.
config RTC_DRV_MAX6900
- tristate "Maxim MAX6900"
+ tristate "Maxim MAX6900/MAX6909"
help
If you say yes here you will get support for the
- Maxim MAX6900 I2C RTC chip.
+ Maxim MAX6900 and MAX6909 I2C RTC chips.
This driver can also be built as a module. If so, the module
will be called rtc-max6900.
diff --git a/drivers/rtc/rtc-max6900.c b/drivers/rtc/rtc-max6900.c
index a4f6665..5e0c289 100644
--- a/drivers/rtc/rtc-max6900.c
+++ b/drivers/rtc/rtc-max6900.c
@@ -1,8 +1,10 @@
/*
- * rtc class driver for the Maxim MAX6900 chip
+ * rtc class driver for the Maxim MAX6900/MAX6909 chip
*
* Author: Dale Farnsworth <dale@...nsworth.org>
*
+ * SMBus support by Paul Mundt.
+ *
* based on previously existing rtc class drivers
*
* 2007 (c) MontaVista, Software, Inc. This file is licensed under
@@ -17,7 +19,7 @@
#include <linux/rtc.h>
#include <linux/delay.h>
-#define DRV_VERSION "0.2"
+#define DRV_VERSION "0.3"
/*
* register indices
@@ -39,6 +41,12 @@
#define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */
/*
+ * index to command wrappers
+ */
+#define MAX6900_REG_WRITE(reg) (0x80 + ((reg) * sizeof(u16)))
+#define MAX6900_REG_READ(reg) (0x81 + ((reg) * sizeof(u16)))
+
+/*
* register read/write commands
*/
#define MAX6900_REG_CONTROL_WRITE 0x8e
@@ -52,7 +60,9 @@
static struct i2c_driver max6900_driver;
-static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
+static unsigned int smbus_mode; /* disabled by default, prefer bursting */
+
+static int max6900_i2c_burst_read(struct i2c_client *client, u8 *buf)
{
u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
@@ -92,7 +102,7 @@ static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
return 0;
}
-static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
+static int max6900_i2c_burst_write(struct i2c_client *client, u8 const *buf)
{
u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
struct i2c_msg century_msgs[1] = {
@@ -141,6 +151,58 @@ static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
return -EIO;
}
+static int max6900_i2c_smbus_read(struct i2c_client *client, u8 *buf)
+{
+ int rc = 0, i;
+
+ for (i = 0; i < MAX6900_REG_LEN; i++) {
+ rc = i2c_smbus_read_byte_data(client, MAX6900_REG_READ(i));
+ if (rc < 0) {
+ dev_err(&client->dev, "%s: register read failed\n",
+ __func__);
+ return rc;
+ }
+ buf[i] = rc;
+ }
+
+ return 0;
+}
+
+static int max6900_i2c_smbus_write(struct i2c_client *client, u8 const *buf)
+{
+ int rc = 0, i;
+
+ for (i = 0; i < MAX6900_REG_LEN; i++)
+ rc |= i2c_smbus_write_byte_data(client,
+ MAX6900_REG_WRITE(i), buf[i]);
+
+ if (rc < 0) {
+ dev_err(&client->dev, "%s: register write failed\n",
+ __func__);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static inline int
+max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
+{
+ if (smbus_mode)
+ return max6900_i2c_smbus_read(client, buf);
+
+ return max6900_i2c_burst_read(client, buf);
+}
+
+static inline int
+max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
+{
+ if (smbus_mode)
+ return max6900_i2c_smbus_write(client, buf);
+
+ return max6900_i2c_burst_write(client, buf);
+}
+
static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
{
int rc;
@@ -232,8 +294,17 @@ max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
struct rtc_device *rtc;
- if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
- return -ENODEV;
+ /*
+ * Prefer burst mode if there's a fully functional I2C adapter to
+ * work with, otherwise scrape by with SMBus.
+ */
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+ if (i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_BYTE_DATA))
+ smbus_mode = 1;
+ else
+ return -ENODEV;
+ }
dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
--
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