diff options
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-rk3x.txt | 11 | ||||
| -rw-r--r-- | drivers/i2c/busses/i2c-rk3x.c | 72 |
2 files changed, 60 insertions, 23 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt b/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt index dde6c22ce91..c4fd545720a 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 92462843db6..36a92244581 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 @@ out: * * @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 @@ out: * 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; |