diff options
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/busses/i2c-rk3x.c | 61 |
1 files changed, 43 insertions, 18 deletions
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; |