NTB: Alter Scratchpads API to support multi-ports devices

Even though there is no any real NTB hardware, which would have both more
than two ports and Scratchpad registers, it is logically correct to have
Scratchpad API accepting a peer port index as well. Intel/AMD drivers utilize
Primary and Secondary topology to split Scratchpad between connected root
devices. Since port-index API introduced, Intel/AMD NTB hardware drivers can
use device port to determine which Scratchpad registers actually belong to
local and peer devices. The same approach can be used if some potential
hardware in future will be multi-port and have some set of Scratchpads.
Here are the brief of changes in the API:
 ntb_spad_count() - return number of Scratchpads per each port
 ntb_peer_spad_addr(pidx, sidx) - address of Scratchpad register of the
peer device with pidx-index
 ntb_peer_spad_read(pidx, sidx) - read specified Scratchpad register of the
peer with pidx-index
 ntb_peer_spad_write(pidx, sidx) - write data to Scratchpad register of the
peer with pidx-index

Since there is hardware which doesn't support Scratchpad registers, the
corresponding API methods are now made optional.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

1 files changed, 45 insertions, 28 deletions

diff --git a/include/linux/ntb.h b/include/linux/ntb.h
index 2ea83f91a236..4e3cd56af732 100644
--- a/include/linux/ntb.h
+++ b/include/linux/ntb.h
@@ -288,13 +288,14 @@ struct ntb_dev_ops {
 	int (*spad_is_unsafe)(struct ntb_dev *ntb);
 	int (*spad_count)(struct ntb_dev *ntb);
 
-	u32 (*spad_read)(struct ntb_dev *ntb, int idx);
-	int (*spad_write)(struct ntb_dev *ntb, int idx, u32 val);
+	u32 (*spad_read)(struct ntb_dev *ntb, int sidx);
+	int (*spad_write)(struct ntb_dev *ntb, int sidx, u32 val);
 
-	int (*peer_spad_addr)(struct ntb_dev *ntb, int idx,
+	int (*peer_spad_addr)(struct ntb_dev *ntb, int pidx, int sidx,
 			      phys_addr_t *spad_addr);
-	u32 (*peer_spad_read)(struct ntb_dev *ntb, int idx);
-	int (*peer_spad_write)(struct ntb_dev *ntb, int idx, u32 val);
+	u32 (*peer_spad_read)(struct ntb_dev *ntb, int pidx, int sidx);
+	int (*peer_spad_write)(struct ntb_dev *ntb, int pidx, int sidx,
+			       u32 val);
 };
 
 static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
@@ -335,13 +336,12 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
 		/* ops->peer_db_read_mask		&& */
 		/* ops->peer_db_set_mask		&& */
 		/* ops->peer_db_clear_mask		&& */
-		/* ops->spad_is_unsafe			&& */
-		ops->spad_count				&&
-		ops->spad_read				&&
-		ops->spad_write				&&
-		/* ops->peer_spad_addr			&& */
-		/* ops->peer_spad_read			&& */
-		ops->peer_spad_write			&&
+		/* !ops->spad_is_unsafe == !ops->spad_count	&& */
+		!ops->spad_read == !ops->spad_count		&&
+		!ops->spad_write == !ops->spad_count		&&
+		/* !ops->peer_spad_addr == !ops->spad_count	&& */
+		/* !ops->peer_spad_read == !ops->spad_count	&& */
+		!ops->peer_spad_write == !ops->spad_count	&&
 		1;
 }
 
@@ -1176,47 +1176,58 @@ static inline int ntb_spad_is_unsafe(struct ntb_dev *ntb)
  * @ntb:	NTB device context.
  *
  * Hardware and topology may support a different number of scratchpads.
+ * Although it must be the same for all ports per NTB device.
  *
  * Return: the number of scratchpads.
  */
 static inline int ntb_spad_count(struct ntb_dev *ntb)
 {
+	if (!ntb->ops->spad_count)
+		return 0;
+
 	return ntb->ops->spad_count(ntb);
 }
 
