[PATCH v2 1/3] clk: bcm2835: Always round up clock divisor

Remi Pommarel
2015-11-11T14:23:43Z

Make bcm2835_clock_choose_div always 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>
---
drivers/clk/bcm/clk-bcm2835.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index 39bf582..1237716 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1152,18 +1152,19 @@ static u32 bcm2835_clock_choose_div(struct clk_hw *hw,
{
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 ((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);
--
2.0.1