Two fixes for the NKMP clks on Allwinner SoCs, a locking fix for clkdev

where we forgot to hold a lock while iterating a list that can change,
 and finally a build fix that adds some stubs for clk APIs that are used
 by devfreq drivers on platforms without the clk APIs.
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Merge tag 'clk-fixes-for-linus' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/clk/linux

Pull clk fixes from Stephen Boyd:
 "Two fixes for the NKMP clks on Allwinner SoCs, a locking fix for
  clkdev where we forgot to hold a lock while iterating a list that can
  change, and finally a build fix that adds some stubs for clk APIs that
  are used by devfreq drivers on platforms without the clk APIs"

* tag 'clk-fixes-for-linus' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/clk/linux:
  clk: Add missing stubs for a few functions
  clkdev: Hold clocks_mutex while iterating clocks list
  clk: sunxi-ng: nkmp: Explain why zero width check is needed
  clk: sunxi-ng: nkmp: Avoid GENMASK(-1, 0)

drivers/clk/clkdev.c

@@ -46,6 +46,8 @@ static struct clk_lookup *clk_find(const char *dev_id, const char *con_id)
 	if (con_id)
 		best_possible += 1;
 
+	lockdep_assert_held(&clocks_mutex);
+
 	list_for_each_entry(p, &clocks, node) {
 		match = 0;
 		if (p->dev_id) {
@@ -402,7 +404,10 @@ void devm_clk_release_clkdev(struct device *dev, const char *con_id,
 	struct clk_lookup *cl;
 	int rval;
 
+	mutex_lock(&clocks_mutex);
 	cl = clk_find(dev_id, con_id);
+	mutex_unlock(&clocks_mutex);
+
 	WARN_ON(!cl);
 	rval = devres_release(dev, devm_clkdev_release,
 			      devm_clk_match_clkdev, cl);

drivers/clk/sunxi-ng/ccu_nkmp.c

@@ -167,7 +167,7 @@ static int ccu_nkmp_set_rate(struct clk_hw *hw, unsigned long rate,
 			   unsigned long parent_rate)
 {
 	struct ccu_nkmp *nkmp = hw_to_ccu_nkmp(hw);
-	u32 n_mask, k_mask, m_mask, p_mask;
+	u32 n_mask = 0, k_mask = 0, m_mask = 0, p_mask = 0;
 	struct _ccu_nkmp _nkmp;
 	unsigned long flags;
 	u32 reg;
@@ -186,10 +186,24 @@ static int ccu_nkmp_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	ccu_nkmp_find_best(parent_rate, rate, &_nkmp);
 
-	n_mask = GENMASK(nkmp->n.width + nkmp->n.shift - 1, nkmp->n.shift);
-	k_mask = GENMASK(nkmp->k.width + nkmp->k.shift - 1, nkmp->k.shift);
-	m_mask = GENMASK(nkmp->m.width + nkmp->m.shift - 1, nkmp->m.shift);
-	p_mask = GENMASK(nkmp->p.width + nkmp->p.shift - 1, nkmp->p.shift);
+	/*
+	 * If width is 0, GENMASK() macro may not generate expected mask (0)
+	 * as it falls under undefined behaviour by C standard due to shifts
+	 * which are equal or greater than width of left operand. This can
+	 * be easily avoided by explicitly checking if width is 0.
+	 */
+	if (nkmp->n.width)
+		n_mask = GENMASK(nkmp->n.width + nkmp->n.shift - 1,
+				 nkmp->n.shift);
+	if (nkmp->k.width)
+		k_mask = GENMASK(nkmp->k.width + nkmp->k.shift - 1,
+				 nkmp->k.shift);
+	if (nkmp->m.width)
+		m_mask = GENMASK(nkmp->m.width + nkmp->m.shift - 1,
+				 nkmp->m.shift);
+	if (nkmp->p.width)
+		p_mask = GENMASK(nkmp->p.width + nkmp->p.shift - 1,
+				 nkmp->p.shift);
 
 	spin_lock_irqsave(nkmp->common.lock, flags);
 

include/linux/clk.h

@@ -811,6 +811,22 @@ static inline bool clk_has_parent(struct clk *clk, struct clk *parent)
 	return true;
 }
 
+static inline int clk_set_rate_range(struct clk *clk, unsigned long min,
+				     unsigned long max)
+{
+	return 0;
+}
+
+static inline int clk_set_min_rate(struct clk *clk, unsigned long rate)
+{
+	return 0;
+}
+
+static inline int clk_set_max_rate(struct clk *clk, unsigned long rate)
+{
+	return 0;
+}
+
 static inline int clk_set_parent(struct clk *clk, struct clk *parent)
 {
 	return 0;