diff options
| -rw-r--r-- | drivers/clk/bcm/clk-bcm2835.c | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c index 8ee0f0b28ea3..58ce6af8452d 100644 --- a/drivers/clk/bcm/clk-bcm2835.c +++ b/drivers/clk/bcm/clk-bcm2835.c @@ -530,6 +530,7 @@ struct bcm2835_clock_data { bool is_vpu_clock; bool is_mash_clock; + bool low_jitter; u32 tcnt_mux; }; @@ -1126,7 +1127,8 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw, int parent_idx, unsigned long rate, u32 *div, - unsigned long *prate) + unsigned long *prate, + unsigned long *avgrate) { struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw); struct bcm2835_cprman *cprman = clock->cprman; @@ -1141,8 +1143,25 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw, *prate = clk_hw_get_rate(parent); *div = bcm2835_clock_choose_div(hw, rate, *prate, true); - return bcm2835_clock_rate_from_divisor(clock, *prate, - *div); + *avgrate = bcm2835_clock_rate_from_divisor(clock, *prate, *div); + + if (data->low_jitter && (*div & CM_DIV_FRAC_MASK)) { + unsigned long high, low; + u32 int_div = *div & ~CM_DIV_FRAC_MASK; + + high = bcm2835_clock_rate_from_divisor(clock, *prate, + int_div); + int_div += CM_DIV_FRAC_MASK + 1; + low = bcm2835_clock_rate_from_divisor(clock, *prate, + int_div); + + /* + * Return a value which is the maximum deviation + * below the ideal rate, for use as a metric. + */ + return *avgrate - max(*avgrate - low, high - *avgrate); + } + return *avgrate; } if (data->frac_bits) @@ -1169,6 +1188,7 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw, *div = curdiv << CM_DIV_FRAC_BITS; *prate = curdiv * best_rate; + *avgrate = best_rate; return best_rate; } @@ -1180,6 +1200,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, bool current_parent_is_pllc; unsigned long rate, best_rate = 0; unsigned long prate, best_prate = 0; + unsigned long avgrate, best_avgrate = 0; size_t i; u32 div; @@ -1204,11 +1225,13 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, continue; rate = bcm2835_clock_choose_div_and_prate(hw, i, req->rate, - &div, &prate); + &div, &prate, + &avgrate); if (rate > best_rate && rate <= req->rate) { best_parent = parent; best_prate = prate; best_rate = rate; + best_avgrate = avgrate; } } @@ -1218,7 +1241,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, req->best_parent_hw = best_parent; req->best_parent_rate = best_prate; - req->rate = best_rate; + req->rate = best_avgrate; return 0; } @@ -2027,6 +2050,7 @@ static const struct bcm2835_clk_desc clk_desc_array[] = { .int_bits = 12, .frac_bits = 12, .is_mash_clock = true, + .low_jitter = true, .tcnt_mux = 23), [BCM2835_CLOCK_PWM] = REGISTER_PER_CLK( .name = "pwm", |