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clk: bcm2835: add a round up ability to the clock divisor

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Make bcm2835_clock_choose_div to optionally round up the chosen MASH divisor
so that the resulting average rate will not be higher than the requested one.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
This commit is contained in:
Remi Pommarel 2015-12-06 17:22:46 +01:00 committed by Michael Turquette
parent 5e63dcc74b
commit 9c95b32ca0
1 changed files with 12 additions and 10 deletions
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22
drivers/clk/bcm/clk-bcm2835.c
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@ -1148,22 +1148,24 @@ static int bcm2835_clock_is_on(struct clk_hw *hw)
static u32 bcm2835_clock_choose_div(struct clk_hw *hw,
unsigned long rate,
unsigned long parent_rate)
unsigned long parent_rate,
bool round_up)
{
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
const struct bcm2835_clock_data *data = clock->data;
u32 unused_frac_mask = GENMASK(CM_DIV_FRAC_BITS - data->frac_bits, 0);
u32 unused_frac_mask =
GENMASK(CM_DIV_FRAC_BITS - data->frac_bits, 0) >> 1;
u64 temp = (u64)parent_rate << CM_DIV_FRAC_BITS;
u64 rem;
u32 div;
do_div(temp, rate);
rem = do_div(temp, rate);
div = temp;
/* Round and mask off the unused bits */
if (unused_frac_mask != 0) {
div += unused_frac_mask >> 1;
div &= ~unused_frac_mask;
}
/* Round up and mask off the unused bits */
if (round_up && ((div & unused_frac_mask) != 0 || rem != 0))
div += unused_frac_mask + 1;
div &= ~unused_frac_mask;
/* Clamp to the limits. */
div = max(div, unused_frac_mask + 1);
@ -1202,7 +1204,7 @@ static long bcm2835_clock_round_rate(struct clk_hw *hw,
unsigned long *parent_rate)
{
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
u32 div = bcm2835_clock_choose_div(hw, rate, *parent_rate);
u32 div = bcm2835_clock_choose_div(hw, rate, *parent_rate, false);
return bcm2835_clock_rate_from_divisor(clock, *parent_rate, div);
}
@ -1271,7 +1273,7 @@ static int bcm2835_clock_set_rate(struct clk_hw *hw,
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
struct bcm2835_cprman *cprman = clock->cprman;
const struct bcm2835_clock_data *data = clock->data;
u32 div = bcm2835_clock_choose_div(hw, rate, parent_rate);
u32 div = bcm2835_clock_choose_div(hw, rate, parent_rate, false);
cprman_write(cprman, data->div_reg, div);