Modify the internal registration helpers dpll_xa_ref_{dpll,pin}_add()
to reject duplicate registration attempts.

Previously, if a caller attempted to register the same pin multiple
times (with the same ops, priv, and cookie) on the same device, the core
silently increments the reference count and return success. This behavior
is incorrect because if the caller makes these duplicate registrations
then for the first one dpll_pin_registration is allocated and for others
the associated dpll_pin_ref.refcount is incremented. During the first
unregistration the associated dpll_pin_registration is freed and for
others WARN is fired.

Fix this by updating the logic to return `-EEXIST` if a matching
registration is found to enforce a strict "register once" policy.

Fixes: 9431063ad323 ("dpll: core: Add DPLL framework base functions")
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
 drivers/dpll/dpll_core.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index a461095efd8a..8879a7235156 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -83,10 +83,8 @@ dpll_xa_ref_pin_add(struct xarray *xa_pins, struct dpll_pin *pin,
 		if (ref->pin != pin)
 			continue;
 		reg = dpll_pin_registration_find(ref, ops, priv, cookie);
-		if (reg) {
-			refcount_inc(&ref->refcount);
-			return 0;
-		}
+		if (reg)
+			return -EEXIST;
 		ref_exists = true;
 		break;
 	}
@@ -164,10 +162,8 @@ dpll_xa_ref_dpll_add(struct xarray *xa_dplls, struct dpll_device *dpll,
 		if (ref->dpll != dpll)
 			continue;
 		reg = dpll_pin_registration_find(ref, ops, priv, cookie);
-		if (reg) {
-			refcount_inc(&ref->refcount);
-			return 0;
-		}
+		if (reg)
+			return -EEXIST;
 		ref_exists = true;
 		break;
 	}
-- 
2.52.0

On 21/01/2026 13:00, Ivan Vecera wrote:
> Modify the internal registration helpers dpll_xa_ref_{dpll,pin}_add()
> to reject duplicate registration attempts.
> 
> Previously, if a caller attempted to register the same pin multiple
> times (with the same ops, priv, and cookie) on the same device, the core
> silently increments the reference count and return success. This behavior
> is incorrect because if the caller makes these duplicate registrations
> then for the first one dpll_pin_registration is allocated and for others
> the associated dpll_pin_ref.refcount is incremented. During the first
> unregistration the associated dpll_pin_registration is freed and for
> others WARN is fired.
> 
> Fix this by updating the logic to return `-EEXIST` if a matching
> registration is found to enforce a strict "register once" policy.
> 
> Fixes: 9431063ad323 ("dpll: core: Add DPLL framework base functions")
> Signed-off-by: Ivan Vecera <ivecera@redhat.com>
> ---
>   drivers/dpll/dpll_core.c | 12 ++++--------
>   1 file changed, 4 insertions(+), 8 deletions(-)

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>

>From: Ivan Vecera <ivecera@redhat.com>
>Sent: Wednesday, January 21, 2026 2:00 PM
>
>Modify the internal registration helpers dpll_xa_ref_{dpll,pin}_add()
>to reject duplicate registration attempts.
>
>Previously, if a caller attempted to register the same pin multiple
>times (with the same ops, priv, and cookie) on the same device, the core
>silently increments the reference count and return success. This behavior
>is incorrect because if the caller makes these duplicate registrations
>then for the first one dpll_pin_registration is allocated and for others
>the associated dpll_pin_ref.refcount is incremented. During the first
>unregistration the associated dpll_pin_registration is freed and for
>others WARN is fired.
>
>Fix this by updating the logic to return `-EEXIST` if a matching
>registration is found to enforce a strict "register once" policy.
>
>Fixes: 9431063ad323 ("dpll: core: Add DPLL framework base functions")
>Signed-off-by: Ivan Vecera <ivecera@redhat.com>
>---
> drivers/dpll/dpll_core.c | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
>
>diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
>index a461095efd8a..8879a7235156 100644
>--- a/drivers/dpll/dpll_core.c
>+++ b/drivers/dpll/dpll_core.c
>@@ -83,10 +83,8 @@ dpll_xa_ref_pin_add(struct xarray *xa_pins, struct
>dpll_pin *pin,
> 		if (ref->pin != pin)
> 			continue;
> 		reg = dpll_pin_registration_find(ref, ops, priv, cookie);
>-		if (reg) {
>-			refcount_inc(&ref->refcount);
>-			return 0;
>-		}
>+		if (reg)
>+			return -EEXIST;
> 		ref_exists = true;
> 		break;
> 	}
>@@ -164,10 +162,8 @@ dpll_xa_ref_dpll_add(struct xarray *xa_dplls, struct
>dpll_device *dpll,
> 		if (ref->dpll != dpll)
> 			continue;
> 		reg = dpll_pin_registration_find(ref, ops, priv, cookie);
>-		if (reg) {
>-			refcount_inc(&ref->refcount);
>-			return 0;
>-		}
>+		if (reg)
>+			return -EEXIST;
> 		ref_exists = true;
> 		break;
> 	}
>--
>2.52.0

Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>