dpll: Support dynamic pin index allocation

Allow drivers to register DPLL pins without manually specifying a pin
index.

Currently, drivers must provide a unique pin index when calling
dpll_pin_get(). This works well for hardware-mapped pins but creates
friction for drivers handling virtual pins or those without a strict
hardware indexing scheme.

Introduce DPLL_PIN_IDX_UNSPEC (U32_MAX). When a driver passes this
value as the pin index:
1. The core allocates a unique index using an IDA
2. The allocated index is mapped to a range starting above `INT_MAX`

This separation ensures that dynamically allocated indices never collide
with standard driver-provided hardware indices, which are assumed to be
within the `0` to `INT_MAX` range. The index is automatically freed when
the pin is released in dpll_pin_put().

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Link: https://patch.msgid.link/20260203174002.705176-5-ivecera@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index b05fe2ba46d910af87e171b697dba8da2a6c4113..59081cf2c73ae08c099e53aca0ee2878a2f61d65 100644 (file)
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -10,6 +10,7 @@
 
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/idr.h>
 #include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/string.h>
@@ -24,6 +25,7 @@ DEFINE_XARRAY_FLAGS(dpll_device_xa, XA_FLAGS_ALLOC);
 DEFINE_XARRAY_FLAGS(dpll_pin_xa, XA_FLAGS_ALLOC);
 
 static RAW_NOTIFIER_HEAD(dpll_notifier_chain);
+static DEFINE_IDA(dpll_pin_idx_ida);
 
 static u32 dpll_device_xa_id;
 static u32 dpll_pin_xa_id;
@@ -464,6 +466,36 @@ void dpll_device_unregister(struct dpll_device *dpll,
 }
 EXPORT_SYMBOL_GPL(dpll_device_unregister);
 
+static int dpll_pin_idx_alloc(u32 *pin_idx)
+{
+       int ret;
+
+       if (!pin_idx)
+               return -EINVAL;
+
+       /* Alloc unique number from IDA. Number belongs to <0, INT_MAX> range */
+       ret = ida_alloc(&dpll_pin_idx_ida, GFP_KERNEL);
+       if (ret < 0)
+               return ret;
+
+       /* Map the value to dynamic pin index range <INT_MAX+1, U32_MAX> */
+       *pin_idx = (u32)ret + INT_MAX + 1;
+
+       return 0;
+}
+
+static void dpll_pin_idx_free(u32 pin_idx)
+{
+       if (pin_idx <= INT_MAX)
+               return; /* Not a dynamic pin index */
+
+       /* Map the index value from dynamic pin index range to IDA range and
+        * free it.
+        */
+       pin_idx -= (u32)INT_MAX + 1;
+       ida_free(&dpll_pin_idx_ida, pin_idx);
+}
+
 static void dpll_pin_prop_free(struct dpll_pin_properties *prop)
 {
        kfree(prop->package_label);
@@ -521,9 +553,18 @@ dpll_pin_alloc(u64 clock_id, u32 pin_idx, struct module *module,
        struct dpll_pin *pin;
        int ret;
 
+       if (pin_idx == DPLL_PIN_IDX_UNSPEC) {
+               ret = dpll_pin_idx_alloc(&pin_idx);
+               if (ret)
+                       return ERR_PTR(ret);
+       } else if (pin_idx > INT_MAX) {
+               return ERR_PTR(-EINVAL);
+       }
        pin = kzalloc(sizeof(*pin), GFP_KERNEL);
-       if (!pin)
-               return ERR_PTR(-ENOMEM);
+       if (!pin) {
+               ret = -ENOMEM;
+               goto err_pin_alloc;
+       }
        pin->pin_idx = pin_idx;
        pin->clock_id = clock_id;
        pin->module = module;
@@ -551,6 +592,8 @@ err_xa_alloc:
        dpll_pin_prop_free(&pin->prop);
 err_pin_prop:
        kfree(pin);
+err_pin_alloc:
+       dpll_pin_idx_free(pin_idx);
        return ERR_PTR(ret);
 }
 
@@ -654,6 +697,7 @@ void dpll_pin_put(struct dpll_pin *pin)
                xa_destroy(&pin->ref_sync_pins);
                dpll_pin_prop_free(&pin->prop);
                fwnode_handle_put(pin->fwnode);
+               dpll_pin_idx_free(pin->pin_idx);
                kfree_rcu(pin, rcu);
        }
        mutex_unlock(&dpll_lock);

diff --git a/include/linux/dpll.h b/include/linux/dpll.h
index 8ed90dfc65f058c9d6c41b5410478ddb7ca4b052..8fff048131f1d6320146439023796fb147649f0a 100644 (file)
--- a/include/linux/dpll.h
+++ b/include/linux/dpll.h
@@ -240,6 +240,8 @@ int dpll_device_register(struct dpll_device *dpll, enum dpll_type type,
 void dpll_device_unregister(struct dpll_device *dpll,
                            const struct dpll_device_ops *ops, void *priv);
 
+#define DPLL_PIN_IDX_UNSPEC    U32_MAX
+
 struct dpll_pin *
 dpll_pin_get(u64 clock_id, u32 dev_driver_id, struct module *module,
             const struct dpll_pin_properties *prop);