Re: [PATCH 07/11] firmware: arm_scmi: Harden clock parents discovery

[Cristian Marussi <cristian.marussi@arm.com>]

On Sat, Feb 28, 2026 at 10:39:59AM +0800, Peng Fan wrote:
> On Fri, Feb 27, 2026 at 03:32:21PM +0000, Cristian Marussi wrote:
> >Fix clock parents enumeration to account only for effectively discovered
> >parents during enumeration, avoiding to trust the total number of parents
> >declared upfront by the platform.
> >
> >Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> >---
> > drivers/firmware/arm_scmi/clock.c | 18 ++++++++++--------
> > 1 file changed, 10 insertions(+), 8 deletions(-)
> >
> >diff --git a/drivers/firmware/arm_scmi/clock.c b/drivers/firmware/arm_scmi/clock.c
> >index d0fb5affb5cf..15faa79abed4 100644
> >--- a/drivers/firmware/arm_scmi/clock.c
> >+++ b/drivers/firmware/arm_scmi/clock.c
> >@@ -270,15 +270,15 @@ static int iter_clk_possible_parents_update_state(struct scmi_iterator_state *st
> > 	 * assume it's returned+remaining on first call.
> > 	 */
> > 	if (!st->max_resources) {
> >-		p->clkd->info.num_parents = st->num_returned + st->num_remaining;
> >-		p->clkd->info.parents = devm_kcalloc(p->dev,
> >-						     p->clkd->info.num_parents,
> >+		int num_parents = st->num_returned + st->num_remaining;
> >+
> >+		p->clkd->info.parents = devm_kcalloc(p->dev, num_parents,
> > 						     sizeof(*p->clkd->info.parents),
> > 						     GFP_KERNEL);
> >-		if (!p->clkd->info.parents) {
> >-			p->clkd->info.num_parents = 0;
> >+		if (!p->clkd->info.parents)
> > 			return -ENOMEM;
> >-		}
> >+
> >+		/* max_resources is used by the iterators to control bounds */
> > 		st->max_resources = st->num_returned + st->num_remaining;
> > 	}
> > 
> >@@ -293,9 +293,11 @@ static int iter_clk_possible_parents_process_response(const struct scmi_protocol
> > 	const struct scmi_msg_resp_clock_possible_parents *r = response;
> > 	struct scmi_clk_ipriv *p = priv;
> > 
> >-	u32 *parent = &p->clkd->info.parents[st->desc_index + st->loop_idx];
> >+	p->clkd->info.parents[st->desc_index + st->loop_idx] =
> >+		le32_to_cpu(r->possible_parents[st->loop_idx]);
> > 
> >-	*parent = le32_to_cpu(r->possible_parents[st->loop_idx]);
> >+	/* Count only effectively discovered parents */
> >+	p->clkd->info.num_parents++;
> 
> It maybe good to give a warning, if mismatch between 
> number of effectively discovered parents and "st->num_returned + st->num_remaining"
> 

Indeed there could be sign of something off fw-side...

> Anyway this patch LGTM:
> 
> Reviewed-by: Peng Fan <peng.fan@nxp.com>
>

Thanks,
Cristian