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Commit fb72a059 authored by Soren Brinkmann's avatar Soren Brinkmann Committed by Mike Turquette
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clk: Properly handle notifier return values 



Notifiers may return NOTIFY_(OK|DONE|STOP|BAD). The CCF uses an
inconsistent mix of checking against NOTIFY_STOP or NOTIFY_BAD.
This inconsistency leaves errors undetected in some cases:
clk_set_parent() calls __clk_speculate_rates(), which stops when it
hits a NOTIFIER_BAD (STOP is ignored), and passes this value back to the
caller.
clk_set_parent() compares this return value against NOTIFY_STOP only,
ignoring NOTIFY_BAD returns.

Use NOTIFY_STOP_MASK to detect a negative notifier return value and
document all four return value options.

Signed-off-by: default avatarSoren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: default avatarMike Turquette <mturquette@linaro.org>
parent 312f0f0b

drivers/clk/clk.c

+5 −5
Original line number Diff line number Diff line
@@ -1027,16 +1027,16 @@ static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate) 
	else

		new_rate = parent_rate;



	/* abort the rate change if a driver returns NOTIFY_BAD */

	/* abort rate change if a driver returns NOTIFY_BAD or NOTIFY_STOP */

	if (clk->notifier_count)

		ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);



	if (ret == NOTIFY_BAD)

	if (ret & NOTIFY_STOP_MASK)

		goto out;



	hlist_for_each_entry(child, &clk->children, child_node) {

		ret = __clk_speculate_rates(child, new_rate);

		if (ret == NOTIFY_BAD)

		if (ret & NOTIFY_STOP_MASK)

			break;

	}
@@ -1129,7 +1129,7 @@ static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long even 


	if (clk->notifier_count) {

		ret = __clk_notify(clk, event, clk->rate, clk->new_rate);

		if (ret == NOTIFY_BAD)

		if (ret & NOTIFY_STOP_MASK)

			fail_clk = clk;

	}
@@ -1484,7 +1484,7 @@ int clk_set_parent(struct clk *clk, struct clk *parent) 
		ret = __clk_speculate_rates(clk, p_rate);



	/* abort if a driver objects */

	if (ret == NOTIFY_STOP)

	if (ret & NOTIFY_STOP_MASK)

		goto out;



	/* do the re-parent */

include/linux/clk.h

+4 −4
Original line number Diff line number Diff line
@@ -28,16 +28,16 @@ struct clk; 
 * PRE_RATE_CHANGE - called immediately before the clk rate is changed,

 *     to indicate that the rate change will proceed.  Drivers must

 *     immediately terminate any operations that will be affected by the

 *     rate change.  Callbacks may either return NOTIFY_DONE or

 *     NOTIFY_STOP.

 *     rate change.  Callbacks may either return NOTIFY_DONE, NOTIFY_OK,

 *     NOTIFY_STOP or NOTIFY_BAD.

 *

 * ABORT_RATE_CHANGE: called if the rate change failed for some reason

 *     after PRE_RATE_CHANGE.  In this case, all registered notifiers on

 *     the clk will be called with ABORT_RATE_CHANGE. Callbacks must

 *     always return NOTIFY_DONE.

 *     always return NOTIFY_DONE or NOTIFY_OK.

 *

 * POST_RATE_CHANGE - called after the clk rate change has successfully

 *     completed.  Callbacks must always return NOTIFY_DONE.

 *     completed.  Callbacks must always return NOTIFY_DONE or NOTIFY_OK.

 *

 */

#define PRE_RATE_CHANGE			BIT(0)