clk: introduce clk_set_phase function & callback

A common operation for a clock signal generator is to shift the phase of
that signal. This patch introduces a new function to the clk.h API to
dynamically adjust the phase of a clock signal. Additionally this patch
introduces support for the new function in the common clock framework
via the .set_phase call back in struct clk_ops.

Signed-off-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>

4 files changed, 116 insertions, 4 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b76fa69b44cb..d87661af0c72 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -117,11 +117,11 @@ static void clk_summary_show_one(struct seq_file *s, struct clk *c, int level)
         if (!c)
                 return;
 
-        seq_printf(s, "%*s%-*s %11d %12d %11lu %10lu\n",
+        seq_printf(s, "%*s%-*s %11d %12d %11lu %10lu %-3d\n",
                    level * 3 + 1, "",
                    30 - level * 3, c->name,
                    c->enable_count, c->prepare_count, clk_get_rate(c),
-                   clk_get_accuracy(c));
+                   clk_get_accuracy(c), clk_get_phase(c));
 }
 
 static void clk_summary_show_subtree(struct seq_file *s, struct clk *c,
@@ -143,8 +143,8 @@ static int clk_summary_show(struct seq_file *s, void *data)
         struct clk *c;
         struct hlist_head **lists = (struct hlist_head **)s->private;
 
-        seq_puts(s, "   clock                         enable_cnt  prepare_cnt        rate   accuracy\n");
-        seq_puts(s, "--------------------------------------------------------------------------------\n");
+        seq_puts(s, "   clock                         enable_cnt  prepare_cnt        rate   accuracy   phase\n");
+        seq_puts(s, "----------------------------------------------------------------------------------------\n");
 
         clk_prepare_lock();
 
@@ -180,6 +180,7 @@ static void clk_dump_one(struct seq_file *s, struct clk *c, int level)
         seq_printf(s, "\"prepare_count\": %d,", c->prepare_count);
         seq_printf(s, "\"rate\": %lu", clk_get_rate(c));
         seq_printf(s, "\"accuracy\": %lu", clk_get_accuracy(c));
+        seq_printf(s, "\"phase\": %d", clk_get_phase(c));
 }
 
 static void clk_dump_subtree(struct seq_file *s, struct clk *c, int level)
@@ -264,6 +265,11 @@ static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry)
         if (!d)
                 goto err_out;
 
+        d = debugfs_create_u32("clk_phase", S_IRUGO, clk->dentry,
+                        (u32 *)&clk->phase);
+        if (!d)
+                goto err_out;
+
         d = debugfs_create_x32("clk_flags", S_IRUGO, clk->dentry,
                         (u32 *)&clk->flags);
         if (!d)
@@ -1739,6 +1745,77 @@ out:
 EXPORT_SYMBOL_GPL(clk_set_parent);
 
 /**
+ * clk_set_phase - adjust the phase shift of a clock signal
+ * @clk: clock signal source
+ * @degrees: number of degrees the signal is shifted
+ *
+ * Shifts the phase of a clock signal by the specified
+ * degrees. Returns 0 on success, -EERROR otherwise.
+ *
+ * This function makes no distinction about the input or reference
+ * signal that we adjust the clock signal phase against. For example
+ * phase locked-loop clock signal generators we may shift phase with
+ * respect to feedback clock signal input, but for other cases the
+ * clock phase may be shifted with respect to some other, unspecified
+ * signal.
+ *
+ * Additionally the concept of phase shift does not propagate through
+ * the clock tree hierarchy, which sets it apart from clock rates and
+ * clock accuracy. A parent clock phase attribute does not have an
+ * impact on the phase attribute of a child clock.
+ */
+int clk_set_phase(struct clk *clk, int degrees)
+{
+        int ret = 0;
+
+        if (!clk)
+                goto out;
+
+        /* sanity check degrees */
+        degrees %= 360;
+        if (degrees < 0)
+                degrees += 360;
+
+        clk_prepare_lock();
+
+        if (!clk->ops->set_phase)
+                goto out_unlock;
+
+        ret = clk->ops->set_phase(clk->hw, degrees);
+
+        if (!ret)
+                clk->phase = degrees;
+
+out_unlock:
+        clk_prepare_unlock();
+
+out:
+        return ret;
+}
+
+/**
+ * clk_get_phase - return the phase shift of a clock signal
+ * @clk: clock signal source
+ *
+ * Returns the phase shift of a clock node in degrees, otherwise returns
+ * -EERROR.
+ */
+int clk_get_phase(struct clk *clk)
+{
+        int ret = 0;
+
+        if (!clk)
+                goto out;
+
+        clk_prepare_lock();
+        ret = clk->phase;
+        clk_prepare_unlock();
+
+out:
+        return ret;
+}
+
+/**
  * __clk_init - initialize the data structures in a struct clk
  * @dev:        device initializing this clk, placeholder for now
  * @clk:        clk being initialized
diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
index efbf70b9fd84..845be30be50f 100644
--- a/include/linux/clk-private.h
+++ b/include/linux/clk-private.h
@@ -46,6 +46,7 @@ struct clk {
         unsigned int            enable_count;
         unsigned int            prepare_count;
         unsigned long           accuracy;
+        int                     phase;
         struct hlist_head       children;
         struct hlist_node       child_node;
         unsigned int            notifier_count;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 411dd7eb2653..201a6195a3eb 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -129,6 +129,10 @@ struct dentry;
  *              set then clock accuracy will be initialized to parent accuracy
  *              or 0 (perfect clock) if clock has no parent.
  *
+ * @set_phase:  Shift the phase this clock signal in degrees specified
+ *              by the second argument. Valid values for degrees are
+ *              0-359. Return 0 on success, otherwise -EERROR.
+ *
  * @init:       Perform platform-specific initialization magic.
  *              This is not not used by any of the basic clock types.
  *              Please consider other ways of solving initialization problems
@@ -177,6 +181,7 @@ struct clk_ops {
                                     unsigned long parent_rate, u8 index);
         unsigned long   (*recalc_accuracy)(struct clk_hw *hw,
                                            unsigned long parent_accuracy);
+        int             (*set_phase)(struct clk_hw *hw, int degrees);
         void            (*init)(struct clk_hw *hw);
         int             (*debug_init)(struct clk_hw *hw, struct dentry *dentry);
 };
diff --git a/include/linux/clk.h b/include/linux/clk.h
index fb5e097d8f72..38bdedd3e389 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -106,6 +106,25 @@ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb);
  */
 long clk_get_accuracy(struct clk *clk);
 
+/**
+ * clk_set_phase - adjust the phase shift of a clock signal
+ * @clk: clock signal source
+ * @degrees: number of degrees the signal is shifted
+ *
+ * Shifts the phase of a clock signal by the specified degrees. Returns 0 on
+ * success, -EERROR otherwise.
+ */
+int clk_set_phase(struct clk *clk, int degrees);
+
+/**
+ * clk_get_phase - return the phase shift of a clock signal
+ * @clk: clock signal source
+ *
+ * Returns the phase shift of a clock node in degrees, otherwise returns
+ * -EERROR.
+ */
+int clk_get_phase(struct clk *clk);
+
 #else
 
 static inline long clk_get_accuracy(struct clk *clk)
@@ -113,6 +132,16 @@ static inline long clk_get_accuracy(struct clk *clk)
         return -ENOTSUPP;
 }
 
+static inline long clk_set_phase(struct clk *clk, int phase)
+{
+        return -ENOTSUPP;
+}
+
+static inline long clk_get_phase(struct clk *clk)
+{
+        return -ENOTSUPP;
+}
+
 #endif
 
 /**