clk: at91: keep slow clk enabled to prevent system hang

All slow clk users are not properly claiming it (get + prepare + enable) before using it. If all users properly claiming this clock release it, the clock is disabled, but faulty users still depends on it, and the system hangs. This fix prevents the slow clock from being disabled, and should solve the hanging issue, but offending drivers should be patched to properly claim this clock. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Reported-by: Bo Shen <voice.shen@atmel.com> Cc: stable@vger.kernel.org Signed-off-by: Michael Turquette <mturquette@linaro.org>

clk: at91: keep slow clk enabled to prevent system hang
All slow clk users are not properly claiming it (get + prepare + enable) before using it. If all users properly claiming this clock release it, the clock is disabled, but faulty users still depends on it, and the system hangs. This fix prevents the slow clock from being disabled, and should solve the hanging issue, but offending drivers should be patched to properly claim this clock. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Reported-by: Bo Shen <voice.shen@atmel.com> Cc: stable@vger.kernel.org Signed-off-by: Michael Turquette <mturquette@linaro.org>
Boris Brezillon · Michael Turquette · Eric Lee · Eric Lee · Eric Lee · Eric Lee
1 parent 98f87a7ba2
Showing 1 changed file with 27 additions and 0 deletions Side-by-side Diff
drivers/clk/at91/clk-slow.c
@@ -70,6 +70,7 @@
  
 #define to_clk_sam9x5_slow(hw) container_of(hw, struct clk_sam9x5_slow, hw)
  
+static struct clk *slow_clk;
  
 static int clk_slow_osc_prepare(struct clk_hw *hw)
 {
@@ -357,6 +358,8 @@
 	clk = clk_register(NULL, &slowck->hw);
 	if (IS_ERR(clk))
 		kfree(slowck);
+	else
+		slow_clk = clk;
  
 	return clk;
 }
@@ -433,6 +436,8 @@
 	clk = clk_register(NULL, &slowck->hw);
 	if (IS_ERR(clk))
 		kfree(slowck);
+	else
+		slow_clk = clk;
  
 	return clk;
 }
@@ -465,4 +470,26 @@
  
 	of_clk_add_provider(np, of_clk_src_simple_get, clk);
 }
+
+/*
+ * FIXME: All slow clk users are not properly claiming it (get + prepare +
+ * enable) before using it.
+ * If all users properly claiming this clock decide that they don't need it
+ * anymore (or are removed), it is disabled while faulty users are still
+ * requiring it, and the system hangs.
+ * Prevent this clock from being disabled until all users are properly
+ * requesting it.
+ * Once this is done we should remove this function and the slow_clk variable.
+ */
+static int __init of_at91_clk_slow_retain(void)
+{
+	if (!slow_clk)
+		return 0;
+
+	__clk_get(slow_clk);
+	clk_prepare_enable(slow_clk);
+
+	return 0;
+}
+arch_initcall(of_at91_clk_slow_retain);
...	...	@@ -70,6 +70,7 @@
70	70
71	71	#define to_clk_sam9x5_slow(hw) container_of(hw, struct clk_sam9x5_slow, hw)
72	72
	73	+static struct clk *slow_clk;
73	74
74	75	static int clk_slow_osc_prepare(struct clk_hw *hw)
75	76	{
...	...	@@ -357,6 +358,8 @@
357	358	clk = clk_register(NULL, &slowck->hw);
358	359	if (IS_ERR(clk))
359	360	kfree(slowck);
	361	+ else
	362	+ slow_clk = clk;
360	363
361	364	return clk;
362	365	}
...	...	@@ -433,6 +436,8 @@
433	436	clk = clk_register(NULL, &slowck->hw);
434	437	if (IS_ERR(clk))
435	438	kfree(slowck);
	439	+ else
	440	+ slow_clk = clk;
436	441
437	442	return clk;
438	443	}
...	...	@@ -465,4 +470,26 @@
465	470
466	471	of_clk_add_provider(np, of_clk_src_simple_get, clk);
467	472	}
	473	+
	474	+/*
	475	+ * FIXME: All slow clk users are not properly claiming it (get + prepare +
	476	+ * enable) before using it.
	477	+ * If all users properly claiming this clock decide that they don't need it
	478	+ * anymore (or are removed), it is disabled while faulty users are still
	479	+ * requiring it, and the system hangs.
	480	+ * Prevent this clock from being disabled until all users are properly
	481	+ * requesting it.
	482	+ * Once this is done we should remove this function and the slow_clk variable.
	483	+ */
	484	+static int __init of_at91_clk_slow_retain(void)
	485	+{
	486	+ if (!slow_clk)
	487	+ return 0;
	488	+
	489	+ __clk_get(slow_clk);
	490	+ clk_prepare_enable(slow_clk);
	491	+
	492	+ return 0;
	493	+}
	494	+arch_initcall(of_at91_clk_slow_retain);