OPP updates for 6.18

- Add support to find OPP for a set of keys (Krishna Chaitanya Chundru).
 
 - Minor optimization to OPP Rust implementation (Onur Özkan).
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Merge tag 'opp-updates-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm

Merge OPP (operating performance points) updates for 6.18 from Viresh
Kumar:

"- Add support to find OPP for a set of keys (Krishna Chaitanya Chundru).

 - Minor optimization to OPP Rust implementation (Onur Özkan)."

* tag 'opp-updates-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm:
  OPP: Add support to find OPP for a set of keys
  rust: opp: use to_result for error handling

drivers/opp/core.c

@@ -476,6 +476,16 @@ static unsigned long _read_bw(struct dev_pm_opp *opp, int index)
 	return opp->bandwidth[index].peak;
 }
 
+static unsigned long _read_opp_key(struct dev_pm_opp *opp, int index,
+				   struct dev_pm_opp_key *key)
+{
+	key->bw = opp->bandwidth ? opp->bandwidth[index].peak : 0;
+	key->freq = opp->rates[index];
+	key->level = opp->level;
+
+	return true;
+}
+
 /* Generic comparison helpers */
 static bool _compare_exact(struct dev_pm_opp **opp, struct dev_pm_opp *temp_opp,
 			   unsigned long opp_key, unsigned long key)
@@ -509,6 +519,22 @@ static bool _compare_floor(struct dev_pm_opp **opp, struct dev_pm_opp *temp_opp,
 	return false;
 }
 
+static bool _compare_opp_key_exact(struct dev_pm_opp **opp,
+		struct dev_pm_opp *temp_opp, struct dev_pm_opp_key *opp_key,
+		struct dev_pm_opp_key *key)
+{
+	bool level_match = (key->level == OPP_LEVEL_UNSET || opp_key->level == key->level);
+	bool freq_match = (key->freq == 0 || opp_key->freq == key->freq);
+	bool bw_match = (key->bw == 0 || opp_key->bw == key->bw);
+
+	if (freq_match && level_match && bw_match) {
+		*opp = temp_opp;
+		return true;
+	}
+
+	return false;
+}
+
 /* Generic key finding helpers */
 static struct dev_pm_opp *_opp_table_find_key(struct opp_table *opp_table,
 		unsigned long *key, int index, bool available,
@@ -541,6 +567,37 @@ static struct dev_pm_opp *_opp_table_find_key(struct opp_table *opp_table,
 	return opp;
 }
 
+static struct dev_pm_opp *_opp_table_find_opp_key(struct opp_table *opp_table,
+		struct dev_pm_opp_key *key, bool available,
+		unsigned long (*read)(struct dev_pm_opp *opp, int index,
+				      struct dev_pm_opp_key *key),
+		bool (*compare)(struct dev_pm_opp **opp, struct dev_pm_opp *temp_opp,
+				struct dev_pm_opp_key *opp_key, struct dev_pm_opp_key *key),
+		bool (*assert)(struct opp_table *opp_table, unsigned int index))
+{
+	struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
+	struct dev_pm_opp_key temp_key;
+
+	/* Assert that the requirement is met */
+	if (!assert(opp_table, 0))
+		return ERR_PTR(-EINVAL);
+
+	guard(mutex)(&opp_table->lock);
+
+	list_for_each_entry(temp_opp, &opp_table->opp_list, node) {
+		if (temp_opp->available == available) {
+			read(temp_opp, 0, &temp_key);
+			if (compare(&opp, temp_opp, &temp_key, key)) {
+				/* Increment the reference count of OPP */
+				dev_pm_opp_get(opp);
+				break;
+			}
+		}
+	}
+
+	return opp;
+}
+
 static struct dev_pm_opp *
 _find_key(struct device *dev, unsigned long *key, int index, bool available,
 	  unsigned long (*read)(struct dev_pm_opp *opp, int index),
@@ -632,6 +689,48 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_find_freq_exact);
 
