diff --git a/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt b/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt
index dde6c22ce91a13df20eaab99ebd6dbf684983768..c4fd545720af64c1009ce54c5517dd497f46c881 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt
@@ -21,6 +21,14 @@ Required on RK3066, RK3188 :
Optional properties :
- clock-frequency : SCL frequency to use (in Hz). If omitted, 100kHz is used.
+ - i2c-scl-rising-time-ns : Number of nanoseconds the signal takes to rise
+ (t(r) in I2C specification). If not specified this is assumed to be
+ the maximum the specification allows(1000 ns for Standard-mode,
+ 300 ns for Fast-mode) which might cause slightly slower communication.
+ - i2c-scl-falling-time-ns : Number of nanoseconds the signal takes to fall
+ (t(f) in the I2C specification). If not specified this is assumed to
+ be the maximum the specification allows (300 ns) which might cause
+ slightly slower communication.
Example:
@@ -39,4 +47,7 @@ i2c0: i2c@2002d000 {
clock-names = "i2c";
clocks = <&cru PCLK_I2C0>;
+
+ i2c-scl-rising-time-ns = <800>;
+ i2c-scl-falling-time-ns = <100>;
};
diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index 92462843db663d09b1106468603b1b9eb65243d2..36a92244581429354c2a9448b9bc71ec1980a7d2 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -102,6 +102,8 @@ struct rk3x_i2c {
/* Settings */
unsigned int scl_frequency;
+ unsigned int rise_ns;
+ unsigned int fall_ns;
/* Synchronization & notification */
spinlock_t lock;
@@ -435,6 +437,8 @@ static irqreturn_t rk3x_i2c_irq(int irqno, void *dev_id)
*
* @clk_rate: I2C input clock rate
* @scl_rate: Desired SCL rate
+ * @rise_ns: How many ns it takes for signals to rise.
+ * @fall_ns: How many ns it takes for signals to fall.
* @div_low: Divider output for low
* @div_high: Divider output for high
*
@@ -443,11 +447,14 @@ static irqreturn_t rk3x_i2c_irq(int irqno, void *dev_id)
* too high, we silently use the highest possible rate.
*/
static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate,
+ unsigned long rise_ns, unsigned long fall_ns,
unsigned long *div_low, unsigned long *div_high)
{
- unsigned long min_low_ns, min_high_ns;
- unsigned long max_data_hold_ns;
+ unsigned long spec_min_low_ns, spec_min_high_ns;
+ unsigned long spec_max_data_hold_ns;
unsigned long data_hold_buffer_ns;
+
+ unsigned long min_low_ns, min_high_ns;
unsigned long max_low_ns, min_total_ns;
unsigned long clk_rate_khz, scl_rate_khz;
@@ -469,29 +476,33 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate,
scl_rate = 1000;
/*
- * min_low_ns: The minimum number of ns we need to hold low
- * to meet i2c spec
- * min_high_ns: The minimum number of ns we need to hold high
- * to meet i2c spec
- * max_low_ns: The maximum number of ns we can hold low
- * to meet i2c spec
+ * min_low_ns: The minimum number of ns we need to hold low to
+ * meet I2C specification, should include fall time.
+ * min_high_ns: The minimum number of ns we need to hold high to
+ * meet I2C specification, should include rise time.
+ * max_low_ns: The maximum number of ns we can hold low to meet
+ * I2C specification.
*
- * Note: max_low_ns should be (max data hold time * 2 - buffer)
+ * Note: max_low_ns should be (maximum data hold time * 2 - buffer)
* This is because the i2c host on Rockchip holds the data line
* for half the low time.
*/
if (scl_rate <= 100000) {
- min_low_ns = 4700;
- min_high_ns = 4000;
- max_data_hold_ns = 3450;
+ /* Standard-mode */
+ spec_min_low_ns = 4700;
+ spec_min_high_ns = 4000;
+ spec_max_data_hold_ns = 3450;
data_hold_buffer_ns = 50;
} else {
- min_low_ns = 1300;
- min_high_ns = 600;
- max_data_hold_ns = 900;
+ /* Fast-mode */
+ spec_min_low_ns = 1300;
+ spec_min_high_ns = 600;
+ spec_max_data_hold_ns = 900;
data_hold_buffer_ns = 50;
}
- max_low_ns = max_data_hold_ns * 2 - data_hold_buffer_ns;
+ min_low_ns = spec_min_low_ns + fall_ns;
+ min_high_ns = spec_min_high_ns + rise_ns;
+ max_low_ns = spec_max_data_hold_ns * 2 - data_hold_buffer_ns;
min_total_ns = min_low_ns + min_high_ns;
/* Adjust to avoid overflow */
@@ -510,8 +521,8 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate,
min_div_for_hold = (min_low_div + min_high_div);
/*
- * This is the maximum divider so we don't go over the max.
- * We don't round up here (we round down) since this is a max.
+ * This is the maximum divider so we don't go over the maximum.
+ * We don't round up here (we round down) since this is a maximum.
*/
max_low_div = clk_rate_khz * max_low_ns / (8 * 1000000);
@@ -544,7 +555,7 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate,
ideal_low_div = DIV_ROUND_UP(clk_rate_khz * min_low_ns,
scl_rate_khz * 8 * min_total_ns);
- /* Don't allow it to go over the max */
+ /* Don't allow it to go over the maximum */
if (ideal_low_div > max_low_div)
ideal_low_div = max_low_div;
@@ -588,8 +599,8 @@ static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
u64 t_low_ns, t_high_ns;
int ret;
- ret = rk3x_i2c_calc_divs(clk_rate, i2c->scl_frequency, &div_low,
- &div_high);
+ ret = rk3x_i2c_calc_divs(clk_rate, i2c->scl_frequency, i2c->rise_ns,
+ i2c->fall_ns, &div_low, &div_high);
WARN_ONCE(ret != 0, "Could not reach SCL freq %u", i2c->scl_frequency);
@@ -633,9 +644,9 @@ static int rk3x_i2c_clk_notifier_cb(struct notifier_block *nb, unsigned long
switch (event) {
case PRE_RATE_CHANGE:
if (rk3x_i2c_calc_divs(ndata->new_rate, i2c->scl_frequency,
- &div_low, &div_high) != 0) {
+ i2c->rise_ns, i2c->fall_ns, &div_low,
+ &div_high) != 0)
return NOTIFY_STOP;
- }
/* scale up */
if (ndata->new_rate > ndata->old_rate)
@@ -859,6 +870,21 @@ static int rk3x_i2c_probe(struct platform_device *pdev)
i2c->scl_frequency = DEFAULT_SCL_RATE;
}
+ /*
+ * Read rise and fall time from device tree. If not available use
+ * the default maximum timing from the specification.
+ */
+ if (of_property_read_u32(pdev->dev.of_node, "i2c-scl-rising-time-ns",
+ &i2c->rise_ns)) {
+ if (i2c->scl_frequency <= 100000)
+ i2c->rise_ns = 1000;
+ else
+ i2c->rise_ns = 300;
+ }
+ if (of_property_read_u32(pdev->dev.of_node, "i2c-scl-falling-time-ns",
+ &i2c->fall_ns))
+ i2c->fall_ns = 300;
+
strlcpy(i2c->adap.name, "rk3x-i2c", sizeof(i2c->adap.name));
i2c->adap.owner = THIS_MODULE;
i2c->adap.algo = &rk3x_i2c_algorithm;