[PATCH 4/6] lib: sbi: Allow forceful queueing of data in sbi_fifo_enqueue()

[Anup Patel]

Extend sbi_fifo_enqueue() to allow forceful queueing by droping
data from the tail.

Signed-off-by: Anup Patel <apatel at ventanamicro.com>
---
 include/sbi/sbi_fifo.h |  2 +-
 lib/sbi/sbi_fifo.c     | 69 +++++++++++++++++++++++++-----------------
 lib/sbi/sbi_sse.c      |  2 +-
 lib/sbi/sbi_tlb.c      |  3 +-
 4 files changed, 45 insertions(+), 31 deletions(-)

diff --git a/include/sbi/sbi_fifo.h b/include/sbi/sbi_fifo.h
index 1a85f07..af1632a 100644
--- a/include/sbi/sbi_fifo.h
+++ b/include/sbi/sbi_fifo.h
@@ -30,7 +30,7 @@ enum sbi_fifo_inplace_update_types {
 };
 
 int sbi_fifo_dequeue(struct sbi_fifo *fifo, void *data);
-int sbi_fifo_enqueue(struct sbi_fifo *fifo, void *data);
+int sbi_fifo_enqueue(struct sbi_fifo *fifo, void *data, bool force);
 void sbi_fifo_init(struct sbi_fifo *fifo, void *queue_mem, u16 entries,
 		   u16 entry_size);
 int sbi_fifo_is_empty(struct sbi_fifo *fifo);
diff --git a/lib/sbi/sbi_fifo.c b/lib/sbi/sbi_fifo.c
index 9199a30..d07ebff 100644
--- a/lib/sbi/sbi_fifo.c
+++ b/lib/sbi/sbi_fifo.c
@@ -90,6 +90,39 @@ static inline void  __sbi_fifo_enqueue(struct sbi_fifo *fifo, void *data)
 	fifo->avail++;
 }
 
+/* Note: must be called with fifo->qlock held */
+static inline void  __sbi_fifo_dequeue(struct sbi_fifo *fifo, void *data)
+{
+	if (!data)
+		goto skip_data_copy;
+
+	switch (fifo->entry_size) {
+	case 1:
+		*(char *)data = *(char *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
+		break;
+	case 2:
+		*(u16 *)data = *(u16 *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
+		break;
+	case 4:
+		*(u32 *)data = *(u32 *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
+		break;
+#if __riscv_xlen > 32
+	case 8:
+		*(u64 *)data = *(u64 *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
+		break;
+#endif
+	default:
+		sbi_memcpy(data, fifo->queue + (u32)fifo->tail * fifo->entry_size,
+			   fifo->entry_size);
+		break;
+	}
+
+skip_data_copy:
+	fifo->avail--;
+	fifo->tail++;
+	if (fifo->tail >= fifo->num_entries)
+		fifo->tail = 0;
+}
 
 /* Note: must be called with fifo->qlock held */
 static inline bool __sbi_fifo_is_empty(struct sbi_fifo *fifo)
@@ -173,7 +206,7 @@ int sbi_fifo_inplace_update(struct sbi_fifo *fifo, void *in,
 	return ret;
 }
 
-int sbi_fifo_enqueue(struct sbi_fifo *fifo, void *data)
+int sbi_fifo_enqueue(struct sbi_fifo *fifo, void *data, bool force)
 {
 	if (!fifo || !data)
 		return SBI_EINVAL;
@@ -181,9 +214,13 @@ int sbi_fifo_enqueue(struct sbi_fifo *fifo, void *data)
 	spin_lock(&fifo->qlock);
 
 	if (__sbi_fifo_is_full(fifo)) {
-		spin_unlock(&fifo->qlock);
-		return SBI_ENOSPC;
+		if (!force) {
+			spin_unlock(&fifo->qlock);
+			return SBI_ENOSPC;
+		}
+		__sbi_fifo_dequeue(fifo, NULL);
 	}
+
 	__sbi_fifo_enqueue(fifo, data);
 
 	spin_unlock(&fifo->qlock);
@@ -203,31 +240,7 @@ int sbi_fifo_dequeue(struct sbi_fifo *fifo, void *data)
 		return SBI_ENOENT;
 	}
 
-	switch (fifo->entry_size) {
-	case 1:
-		*(char *)data = *(char *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
-		break;
-	case 2:
-		*(u16 *)data = *(u16 *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
-		break;
-	case 4:
-		*(u32 *)data = *(u32 *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
-		break;
-#if __riscv_xlen > 32
-	case 8:
-		*(u64 *)data = *(u64 *)(fifo->queue + (u32)fifo->tail * fifo->entry_size);
-		break;
-#endif
-	default:
-		sbi_memcpy(data, fifo->queue + (u32)fifo->tail * fifo->entry_size,
-			   fifo->entry_size);
-		break;
-	}
-
-	fifo->avail--;
-	fifo->tail++;
-	if (fifo->tail >= fifo->num_entries)
-		fifo->tail = 0;
+	__sbi_fifo_dequeue(fifo, data);
 
 	spin_unlock(&fifo->qlock);
 
diff --git a/lib/sbi/sbi_sse.c b/lib/sbi/sbi_sse.c
index e39963f..fe36a64 100644
--- a/lib/sbi/sbi_sse.c
+++ b/lib/sbi/sbi_sse.c
@@ -667,7 +667,7 @@ static int sse_ipi_inject_send(unsigned long hartid, uint32_t event_id)
 	sse_inject_fifo_r =
 		sbi_scratch_offset_ptr(remote_scratch, sse_inject_fifo_off);
 
-	ret = sbi_fifo_enqueue(sse_inject_fifo_r, &evt);
+	ret = sbi_fifo_enqueue(sse_inject_fifo_r, &evt, false);
 	if (ret)
 		return SBI_EFAIL;
 
diff --git a/lib/sbi/sbi_tlb.c b/lib/sbi/sbi_tlb.c
index cca319f..01b31f4 100644
--- a/lib/sbi/sbi_tlb.c
+++ b/lib/sbi/sbi_tlb.c
@@ -351,7 +351,8 @@ static int tlb_update(struct sbi_scratch *scratch,
 
 	ret = sbi_fifo_inplace_update(tlb_fifo_r, data, tlb_update_cb);
 
-	if (ret == SBI_FIFO_UNCHANGED && sbi_fifo_enqueue(tlb_fifo_r, data) < 0) {
+	if (ret == SBI_FIFO_UNCHANGED &&
+	    sbi_fifo_enqueue(tlb_fifo_r, data, false) < 0) {
 		/**
 		 * For now, Busy loop until there is space in the fifo.
 		 * There may be case where target hart is also
-- 
2.34.1