[PATCH 86/86] [ARM] omap: clk_set_parent: deny changing parent if clock is enabled

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: Russell King <rmk@xxxxxxxxxxxxxxxxxxxxxxx>

Richard Woodruff writes:
| The historic usage of this has been against single use leaf clocks
| (1st instance of gptimer).  When it was used it did:
|       clk_get()
|       clk_set_parent()
|       clk_enable()
|
| This usage was ok for that. Use on a disabled clock is needed.
|
| If there are multiple users on the clock or it is enabled there are
| problems.
|
| The call can still be unfriendly if 2 different drivers are using the
| clock with their own clock get/enable. It might be the function should
| return an error if usecount != 0 to stop surprises.  It is all around
| better if the parenting is done when the clock is off.

This is a good reason to ensure that the clock is not enabled when
clk_set_parent() is called.

Acked-by: Richard Woodruff <r-woodruff2@xxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
---
 arch/arm/mach-omap2/clock.c |    6 ------
 arch/arm/plat-omap/clock.c  |   17 ++++++++++-------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/arch/arm/mach-omap2/clock.c b/arch/arm/mach-omap2/clock.c
index 40cb65b..f49bce9 100644
--- a/arch/arm/mach-omap2/clock.c
+++ b/arch/arm/mach-omap2/clock.c
@@ -807,9 +807,6 @@ int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
 	if (!parent_div)
 		return -EINVAL;
 
-	if (clk->usecount > 0)
-		_omap2_clk_disable(clk);
-
 	/* Set new source value (previous dividers if any in effect) */
 	v = __raw_readl(clk->clksel_reg);
 	v &= ~clk->clksel_mask;
@@ -819,9 +816,6 @@ int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
 
 	_omap2xxx_clk_commit(clk);
 
-	if (clk->usecount > 0)
-		_omap2_clk_enable(clk);
-
 	clk_reparent(clk, new_parent);
 
 	/* CLKSEL clocks follow their parents' rates, divided by a divisor */
diff --git a/arch/arm/plat-omap/clock.c b/arch/arm/plat-omap/clock.c
index 08baa18..2e06145 100644
--- a/arch/arm/plat-omap/clock.c
+++ b/arch/arm/plat-omap/clock.c
@@ -144,13 +144,16 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 		return ret;
 
 	spin_lock_irqsave(&clockfw_lock, flags);
-	if (arch_clock->clk_set_parent)
-		ret = arch_clock->clk_set_parent(clk, parent);
-	if (ret == 0) {
-		if (clk->recalc)
-			clk->rate = clk->recalc(clk);
-		propagate_rate(clk);
-	}
+	if (clk->usecount == 0) {
+		if (arch_clock->clk_set_parent)
+			ret = arch_clock->clk_set_parent(clk, parent);
+		if (ret == 0) {
+			if (clk->recalc)
+				clk->rate = clk->recalc(clk);
+			propagate_rate(clk);
+		}
+	} else
+		ret = -EBUSY;
 	spin_unlock_irqrestore(&clockfw_lock, flags);
 
 	return ret;
-- 
1.6.1.2

--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux Arm (vger)]     [ARM Kernel]     [ARM MSM]     [Linux Tegra]     [Linux WPAN Networking]     [Linux Wireless Networking]     [Maemo Users]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Trails]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux