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clk: fix CLK_SET_RATE_GATE with clock rate protection 

CLK_SET_RATE_GATE should prevent any operation which may result in a rate
change or glitch while the clock is prepared/enabled.

IOW, the following sequence is not allowed anymore with CLK_SET_RATE_GATE:
* clk_get()
* clk_prepare_enable()
* clk_get_rate()
* clk_set_rate()

At the moment this is enforced on the leaf clock of the operation, not
along the tree. This problematic because, if a PLL has the CLK_RATE_GATE,
it won't be enforced if the clk_set_rate() is called on its child clocks.

Using clock rate protection, we can now enforce CLK_SET_RATE_GATE along the
clock tree

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>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20180619134051.16726-3-jbrunet@baylibre.com
This commit is contained in:
Jerome Brunet 2018-06-19 15:40:51 +02:00 committed by Michael Turquette
parent ce397d215c
commit 9461f7b33d
1 changed files with 13 additions and 3 deletions
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16
drivers/clk/clk.c
View File

@ -691,6 +691,9 @@ static void clk_core_unprepare(struct clk_core *core)
"Unpreparing critical %s\n", core->name))
return;
if (core->flags & CLK_SET_RATE_GATE)
clk_core_rate_unprotect(core);
if (--core->prepare_count > 0)
return;
@ -765,6 +768,16 @@ static int clk_core_prepare(struct clk_core *core)
core->prepare_count++;
/*
* CLK_SET_RATE_GATE is a special case of clock protection
* Instead of a consumer claiming exclusive rate control, it is
* actually the provider which prevents any consumer from making any
* operation which could result in a rate change or rate glitch while
* the clock is prepared.
*/
if (core->flags & CLK_SET_RATE_GATE)
clk_core_rate_protect(core);
return 0;
unprepare:
clk_core_unprepare(core->parent);
@ -1888,9 +1901,6 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
if (clk_core_rate_is_protected(core))
return -EBUSY;
if ((core->flags & CLK_SET_RATE_GATE) && core->prepare_count)
return -EBUSY;
/* calculate new rates and get the topmost changed clock */
top = clk_calc_new_rates(core, req_rate);
if (!top)