[PATCH 1/4] i2c: add bus recovery infrastructure
Jan Luebbe
jluebbe at debian.org
Wed Jul 8 06:29:15 PDT 2015
This is based on the code introduced to the kernel in
5f9296ba21b3c395e53dd84e7ff9578f97f24295.
Signed-off-by: Jan Luebbe <jluebbe at debian.org>
---
drivers/i2c/i2c.c | 161 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/i2c/i2c.h | 42 ++++++++++++++
2 files changed, 203 insertions(+)
diff --git a/drivers/i2c/i2c.c b/drivers/i2c/i2c.c
index ebc7e23..e350ac5 100644
--- a/drivers/i2c/i2c.c
+++ b/drivers/i2c/i2c.c
@@ -23,6 +23,7 @@
#include <xfuncs.h>
#include <init.h>
#include <of.h>
+#include <gpio.h>
#include <i2c/i2c.h>
@@ -228,6 +229,133 @@ int i2c_write_reg(struct i2c_client *client, u32 addr, const u8 *buf, u16 count)
}
EXPORT_SYMBOL(i2c_write_reg);
+/* i2c bus recovery routines */
+static int get_scl_gpio_value(struct i2c_adapter *adap)
+{
+ gpio_direction_input(adap->bus_recovery_info->scl_gpio);
+ return gpio_get_value(adap->bus_recovery_info->scl_gpio);
+}
+
+static void set_scl_gpio_value(struct i2c_adapter *adap, int val)
+{
+ if (val)
+ gpio_direction_input(adap->bus_recovery_info->scl_gpio);
+ else
+ gpio_direction_output(adap->bus_recovery_info->scl_gpio, 0);
+}
+
+static int get_sda_gpio_value(struct i2c_adapter *adap)
+{
+ return gpio_get_value(adap->bus_recovery_info->sda_gpio);
+}
+
+static int i2c_get_gpios_for_recovery(struct i2c_adapter *adap)
+{
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+ struct device_d *dev = &adap->dev;
+ int ret = 0;
+
+ ret = gpio_request_one(bri->scl_gpio, GPIOF_IN, "i2c-scl");
+ if (ret) {
+ dev_warn(dev, "Can't get SCL gpio: %d\n", bri->scl_gpio);
+ return ret;
+ }
+
+ if (bri->get_sda) {
+ if (gpio_request_one(bri->sda_gpio, GPIOF_IN, "i2c-sda")) {
+ /* work without SDA polling */
+ dev_warn(dev, "Can't get SDA gpio: %d. Not using SDA polling\n",
+ bri->sda_gpio);
+ bri->get_sda = NULL;
+ }
+ }
+
+ return ret;
+}
+
+static void i2c_put_gpios_for_recovery(struct i2c_adapter *adap)
+{
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+
+ if (bri->get_sda)
+ gpio_free(bri->sda_gpio);
+
+ gpio_free(bri->scl_gpio);
+}
+
+/*
+ * We are generating clock pulses. ndelay() determines durating of clk pulses.
+ * We will generate clock with rate 100 KHz and so duration of both clock levels
+ * is: delay in ns = (10^6 / 100) / 2
+ */
+#define RECOVERY_NDELAY 5000
+#define RECOVERY_CLK_CNT 9
+
+static int i2c_generic_recovery(struct i2c_adapter *adap)
+{
+ struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
+ int i = 0, val = 1, ret = 0;
+
+ if (bri->prepare_recovery)
+ bri->prepare_recovery(adap);
+
+ /*
+ * By this time SCL is high, as we need to give 9 falling-rising edges
+ */
+ while (i++ < RECOVERY_CLK_CNT * 2) {
+ if (val) {
+ /* Break if SDA is high */
+ if (bri->get_sda && bri->get_sda(adap))
+ break;
+ /* SCL shouldn't be low here */
+ if (!bri->get_scl(adap)) {
+ dev_err(&adap->dev,
+ "SCL is stuck low, exit recovery\n");
+ ret = -EBUSY;
+ break;
+ }
+ }
+
+ val = !val;
+ bri->set_scl(adap, val);
+ ndelay(RECOVERY_NDELAY);
+ }
+
+ if (bri->unprepare_recovery)
+ bri->unprepare_recovery(adap);
+
+ return ret;
+}
+
+int i2c_generic_scl_recovery(struct i2c_adapter *adap)
+{
+ adap->bus_recovery_info->set_scl(adap, 1);
+ return i2c_generic_recovery(adap);
+}
+
+int i2c_generic_gpio_recovery(struct i2c_adapter *adap)
+{
+ int ret;
+
+ ret = i2c_get_gpios_for_recovery(adap);
+ if (ret)
+ return ret;
+
+ ret = i2c_generic_recovery(adap);
+ i2c_put_gpios_for_recovery(adap);
+
+ return ret;
+}
+
+int i2c_recover_bus(struct i2c_adapter *adap)
+{
+ if (!adap->bus_recovery_info)
+ return -EOPNOTSUPP;
+
+ dev_dbg(&adap->dev, "Trying i2c bus recovery\n");
