linux-kernel - [PATCH net-next 6/7] net: ipa: kill IPA clock reference count

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Date:   Tue, 10 Aug 2021 14:27:03 -0500
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, evgreen@...omium.org,
        cpratapa@...eaurora.org, subashab@...eaurora.org, elder@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 6/7] net: ipa: kill IPA clock reference count

The runtime power management core code maintains a usage count.  This
count mirrors the IPA clock reference count, and there's no need to
maintain both.  So get rid of the IPA clock reference count and just
rely on the runtime PM usage count to determine when the hardware
should be suspended or resumed.

Use pm_runtime_get_if_active() in ipa_clock_get_additional().  We
care whether power is active, regardless of whether it's in use, so
pass true for its ign_usage_count argument.

The IPA clock mutex is just used to make enabling/disabling the
clock and updating the reference count occur atomically.  Without
the reference count, there's no need for the mutex, so get rid of
that too.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/ipa_clock.c | 77 +++----------------------------------
 1 file changed, 6 insertions(+), 71 deletions(-)

diff --git a/drivers/net/ipa/ipa_clock.c b/drivers/net/ipa/ipa_clock.c
index f1ee0b46da005..ab6626c617b91 100644
--- a/drivers/net/ipa/ipa_clock.c
+++ b/drivers/net/ipa/ipa_clock.c
@@ -4,8 +4,6 @@
  * Copyright (C) 2018-2021 Linaro Ltd.
  */
 
-#include <linux/refcount.h>
-#include <linux/mutex.h>
 #include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/interconnect.h>
@@ -58,8 +56,6 @@ enum ipa_power_flag {
 
 /**
  * struct ipa_clock - IPA clocking information
- * @count:		Clocking reference count
- * @mutex:		Protects clock enable/disable
  * @dev:		IPA device pointer
  * @core:		IPA core clock
  * @flags:		Boolean state flags
@@ -67,8 +63,6 @@ enum ipa_power_flag {
  * @interconnect:	Interconnect array
  */
 struct ipa_clock {
-	refcount_t count;
-	struct mutex mutex; /* protects clock enable/disable */
 	struct device *dev;
 	struct clk *core;
 	DECLARE_BITMAP(flags, IPA_POWER_FLAG_COUNT);
@@ -276,78 +270,24 @@ static int ipa_runtime_idle(struct device *dev)
  */
 bool ipa_clock_get_additional(struct ipa *ipa)
 {
-	struct device *dev;
-	int ret;
-
-	if (!refcount_inc_not_zero(&ipa->clock->count))
-		return false;
-
-	dev = &ipa->pdev->dev;
-	ret = pm_runtime_get_sync(dev);
-	if (ret < 0)
-		dev_err(dev, "error %d enabling power\n", ret);
-
-	return true;
+	return pm_runtime_get_if_active(&ipa->pdev->dev, true) > 0;
 }
 
 /* Get an IPA clock reference.  If the reference count is non-zero, it is
- * incremented and return is immediate.  Otherwise it is checked again
- * under protection of the mutex, and if appropriate the IPA clock
- * is enabled.
- *
- * Incrementing the reference count is intentionally deferred until
- * after the clock is running and endpoints are resumed.
+ * incremented and return is immediate.  Otherwise the IPA clock is
+ * enabled.
  */
 int ipa_clock_get(struct ipa *ipa)
 {
-	struct ipa_clock *clock = ipa->clock;
-	struct device *dev;
-	int ret;
-
-	/* If the clock is running, just bump the reference count */
-	if (ipa_clock_get_additional(ipa))
-		return 1;
-
-	/* Otherwise get the mutex and check again */
-	mutex_lock(&clock->mutex);
-
-	/* A reference might have been added before we got the mutex. */
-	if (ipa_clock_get_additional(ipa)) {
-		ret = 1;
-		goto out_mutex_unlock;
-	}
-
-	dev = &ipa->pdev->dev;
-	ret = pm_runtime_get_sync(dev);
-
-	refcount_set(&clock->count, 1);
-
-out_mutex_unlock:
-	mutex_unlock(&clock->mutex);
-
-	return ret;
+	return pm_runtime_get_sync(&ipa->pdev->dev);
 }
 
 /* Attempt to remove an IPA clock reference.  If this represents the
- * last reference, disable the IPA clock under protection of the mutex.
+ * last reference, disable the IPA clock.
  */
 int ipa_clock_put(struct ipa *ipa)
 {
-	struct device *dev = &ipa->pdev->dev;
-	struct ipa_clock *clock = ipa->clock;
-	int last;
-	int ret;
-
-	/* If this is not the last reference there's nothing more to do */
-	last = refcount_dec_and_mutex_lock(&clock->count, &clock->mutex);
-
-	ret = pm_runtime_put(dev);
-	if (!last)
-		return ret;
-
-	mutex_unlock(&clock->mutex);
-
-	return ret;
+	return pm_runtime_put(&ipa->pdev->dev);
 }
 
 /* Return the current IPA core clock rate */
@@ -425,9 +365,6 @@ ipa_clock_init(struct device *dev, const struct ipa_clock_data *data)
 	if (ret)
 		goto err_kfree;
 
-	mutex_init(&clock->mutex);
-	refcount_set(&clock->count, 0);
-
 	pm_runtime_dont_use_autosuspend(dev);
 	pm_runtime_enable(dev);
 
@@ -446,9 +383,7 @@ void ipa_clock_exit(struct ipa_clock *clock)
 {
 	struct clk *clk = clock->core;
 
-	WARN_ON(refcount_read(&clock->count) != 0);
 	pm_runtime_disable(clock->dev);
-	mutex_destroy(&clock->mutex);
 	ipa_interconnect_exit(clock);
 	kfree(clock);
 	clk_put(clk);
-- 
2.27.0