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repkmturquette
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clk: bcm2835: add a round up ability to the clock divisor
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>
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drivers/clk/bcm/clk-bcm2835.c

Lines changed: 12 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1148,22 +1148,24 @@ static int bcm2835_clock_is_on(struct clk_hw *hw)
11481148

11491149
static u32 bcm2835_clock_choose_div(struct clk_hw *hw,
11501150
unsigned long rate,
1151-
unsigned long parent_rate)
1151+
unsigned long parent_rate,
1152+
bool round_up)
11521153
{
11531154
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
11541155
const struct bcm2835_clock_data *data = clock->data;
1155-
u32 unused_frac_mask = GENMASK(CM_DIV_FRAC_BITS - data->frac_bits, 0);
1156+
u32 unused_frac_mask =
1157+
GENMASK(CM_DIV_FRAC_BITS - data->frac_bits, 0) >> 1;
11561158
u64 temp = (u64)parent_rate << CM_DIV_FRAC_BITS;
1159+
u64 rem;
11571160
u32 div;
11581161

1159-
do_div(temp, rate);
1162+
rem = do_div(temp, rate);
11601163
div = temp;
11611164

1162-
/* Round and mask off the unused bits */
1163-
if (unused_frac_mask != 0) {
1164-
div += unused_frac_mask >> 1;
1165-
div &= ~unused_frac_mask;
1166-
}
1165+
/* Round up and mask off the unused bits */
1166+
if (round_up && ((div & unused_frac_mask) != 0 || rem != 0))
1167+
div += unused_frac_mask + 1;
1168+
div &= ~unused_frac_mask;
11671169

11681170
/* Clamp to the limits. */
11691171
div = max(div, unused_frac_mask + 1);
@@ -1202,7 +1204,7 @@ static long bcm2835_clock_round_rate(struct clk_hw *hw,
12021204
unsigned long *parent_rate)
12031205
{
12041206
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
1205-
u32 div = bcm2835_clock_choose_div(hw, rate, *parent_rate);
1207+
u32 div = bcm2835_clock_choose_div(hw, rate, *parent_rate, false);
12061208

12071209
return bcm2835_clock_rate_from_divisor(clock, *parent_rate, div);
12081210
}
@@ -1271,7 +1273,7 @@ static int bcm2835_clock_set_rate(struct clk_hw *hw,
12711273
struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
12721274
struct bcm2835_cprman *cprman = clock->cprman;
12731275
const struct bcm2835_clock_data *data = clock->data;
1274-
u32 div = bcm2835_clock_choose_div(hw, rate, parent_rate);
1276+
u32 div = bcm2835_clock_choose_div(hw, rate, parent_rate, false);
12751277

12761278
cprman_write(cprman, data->div_reg, div);
12771279

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