+ return adap->bus_recovery_info->recover_bus(adap);
+}
+
/**
* i2c_new_device - instantiate one new I2C device
*
@@ -456,6 +584,39 @@ int i2c_add_numbered_adapter(struct i2c_adapter *adapter)
list_add_tail(&adapter->list, &adapter_list);
+ /* bus recovery specific initialization */
+ if (adapter->bus_recovery_info) {
+ struct i2c_bus_recovery_info *bri = adapter->bus_recovery_info;
+
+ if (!bri->recover_bus) {
+ dev_err(&adapter->dev, "No recover_bus() found, not using recovery\n");
+ adapter->bus_recovery_info = NULL;
+ goto exit_recovery;
+ }
+
+ /* Generic GPIO recovery */
+ if (bri->recover_bus == i2c_generic_gpio_recovery) {
+ if (!gpio_is_valid(bri->scl_gpio)) {
+ dev_err(&adapter->dev, "Invalid SCL gpio, not using recovery\n");
+ adapter->bus_recovery_info = NULL;
+ goto exit_recovery;
+ }
+
+ if (gpio_is_valid(bri->sda_gpio))
+ bri->get_sda = get_sda_gpio_value;
+ else
+ bri->get_sda = NULL;
+
+ bri->get_scl = get_scl_gpio_value;
+ bri->set_scl = set_scl_gpio_value;
+ } else if (!bri->set_scl || !bri->get_scl) {
+ /* Generic SCL recovery */
+ dev_err(&adapter->dev, "No {get|set}_gpio() found, not using recovery\n");
+ adapter->bus_recovery_info = NULL;
+ }
+ }
+exit_recovery:
+
/* populate children from any i2c device tables */
scan_boardinfo(adapter);
diff --git a/include/i2c/i2c.h b/include/i2c/i2c.h
index 4696f43..04de8c9 100644
--- a/include/i2c/i2c.h
+++ b/include/i2c/i2c.h
@@ -19,6 +19,8 @@
#include <driver.h>
#include <linux/types.h>
+struct i2c_adapter;
+
/*
* struct i2c_platform_data - structure of platform data for MXC I2C driver
* @param bitrate Bus speed measured in Hz
@@ -61,6 +63,44 @@ struct i2c_msg {
__u16 len; /**< Number of data bytes in @buf being read from or written to the I2C slave address. */
};
+/**
+ * struct i2c_bus_recovery_info - I2C bus recovery information
+ * @recover_bus: Recover routine. Either pass driver's recover_bus() routine, or
+ * i2c_generic_scl_recovery() or i2c_generic_gpio_recovery().
+ * @get_scl: This gets current value of SCL line. Mandatory for generic SCL
+ * recovery. Used internally for generic GPIO recovery.
+ * @set_scl: This sets/clears SCL line. Mandatory for generic SCL recovery. Used
+ * internally for generic GPIO recovery.
+ * @get_sda: This gets current value of SDA line. Optional for generic SCL
+ * recovery. Used internally, if sda_gpio is a valid GPIO, for generic GPIO
+ * recovery.
+ * @prepare_recovery: This will be called before starting recovery. Platform may
+ * configure padmux here for SDA/SCL line or something else they want.
+ * @unprepare_recovery: This will be called after completing recovery. Platform
+ * may configure padmux here for SDA/SCL line or something else they want.
+ * @scl_gpio: gpio number of the SCL line. Only required for GPIO recovery.
+ * @sda_gpio: gpio number of the SDA line. Only required for GPIO recovery.
+ */
+struct i2c_bus_recovery_info {
+ int (*recover_bus)(struct i2c_adapter *);
+
+ int (*get_scl)(struct i2c_adapter *);
+ void (*set_scl)(struct i2c_adapter *, int val);
+ int (*get_sda)(struct i2c_adapter *);
+
+ void (*prepare_recovery)(struct i2c_adapter *);
+ void (*unprepare_recovery)(struct i2c_adapter *);
+
+ /* gpio recovery */
+ int scl_gpio;
+ int sda_gpio;
+};
+
+int i2c_recover_bus(struct i2c_adapter *adap);
+
+/* Generic recovery routines */
+int i2c_generic_gpio_recovery(struct i2c_adapter *adap);
+int i2c_generic_scl_recovery(struct i2c_adapter *adap);
/**
* i2c_adapter is the structure used to identify a physical i2c bus
@@ -74,6 +114,8 @@ struct i2c_adapter {
struct list_head list;
int retries;
void *algo_data;
+
+ struct i2c_bus_recovery_info *bus_recovery_info;
};
--
2.1.4
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