 /**
  * ntb_spad_read() - read the local scratchpad register
  * @ntb:	NTB device context.
- * @idx:	Scratchpad index.
+ * @sidx:	Scratchpad index.
  *
  * Read the local scratchpad register, and return the value.
  *
  * Return: The value of the local scratchpad register.
  */
-static inline u32 ntb_spad_read(struct ntb_dev *ntb, int idx)
+static inline u32 ntb_spad_read(struct ntb_dev *ntb, int sidx)
 {
-	return ntb->ops->spad_read(ntb, idx);
+	if (!ntb->ops->spad_read)
+		return ~(u32)0;
+
+	return ntb->ops->spad_read(ntb, sidx);
 }
 
 /**
  * ntb_spad_write() - write the local scratchpad register
  * @ntb:	NTB device context.
- * @idx:	Scratchpad index.
+ * @sidx:	Scratchpad index.
  * @val:	Scratchpad value.
  *
  * Write the value to the local scratchpad register.
  *
  * Return: Zero on success, otherwise an error number.
  */
-static inline int ntb_spad_write(struct ntb_dev *ntb, int idx, u32 val)
+static inline int ntb_spad_write(struct ntb_dev *ntb, int sidx, u32 val)
 {
-	return ntb->ops->spad_write(ntb, idx, val);
+	if (!ntb->ops->spad_write)
+		return -EINVAL;
+
+	return ntb->ops->spad_write(ntb, sidx, val);
 }
 
 /**
  * ntb_peer_spad_addr() - address of the peer scratchpad register
  * @ntb:	NTB device context.
- * @idx:	Scratchpad index.
+ * @pidx:	Port index of peer device.
+ * @sidx:	Scratchpad index.
  * @spad_addr:	OUT - The address of the peer scratchpad register.
  *
  * Return the address of the peer doorbell register.  This may be used, for
@@ -1224,45 +1235,51 @@ static inline int ntb_spad_write(struct ntb_dev *ntb, int idx, u32 val)
  *
  * Return: Zero on success, otherwise an error number.
  */
-static inline int ntb_peer_spad_addr(struct ntb_dev *ntb, int idx,
+static inline int ntb_peer_spad_addr(struct ntb_dev *ntb, int pidx, int sidx,
 				     phys_addr_t *spad_addr)
 {
 	if (!ntb->ops->peer_spad_addr)
 		return -EINVAL;
 
-	return ntb->ops->peer_spad_addr(ntb, idx, spad_addr);
+	return ntb->ops->peer_spad_addr(ntb, pidx, sidx, spad_addr);
 }
 
 /**
  * ntb_peer_spad_read() - read the peer scratchpad register
  * @ntb:	NTB device context.
- * @idx:	Scratchpad index.
+ * @pidx:	Port index of peer device.
+ * @sidx:	Scratchpad index.
  *
  * Read the peer scratchpad register, and return the value.
  *
  * Return: The value of the local scratchpad register.
  */
-static inline u32 ntb_peer_spad_read(struct ntb_dev *ntb, int idx)
+static inline u32 ntb_peer_spad_read(struct ntb_dev *ntb, int pidx, int sidx)
 {
 	if (!ntb->ops->peer_spad_read)
-		return 0;
+		return ~(u32)0;
 
-	return ntb->ops->peer_spad_read(ntb, idx);
+	return ntb->ops->peer_spad_read(ntb, pidx, sidx);
 }
 
 /**
  * ntb_peer_spad_write() - write the peer scratchpad register
  * @ntb:	NTB device context.
- * @idx:	Scratchpad index.
+ * @pidx:	Port index of peer device.
+ * @sidx:	Scratchpad index.
  * @val:	Scratchpad value.
  *
  * Write the value to the peer scratchpad register.
  *
  * Return: Zero on success, otherwise an error number.
  */
-static inline int ntb_peer_spad_write(struct ntb_dev *ntb, int idx, u32 val)
+static inline int ntb_peer_spad_write(struct ntb_dev *ntb, int pidx, int sidx,
+				      u32 val)
 {
-	return ntb->ops->peer_spad_write(ntb, idx, val);
+	if (!ntb->ops->peer_spad_write)
+		return -EINVAL;
+
+	return ntb->ops->peer_spad_write(ntb, pidx, sidx, val);
 }
 
 #endif