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authorWolfram Sang <wsa+renesas@sang-engineering.com>2015-12-08 10:37:46 +0100
committerWolfram Sang <wsa@the-dreams.de>2015-12-14 10:51:07 +0100
commite1dba01ca620bb0b3864d5237c1c597d9e012ebf (patch)
tree44b4a1e51fbb14fc803f2cbd18a13c0509eda207
parenti2c: document generic DT bindings for timing parameters (diff)
downloadlinux-e1dba01ca620bb0b3864d5237c1c597d9e012ebf.tar.xz
linux-e1dba01ca620bb0b3864d5237c1c597d9e012ebf.zip
i2c: add generic routine to parse DT for timing information
Inspired from the i2c-rk3x driver (thanks guys!) but refactored and extended. See built-in docs for further information. Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
-rw-r--r--drivers/i2c/i2c-core.c53
-rw-r--r--include/linux/i2c.h18
2 files changed, 71 insertions, 0 deletions
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index ba8eb087f224..b34c412bd2c2 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -53,6 +53,7 @@
#include <linux/jump_label.h>
#include <asm/uaccess.h>
#include <linux/err.h>
+#include <linux/property.h>
#include "i2c-core.h"
@@ -1438,6 +1439,58 @@ static void of_i2c_register_devices(struct i2c_adapter *adap)
}
}
+/**
+ * i2c_parse_fw_timings - get I2C related timing parameters from firmware
+ * @dev: The device to scan for I2C timing properties
+ * @t: the i2c_timings struct to be filled with values
+ * @use_defaults: bool to use sane defaults derived from the I2C specification
+ * when properties are not found, otherwise use 0
+ *
+ * Scan the device for the generic I2C properties describing timing parameters
+ * for the signal and fill the given struct with the results. If a property was
+ * not found and use_defaults was true, then maximum timings are assumed which
+ * are derived from the I2C specification. If use_defaults is not used, the
+ * results will be 0, so drivers can apply their own defaults later. The latter
+ * is mainly intended for avoiding regressions of existing drivers which want
+ * to switch to this function. New drivers almost always should use the defaults.
+ */
+
+void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults)
+{
+ int ret;
+
+ memset(t, 0, sizeof(*t));
+
+ ret = device_property_read_u32(dev, "clock-frequency", &t->bus_freq_hz);
+ if (ret && use_defaults)
+ t->bus_freq_hz = 100000;
+
+ ret = device_property_read_u32(dev, "i2c-scl-rising-time-ns", &t->scl_rise_ns);
+ if (ret && use_defaults) {
+ if (t->bus_freq_hz <= 100000)
+ t->scl_rise_ns = 1000;
+ else if (t->bus_freq_hz <= 400000)
+ t->scl_rise_ns = 300;
+ else
+ t->scl_rise_ns = 120;
+ }
+
+ ret = device_property_read_u32(dev, "i2c-scl-falling-time-ns", &t->scl_fall_ns);
+ if (ret && use_defaults) {
+ if (t->bus_freq_hz <= 400000)
+ t->scl_fall_ns = 300;
+ else
+ t->scl_fall_ns = 120;
+ }
+
+ device_property_read_u32(dev, "i2c-scl-internal-delay-ns", &t->scl_int_delay_ns);
+
+ ret = device_property_read_u32(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns);
+ if (ret && use_defaults)
+ t->sda_fall_ns = t->scl_fall_ns;
+}
+EXPORT_SYMBOL_GPL(i2c_parse_fw_timings);
+
static int of_dev_node_match(struct device *dev, void *data)
{
return dev->of_node == data;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 51028f351d13..bc2b19ad9357 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -414,6 +414,22 @@ struct i2c_algorithm {
};
/**
+ * struct i2c_timings - I2C timing information
+ * @bus_freq_hz: the bus frequency in Hz
+ * @scl_rise_ns: time SCL signal takes to rise in ns; t(r) in the I2C specification
+ * @scl_fall_ns: time SCL signal takes to fall in ns; t(f) in the I2C specification
+ * @scl_int_delay_ns: time IP core additionally needs to setup SCL in ns
+ * @sda_fall_ns: time SDA signal takes to fall in ns; t(f) in the I2C specification
+ */
+struct i2c_timings {
+ u32 bus_freq_hz;
+ u32 scl_rise_ns;
+ u32 scl_fall_ns;
+ u32 scl_int_delay_ns;
+ u32 sda_fall_ns;
+};
+
+/**
* 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().
@@ -604,6 +620,7 @@ extern void i2c_clients_command(struct i2c_adapter *adap,
extern struct i2c_adapter *i2c_get_adapter(int nr);
extern void i2c_put_adapter(struct i2c_adapter *adap);
+void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults);
/* Return the functionality mask */
static inline u32 i2c_get_functionality(struct i2c_adapter *adap)
@@ -660,6 +677,7 @@ extern struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
/* must call i2c_put_adapter() when done with returned i2c_adapter device */
struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node);
+
#else
static inline struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)