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Commit 9461f7b3 authored by Jerome Brunet's avatar Jerome Brunet Committed by Michael Turquette
Browse files

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: default avatarLinus Walleij <linus.walleij@linaro.org>
Tested-by: default avatarQuentin Schulz <quentin.schulz@free-electrons.com>
Tested-by: default avatarMaxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: default avatarJerome Brunet <jbrunet@baylibre.com>
Signed-off-by: default avatarMichael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20180619134051.16726-3-jbrunet@baylibre.com
parent ce397d21

drivers/clk/clk.c

+13 −3
Original line number Original line Diff line number Diff line
@@ -691,6 +691,9 @@ static void clk_core_unprepare(struct clk_core *core) 
	    "Unpreparing critical %s\n", core->name))

	    "Unpreparing critical %s\n", core->name))

		return;

		return;





	if (core->flags & CLK_SET_RATE_GATE)

		clk_core_rate_unprotect(core);



	if (--core->prepare_count > 0)

	if (--core->prepare_count > 0)

		return;

		return;
@@ -765,6 +768,16 @@ static int clk_core_prepare(struct clk_core *core) 




	core->prepare_count++;

	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;

	return 0;

unprepare:

unprepare:

	clk_core_unprepare(core->parent);

	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))

	if (clk_core_rate_is_protected(core))

		return -EBUSY;

		return -EBUSY;





	if ((core->flags & CLK_SET_RATE_GATE) && core->prepare_count)

		return -EBUSY;



	/* calculate new rates and get the topmost changed clock */

	/* calculate new rates and get the topmost changed clock */

	top = clk_calc_new_rates(core, req_rate);

	top = clk_calc_new_rates(core, req_rate);

	if (!top)

	if (!top)