Merge branch 'linux-linaro-lsk-v4.4-android' of git://git.linaro.org/kernel/linux...

[firefly-linux-kernel-4.4.55.git] / drivers / i2c / i2c-core.c

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index e4587411b44725d41728909c1d8e33b0a228dbdc..eda0126c17f4df24927d608580e220113c60e1f0 100644 (file)
--- 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"
 
@@ -1839,6 +1840,58 @@ void i2c_del_adapter(struct i2c_adapter *adap)
 }
 EXPORT_SYMBOL(i2c_del_adapter);
 
+/**
+ * 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);
+
 /* ------------------------------------------------------------------------- */
 
 int i2c_for_each_dev(void *data, int (*fn)(struct device *, void *))