[PATCH v2 65/65] clk: Warn if we register a mux without determine_rate

[Maxime Ripard]

The determine_rate hook allows to select the proper parent and its rate
for a given clock configuration. On another hand, set_parent is there to
change the parent of a mux.

Some clocks provide a set_parent hook but don't implement
determine_rate. In such a case, set_parent is pretty much useless since
the clock framework will always assume the current parent is to be used,
and we will thus never change it.

This situation can be solved in two ways:
  - either we don't need to change the parent, and we thus shouldn't
    implement set_parent;
  - or we don't want to change the parent, in this case we should set
    CLK_SET_RATE_NO_REPARENT;
  - or we're missing a determine_rate implementation.

The latter is probably just an oversight from the driver's author, and
we should thus raise their awareness about the fact that the current
state of the driver is confusing.

It's not clear at this point how many drivers are affected though, so
let's make it a warning instead of an error for now.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
Signed-off-by: Maxime Ripard <maxime at cerno.tech>
---
 drivers/clk/clk.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 495d7497cc43..9eb0343629cc 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3701,6 +3701,13 @@ static int __clk_core_init(struct clk_core *core)
 		goto out;
 	}
 
+	if (core->ops->set_parent && !core->ops->determine_rate) {
+		pr_err("%s: %s must implement .set_parent & .determine_rate\n",
+			__func__, core->name);
+		ret = -EINVAL;
+		goto out;
+	}
+
 	if (core->num_parents > 1 && !core->ops->get_parent) {
 		pr_err("%s: %s must implement .get_parent as it has multi parents\n",
 		       __func__, core->name);

-- 
b4 0.11.0-dev-99e3a