[RFC 5/9] clk: bcm2835: prefer clocks that use integer dividers
From: kernel at martin.sperl.org <hidden>
Date: 2016-01-19 14:51:36
Also in:
linux-clk, linux-devicetree
Subsystem:
common clk framework, the rest · Maintainers:
Michael Turquette, Stephen Boyd, Linus Torvalds
From: Martin Sperl <redacted> To reduce possible jitter prefer integer dividers over fractional dividers. Signed-off-by: Martin Sperl <redacted> --- drivers/clk/bcm/clk-bcm2835.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
index f1ab525..e5313ba 100644
--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c@@ -1686,6 +1686,24 @@ static int bcm2835_clock_determine_rate_set(struct clk_rate_request *req, return 0; } +static int bcm2835_clock_determine_integer_rate(struct clk_hw *hw, + struct clk_rate_request *req, + struct bcm2835_rates *rates, + size_t rate_cnt) +{ + size_t i; + + /* find first matching */ + for (i = 0; i < rate_cnt; i++) { + if (!divmash_get_divf(rates[i].dmash)) + return bcm2835_clock_determine_rate_set(req, + &rates[i]); + } + + /* nothing found */ + return -EINVAL; +} + static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw, struct clk_rate_request *req, struct bcm2835_rates *rates,
@@ -1729,6 +1747,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, struct bcm2835_rates rates[BIT(CM_SRC_BITS)]; size_t i, rate_cnt = 0; divmash dm; + int err; /* fill in rates */ for (i = 0; i < clk_hw_get_num_parents(hw); ++i) {
@@ -1745,7 +1764,12 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, rate_cnt++; } - /* choose the "closest" one */ + /* find integer rates with preference */ + err = bcm2835_clock_determine_integer_rate(hw, req, rates, rate_cnt); + if (!err) + return 0; + + /* otherwise choose the "closest" one */ return bcm2835_clock_determine_closest_rate(hw, req, rates, rate_cnt); }
--
1.7.10.4