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Commit 9c95b32c authored by Remi Pommarel's avatar Remi Pommarel Committed by Michael Turquette
Browse files

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: default avatarRemi Pommarel <repk@triplefau.lt>
Reviewed-by: default avatarEric Anholt <eric@anholt.net>
Signed-off-by: default avatarMichael Turquette <mturquette@baylibre.com>
parent 5e63dcc7

drivers/clk/bcm/clk-bcm2835.c

+12 −10
Original line number Diff line number Diff line
@@ -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;

	/* 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);