diff options
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-rk3x.txt | 7 | ||||
| -rw-r--r-- | drivers/i2c/busses/i2c-rk3x.c | 61 |
2 files changed, 48 insertions, 20 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt b/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt index c4fd545720af..f0d71bc52e64 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-rk3x.txt @@ -21,14 +21,17 @@ 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 + - i2c-scl-rising-time-ns : Number of nanoseconds the SCL 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 + - i2c-scl-falling-time-ns : Number of nanoseconds the SCL 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. + - i2c-sda-falling-time-ns : Number of nanoseconds the SDA signal takes to fall + (t(f) in the I2C specification). If not specified we'll use the SCL + value since they are the same in nearly all cases. Example: diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c index 36a922445814..5f96b1b3e3a5 100644 --- a/drivers/i2c/busses/i2c-rk3x.c +++ b/drivers/i2c/busses/i2c-rk3x.c @@ -102,8 +102,9 @@ struct rk3x_i2c { /* Settings */ unsigned int scl_frequency; - unsigned int rise_ns; - unsigned int fall_ns; + unsigned int scl_rise_ns; + unsigned int scl_fall_ns; + unsigned int sda_fall_ns; /* Synchronization & notification */ spinlock_t lock; @@ -437,8 +438,9 @@ 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. + * @scl_rise_ns: How many ns it takes for SCL to rise. + * @scl_fall_ns: How many ns it takes for SCL to fall. + * @sda_fall_ns: How many ns it takes for SDA to fall. * @div_low: Divider output for low * @div_high: Divider output for high * @@ -447,11 +449,13 @@ 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 scl_rise_ns, + unsigned long scl_fall_ns, + unsigned long sda_fall_ns, unsigned long *div_low, unsigned long *div_high) { unsigned long spec_min_low_ns, spec_min_high_ns; - unsigned long spec_max_data_hold_ns; + unsigned long spec_setup_start, spec_max_data_hold_ns; unsigned long data_hold_buffer_ns; unsigned long min_low_ns, min_high_ns; @@ -490,18 +494,35 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate, if (scl_rate <= 100000) { /* Standard-mode */ spec_min_low_ns = 4700; + spec_setup_start = 4700; spec_min_high_ns = 4000; spec_max_data_hold_ns = 3450; data_hold_buffer_ns = 50; } else { /* Fast-mode */ spec_min_low_ns = 1300; + spec_setup_start = 600; spec_min_high_ns = 600; spec_max_data_hold_ns = 900; data_hold_buffer_ns = 50; } - min_low_ns = spec_min_low_ns + fall_ns; - min_high_ns = spec_min_high_ns + rise_ns; + min_high_ns = scl_rise_ns + spec_min_high_ns; + + /* + * Timings for repeated start: + * - controller appears to drop SDA at .875x (7/8) programmed clk high. + * - controller appears to keep SCL high for 2x programmed clk high. + * + * We need to account for those rules in picking our "high" time so + * we meet tSU;STA and tHD;STA times. + */ + min_high_ns = max(min_high_ns, + DIV_ROUND_UP((scl_rise_ns + spec_setup_start) * 1000, 875)); + min_high_ns = max(min_high_ns, + DIV_ROUND_UP((scl_rise_ns + spec_setup_start + + sda_fall_ns + spec_min_high_ns), 2)); + + min_low_ns = scl_fall_ns + spec_min_low_ns; max_low_ns = spec_max_data_hold_ns * 2 - data_hold_buffer_ns; min_total_ns = min_low_ns + min_high_ns; @@ -599,9 +620,9 @@ 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, i2c->rise_ns, - i2c->fall_ns, &div_low, &div_high); - + ret = rk3x_i2c_calc_divs(clk_rate, i2c->scl_frequency, i2c->scl_rise_ns, + i2c->scl_fall_ns, i2c->sda_fall_ns, + &div_low, &div_high); WARN_ONCE(ret != 0, "Could not reach SCL freq %u", i2c->scl_frequency); clk_enable(i2c->clk); @@ -644,8 +665,9 @@ 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, - i2c->rise_ns, i2c->fall_ns, &div_low, - &div_high) != 0) + i2c->scl_rise_ns, i2c->scl_fall_ns, + i2c->sda_fall_ns, + &div_low, &div_high) != 0) return NOTIFY_STOP; /* scale up */ @@ -875,15 +897,18 @@ static int rk3x_i2c_probe(struct platform_device *pdev) * the default maximum timing from the specification. */ if (of_property_read_u32(pdev->dev.of_node, "i2c-scl-rising-time-ns", - &i2c->rise_ns)) { + &i2c->scl_rise_ns)) { if (i2c->scl_frequency <= 100000) - i2c->rise_ns = 1000; + i2c->scl_rise_ns = 1000; else - i2c->rise_ns = 300; + i2c->scl_rise_ns = 300; } if (of_property_read_u32(pdev->dev.of_node, "i2c-scl-falling-time-ns", - &i2c->fall_ns)) - i2c->fall_ns = 300; + &i2c->scl_fall_ns)) + i2c->scl_fall_ns = 300; + if (of_property_read_u32(pdev->dev.of_node, "i2c-sda-falling-time-ns", + &i2c->scl_fall_ns)) + i2c->sda_fall_ns = i2c->scl_fall_ns; strlcpy(i2c->adap.name, "rk3x-i2c", sizeof(i2c->adap.name)); i2c->adap.owner = THIS_MODULE; |