This is a note to let you know that I've just added the patch titled

clk: use round rate to bail out early in set_rate

to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: clk-use-round-rate-to-bail-out-early-in-set_rate.patch and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Mar 22 14:03:40 CET 2018

From: Jerome Brunet jbrunet@baylibre.com Date: Fri, 1 Dec 2017 22:51:55 +0100 Subject: clk: use round rate to bail out early in set_rate

From: Jerome Brunet jbrunet@baylibre.com

[ Upstream commit ca5e089a32c5ffba6c5101fdabdd6dea18041c34 ]

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 linus.walleij@linaro.org Tested-by: Quentin Schulz quentin.schulz@free-electrons.com Tested-by: Maxime Ripard maxime.ripard@free-electrons.com Acked-by: Michael Turquette mturquette@baylibre.com Signed-off-by: Jerome Brunet jbrunet@baylibre.com Signed-off-by: Michael Turquette mturquette@baylibre.com Link: lkml.kernel.org/r/20171201215200.23523-6-jbrunet@baylibre.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/clk/clk.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-)

--- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1642,16 +1642,37 @@ static void clk_change_rate(struct clk_c clk_pm_runtime_put(core); }

+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; @@ -1660,7 +1681,7 @@ static int clk_core_set_rate_nolock(stru 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;

Patches currently in stable-queue which might be from jbrunet@baylibre.com are

queue-4.15/clk-check-ops-pointer-on-clock-register.patch queue-4.15/net-phy-meson-gxl-check-phy_write-return-value.patch queue-4.15/clk-use-round-rate-to-bail-out-early-in-set_rate.patch