From ca5e089a32c5ffba6c5101fdabdd6dea18041c34 Mon Sep 17 00:00:00 2001 From: Jerome Brunet Date: Fri, 1 Dec 2017 22:51:55 +0100 Subject: [PATCH] clk: use round rate to bail out early in set_rate The current implementation of clk_core_set_rate_nolock() bails out early if the requested rate is exactly the same as the one set. It should bail out if the request would not result in a rate a change. This is important when the rate is not exactly what is requested, which is fairly common with PLLs. Ex: provider able to give any rate with steps of 100Hz - 1st consumer request 48000Hz and gets it. - 2nd consumer request 48010Hz as well. If we were to perform the usual mechanism, we would get 48000Hz as well. The clock would not change so there is no point performing any checks to make sure the clock can change, we know it won't. This is important to prepare the addition of the clock protection mechanism Acked-by: Linus Walleij Tested-by: Quentin Schulz Tested-by: Maxime Ripard Acked-by: Michael Turquette Signed-off-by: Jerome Brunet Signed-off-by: Michael Turquette Link: lkml.kernel.org/r/20171201215200.23523-6-jbrunet@baylibre.com --- drivers/clk/clk.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 322d9ba7e5cd..bbe90babdae4 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1658,16 +1658,37 @@ static void clk_change_rate(struct clk_core *core) clk_change_rate(core->new_child); } +static unsigned long clk_core_req_round_rate_nolock(struct clk_core *core, + unsigned long req_rate) +{ + int ret; + struct clk_rate_request req; + + lockdep_assert_held(&prepare_lock); + + if (!core) + return 0; + + clk_core_get_boundaries(core, &req.min_rate, &req.max_rate); + req.rate = req_rate; + + ret = clk_core_round_rate_nolock(core, &req); + + return ret ? 0 : req.rate; +} + static int clk_core_set_rate_nolock(struct clk_core *core, unsigned long req_rate) { struct clk_core *top, *fail_clk; - unsigned long rate = req_rate; + unsigned long rate; int ret = 0; if (!core) return 0; + rate = clk_core_req_round_rate_nolock(core, req_rate); + /* bail early if nothing to do */ if (rate == clk_core_get_rate_nolock(core)) return 0; @@ -1676,7 +1697,7 @@ static int clk_core_set_rate_nolock(struct clk_core *core, return -EBUSY; /* calculate new rates and get the topmost changed clock */ - top = clk_calc_new_rates(core, rate); + top = clk_calc_new_rates(core, req_rate); if (!top) return -EINVAL;