[PATCH] ARM: OMAP2+: clockdomain: disabling unused clks

Here's the patch.  The changes to clkdm_clk_disable() are the important 
ones, the rest can be ignored for the purposes of this review.


- Paul

From: Mike Turquette <redacted>
Date: Fri, 9 Nov 2012 11:28:42 -0700
Subject: [PATCH] ARM: OMAP2+: clockdomain: bypass clockdomain handling when
 disabling unused clks

The OMAP port to the common clk framework[1] resulted in spurious WARNs
while disable unused clocks.  This is due to _clkdm_clk_hwmod_disable
catching clkdm->usecount's with a value of zero.  Even less desirable it
would not allow the clkdm_clk_disable function pointer to get called due
to an early return of -ERANGE.

This patch adds a check for such a corner case by skipping the WARN and
early return in the event that clkdm->usecount and clk->enable_usecount
are both zero.  Presumably this could only happen during the check for
unused clocks at boot-time.

[1] http://article.gmane.org/gmane.linux.ports.arm.omap/88824

Signed-off-by: Mike Turquette <redacted>
[paul at pwsan.com: split the hwmod and clock disable cases; modified the
 code to skip the clockdomain handling during the disable-unused-clocks phase]
---
 arch/arm/mach-omap2/clockdomain.c |   91 ++++++++++++++++++++++---------------
 1 file changed, 54 insertions(+), 37 deletions(-)

diff --git a/arch/arm/mach-omap2/clockdomain.c b/arch/arm/mach-omap2/clockdomain.c
index 64e5046..1bd0ff0 100644
--- a/arch/arm/mach-omap2/clockdomain.c
+++ b/arch/arm/mach-omap2/clockdomain.c

@@ -22,6 +22,7 @@
 #include <linux/clk.h>
 #include <linux/limits.h>
 #include <linux/err.h>
+#include <linux/clk-private.h>
 
 #include <linux/io.h>
 

@@ -947,35 +948,6 @@ static int _clkdm_clk_hwmod_enable(struct clockdomain *clkdm)
        return 0;
 }
 
-static int _clkdm_clk_hwmod_disable(struct clockdomain *clkdm)
-{
-       unsigned long flags;
-
-       if (!clkdm || !arch_clkdm || !arch_clkdm->clkdm_clk_disable)
-               return -EINVAL;
-
-       spin_lock_irqsave(&clkdm->lock, flags);
-
-       if (atomic_read(&clkdm->usecount) == 0) {
-               spin_unlock_irqrestore(&clkdm->lock, flags);
-               WARN_ON(1); /* underflow */
-               return -ERANGE;
-       }
-
-       if (atomic_dec_return(&clkdm->usecount) > 0) {
-               spin_unlock_irqrestore(&clkdm->lock, flags);
-               return 0;
-       }
-
-       arch_clkdm->clkdm_clk_disable(clkdm);
-       pwrdm_state_switch(clkdm->pwrdm.ptr);
-       spin_unlock_irqrestore(&clkdm->lock, flags);
-
-       pr_debug("clockdomain: %s: disabled\n", clkdm->name);
-
-       return 0;
-}
-
 /**
  * clkdm_clk_enable - add an enabled downstream clock to this clkdm
  * @clkdm: struct clockdomain *

@@ -1018,15 +990,39 @@ int clkdm_clk_enable(struct clockdomain *clkdm, struct clk *clk)
  */
 int clkdm_clk_disable(struct clockdomain *clkdm, struct clk *clk)
 {
-       /*
-        * XXX Rewrite this code to maintain a list of enabled
-        * downstream clocks for debugging purposes?
-        */
+       unsigned long flags;
+       int force_disable = 0;
 
-       if (!clk)
+       if (!clkdm || !clk || !arch_clkdm || !arch_clkdm->clkdm_clk_disable)
                return -EINVAL;
 
-       return _clkdm_clk_hwmod_disable(clkdm);
+       spin_lock_irqsave(&clkdm->lock, flags);
+
+       /* corner case: disabling unused clocks */
+       force_disable = (__clk_get_enable_count(clk) == 0) ? 1 : 0;
+       if (force_disable)
+               goto ccd_exit;
+
+       if (atomic_read(&clkdm->usecount) == 0) {
+               spin_unlock_irqrestore(&clkdm->lock, flags);
+               WARN_ON(1); /* underflow */
+               return -ERANGE;
+       }
+
+       if (atomic_dec_return(&clkdm->usecount) > 0) {
+               spin_unlock_irqrestore(&clkdm->lock, flags);
+               return 0;
+       }
+
+       arch_clkdm->clkdm_clk_disable(clkdm);
+       pwrdm_state_switch(clkdm->pwrdm.ptr);
+
+       pr_debug("clockdomain: %s: disabled\n", clkdm->name);
+
+ccd_exit:
+       spin_unlock_irqrestore(&clkdm->lock, flags);
+
+       return 0;
 }
 
 /**

@@ -1077,6 +1073,8 @@ int clkdm_hwmod_enable(struct clockdomain *clkdm, struct omap_hwmod *oh)
  */
 int clkdm_hwmod_disable(struct clockdomain *clkdm, struct omap_hwmod *oh)
 {
+       unsigned long flags;
+
        /* The clkdm attribute does not exist yet prior OMAP4 */
        if (cpu_is_omap24xx() || cpu_is_omap34xx())
                return 0;

@@ -1086,9 +1084,28 @@ int clkdm_hwmod_disable(struct clockdomain *clkdm, struct omap_hwmod *oh)
         * downstream hwmods for debugging purposes?
         */
 
-       if (!oh)
+       if (!clkdm || !oh || !arch_clkdm || !arch_clkdm->clkdm_clk_disable)
                return -EINVAL;
 
-       return _clkdm_clk_hwmod_disable(clkdm);
+       spin_lock_irqsave(&clkdm->lock, flags);
+
+       if (atomic_read(&clkdm->usecount) == 0) {
+               spin_unlock_irqrestore(&clkdm->lock, flags);
+               WARN_ON(1); /* underflow */
+               return -ERANGE;
+       }
+
+       if (atomic_dec_return(&clkdm->usecount) > 0) {
+               spin_unlock_irqrestore(&clkdm->lock, flags);
+               return 0;
+       }
+
+       arch_clkdm->clkdm_clk_disable(clkdm);
+       pwrdm_state_switch(clkdm->pwrdm.ptr);
+       spin_unlock_irqrestore(&clkdm->lock, flags);
+
+       pr_debug("clockdomain: %s: disabled\n", clkdm->name);
+
+       return 0;
 }
 

-- 
1.7.10.4