+/**
+ * dev_pm_opp_find_key_exact() - Search for an OPP with exact key set
+ * @dev:		Device for which the OPP is being searched
+ * @key:		OPP key set to match
+ * @available:		true/false - match for available OPP
+ *
+ * Search for an exact match of the key set in the OPP table.
+ *
+ * Return: A matching opp on success, else ERR_PTR in case of error.
+ * Possible error values:
+ * EINVAL:	for bad pointers
+ * ERANGE:	no match found for search
+ * ENODEV:	if device not found in list of registered devices
+ *
+ * Note: 'available' is a modifier for the search. If 'available' == true,
+ * then the match is for exact matching key and is available in the stored
+ * OPP table. If false, the match is for exact key which is not available.
+ *
+ * This provides a mechanism to enable an OPP which is not available currently
+ * or the opposite as well.
+ *
+ * The callers are required to call dev_pm_opp_put() for the returned OPP after
+ * use.
+ */
+struct dev_pm_opp *dev_pm_opp_find_key_exact(struct device *dev,
+					     struct dev_pm_opp_key *key,
+					     bool available)
+{
+	struct opp_table *opp_table __free(put_opp_table) = _find_opp_table(dev);
+
+	if (IS_ERR(opp_table)) {
+		dev_err(dev, "%s: OPP table not found (%ld)\n", __func__,
+			PTR_ERR(opp_table));
+		return ERR_CAST(opp_table);
+	}
+
+	return _opp_table_find_opp_key(opp_table, key, available,
+				       _read_opp_key, _compare_opp_key_exact,
+				       assert_single_clk);
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_find_key_exact);
+
 /**
  * dev_pm_opp_find_freq_exact_indexed() - Search for an exact freq for the
  *					 clock corresponding to the index

include/linux/pm_opp.h

@@ -98,6 +98,25 @@ struct dev_pm_opp_data {
 	unsigned long u_volt;
 };
 
+/**
+ * struct dev_pm_opp_key - Key used to identify OPP entries
+ * @freq:       Frequency in Hz. Use 0 if frequency is not to be matched.
+ * @level:      Performance level associated with the OPP entry.
+ *              Use OPP_LEVEL_UNSET if level is not to be matched.
+ * @bw:         Bandwidth associated with the OPP entry.
+ *              Use 0 if bandwidth is not to be matched.
+ *
+ * This structure is used to uniquely identify an OPP entry based on
+ * frequency, performance level, and bandwidth. Each field can be
+ * selectively ignored during matching by setting it to its respective
+ * NOP value.
+ */
+struct dev_pm_opp_key {
+	unsigned long freq;
+	unsigned int level;
+	u32 bw;
+};
+
 #if defined(CONFIG_PM_OPP)
 
 struct opp_table *dev_pm_opp_get_opp_table(struct device *dev);
@@ -131,6 +150,10 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
 					      unsigned long freq,
 					      bool available);
 
+struct dev_pm_opp *dev_pm_opp_find_key_exact(struct device *dev,
+					     struct dev_pm_opp_key *key,
+					     bool available);
+
 struct dev_pm_opp *
 dev_pm_opp_find_freq_exact_indexed(struct device *dev, unsigned long freq,
 				   u32 index, bool available);
@@ -289,6 +312,13 @@ static inline struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+static inline struct dev_pm_opp *dev_pm_opp_find_key_exact(struct device *dev,
+							   struct dev_pm_opp_key *key,
+							   bool available)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
 static inline struct dev_pm_opp *
 dev_pm_opp_find_freq_exact_indexed(struct device *dev, unsigned long freq,
 				   u32 index, bool available)

rust/kernel/opp.rs

@@ -12,7 +12,7 @@ use crate::{
     clk::Hertz,
     cpumask::{Cpumask, CpumaskVar},
     device::Device,
-    error::{code::*, from_err_ptr, from_result, to_result, Error, Result, VTABLE_DEFAULT_ERROR},
+    error::{code::*, from_err_ptr, from_result, to_result, Result, VTABLE_DEFAULT_ERROR},
     ffi::c_ulong,
     prelude::*,
     str::CString,
@@ -500,11 +500,8 @@ impl<T: ConfigOps + Default> Config<T> {
         // requirements. The OPP core guarantees not to access fields of [`Config`] after this call
         // and so we don't need to save a copy of them for future use.
         let ret = unsafe { bindings::dev_pm_opp_set_config(dev.as_raw(), &mut config) };
-        if ret < 0 {
-            Err(Error::from_errno(ret))
-        } else {
-            Ok(ConfigToken(ret))
-        }
+
+        to_result(ret).map(|()| ConfigToken(ret))
     }
 
     /// Config's clk callback.
@@ -713,11 +710,8 @@ impl Table {
         // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
         // requirements.
         let ret = unsafe { bindings::dev_pm_opp_get_opp_count(self.dev.as_raw()) };
-        if ret < 0 {
-            Err(Error::from_errno(ret))
-        } else {
-            Ok(ret as u32)
-        }
+
+        to_result(ret).map(|()| ret as u32)
     }
 
     /// Returns max clock latency (in nanoseconds) of the [`OPP`]s in the [`Table`].