clk: Allow phase adjustment from debugfs

For testing it may be useful to manually adjust a clock's phase. Add
support for writing to the existing clk_phase debugfs file, with the
written value clamped to [0, 360) to match the behaviour of the
clk_set_phase() function.

This is a dangerous feature, so use the existing define
CLOCK_ALLOW_WRITE_DEBUGFS to allow it only if the source is modified.

Signed-off-by: John Keeping <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/clk.c

···
 
 #define clk_rate_mode	0644
 
+static int clk_phase_set(void *data, u64 val)
+{
+	struct clk_core *core = data;
+	int degrees = do_div(val, 360);
+	int ret;
+
+	clk_prepare_lock();
+	ret = clk_core_set_phase_nolock(core, degrees);
+	clk_prepare_unlock();
+
+	return ret;
+}
+
+#define clk_phase_mode	0644
+
 static int clk_prepare_enable_set(void *data, u64 val)
 {
 	struct clk_core *core = data;
···
 #else
 #define clk_rate_set	NULL
 #define clk_rate_mode	0444
+
+#define clk_phase_set	NULL
+#define clk_phase_mode	0644
 #endif
 
 static int clk_rate_get(void *data, u64 *val)
···
 }
 
 DEFINE_DEBUGFS_ATTRIBUTE(clk_rate_fops, clk_rate_get, clk_rate_set, "%llu\n");
+
+static int clk_phase_get(void *data, u64 *val)
+{
+	struct clk_core *core = data;
+
+	*val = core->phase;
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(clk_phase_fops, clk_phase_get, clk_phase_set, "%llu\n");
 
 static const struct {
 	unsigned long flag;
···
 	debugfs_create_file("clk_min_rate", 0444, root, core, &clk_min_rate_fops);
 	debugfs_create_file("clk_max_rate", 0444, root, core, &clk_max_rate_fops);
 	debugfs_create_ulong("clk_accuracy", 0444, root, &core->accuracy);
-	debugfs_create_u32("clk_phase", 0444, root, &core->phase);
+	debugfs_create_file("clk_phase", clk_phase_mode, root, core,
+			    &clk_phase_fops);
 	debugfs_create_file("clk_flags", 0444, root, core, &clk_flags_fops);
 	debugfs_create_u32("clk_prepare_count", 0444, root, &core->prepare_count);
 	debugfs_create_u32("clk_enable_count", 0444, root, &core->enable_count);