[PATCH v3] clk: scmi: Handle case where child clocks are initialized before their parents

[Sascha Hauer]

The SCMI clock driver currently assumes that parent clocks are always
initialized before their children. However, this assumption can fail if
a child clock is encountered before its parent during probe.

This leads to an issue during initialization of the parent_data array:

    sclk->parent_data[i].hw = hws[sclk->info->parents[i]];

If the parent clock's hardware structure has not been initialized yet,
this assignment results in invalid data.

To resolve this, allocate all struct scmi_clk instances as a contiguous
array at the beginning of the probe and populate the hws[] array
upfront. This ensures that any parent referenced later is already
initialized, regardless of the order in which clocks are processed.

Note that we can no longer free individual scmi_clk instances if
scmi_clk_ops_init() fails which shouldn't be a problem if the SCMI
platform has proper per-agent clock discovery.

Fixes: 65a8a3dd3b95f ("clk: scmi: Add support for clock {set,get}_parent")
Reviewed-by: peng.fan at nxp.com
Reviewed-by: Cristian Marussi <cristian.marussi at arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla at arm.com>
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
Changes in v3:
- Reword commit message
- Add Reviewed-by: Sudeep Holla <sudeep.holla at arm.com>
- Link to v2: https://lore.kernel.org/r/20250612-clk-scmi-children-parent-fix-v2-1-125b26a311f6@pengutronix.de

Changes in v2:
- Collect reviewed-by from Cristian Marussi and Peng Fan
- Do not use a local variable that is only used once (Christian)
- Link to v1: https://lore.kernel.org/r/20250604-clk-scmi-children-parent-fix-v1-1-be206954d866@pengutronix.de
---
 drivers/clk/clk-scmi.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
index 15510c2ff21c0335f5cb30677343bd4ef59c0738..1b1561c84127b9e41bfb6096ceb3626f32c4fee0 100644
--- a/drivers/clk/clk-scmi.c
+++ b/drivers/clk/clk-scmi.c
@@ -404,6 +404,7 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 	const struct scmi_handle *handle = sdev->handle;
 	struct scmi_protocol_handle *ph;
 	const struct clk_ops *scmi_clk_ops_db[SCMI_MAX_CLK_OPS] = {};
+	struct scmi_clk *sclks;
 
 	if (!handle)
 		return -ENODEV;
@@ -430,18 +431,21 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 	transport_is_atomic = handle->is_transport_atomic(handle,
 							  &atomic_threshold_us);
 
+	sclks = devm_kcalloc(dev, count, sizeof(*sclks), GFP_KERNEL);
+	if (!sclks)
+		return -ENOMEM;
+
+	for (idx = 0; idx < count; idx++)
+		hws[idx] = &sclks[idx].hw;
+
 	for (idx = 0; idx < count; idx++) {
-		struct scmi_clk *sclk;
+		struct scmi_clk *sclk = &sclks[idx];
 		const struct clk_ops *scmi_ops;
 
-		sclk = devm_kzalloc(dev, sizeof(*sclk), GFP_KERNEL);
-		if (!sclk)
-			return -ENOMEM;
-
 		sclk->info = scmi_proto_clk_ops->info_get(ph, idx);
 		if (!sclk->info) {
 			dev_dbg(dev, "invalid clock info for idx %d\n", idx);
-			devm_kfree(dev, sclk);
+			hws[idx] = NULL;
 			continue;
 		}
 
@@ -479,13 +483,11 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 		if (err) {
 			dev_err(dev, "failed to register clock %d\n", idx);
 			devm_kfree(dev, sclk->parent_data);
-			devm_kfree(dev, sclk);
 			hws[idx] = NULL;
 		} else {
 			dev_dbg(dev, "Registered clock:%s%s\n",
 				sclk->info->name,
 				scmi_ops->enable ? " (atomic ops)" : "");
-			hws[idx] = &sclk->hw;
 		}
 	}
 

---
base-commit: 5abc7438f1e9d62e91ad775cc83c9594c48d2282
change-id: 20250604-clk-scmi-children-parent-fix-45a8912b8ba0

Best regards,
-- 
Sascha Hauer <s.hauer at pengutronix.de>