From 33379dcfc40ecebfe255aeb4256906641a9fbcb1 Mon Sep 17 00:00:00 2001
From: Kinsey Moore <kinsey.moore@oarcorp.com>
Date: Fri, 1 Mar 2024 15:39:27 -0600
Subject: bsps/shared/xnandpsu: Add opportunistic page cache

Add an opportunistic page cache to the xnandpsu driver since it does not
implement partial page reads and common filesystem access patterns
perform multiple reads from the same page. This has been seen to provide
a 10x speedup to read speeds and a 2x speedup on first initialization
when used with JFFS2.
---
 bsps/shared/dev/nand/xnandpsu.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

(limited to 'bsps/shared')

diff --git a/bsps/shared/dev/nand/xnandpsu.c b/bsps/shared/dev/nand/xnandpsu.c
index 65c58b7e9b..79025f3c04 100644
--- a/bsps/shared/dev/nand/xnandpsu.c
+++ b/bsps/shared/dev/nand/xnandpsu.c
@@ -244,6 +244,11 @@ s32 XNandPsu_CfgInitialize(XNandPsu *InstancePtr, XNandPsu_Config *ConfigPtr,
 	InstancePtr->DmaMode = XNANDPSU_MDMA;
 	InstancePtr->IsReady = XIL_COMPONENT_IS_READY;
 
+#ifdef __rtems__
+	/* Set page cache to unavailable */
+	InstancePtr->PartialDataPageIndex = XNANDPSU_PAGE_CACHE_UNAVAILABLE;
+#endif
+
 	/* Initialize the NAND flash targets */
 	Status = XNandPsu_FlashInit(InstancePtr);
 	if (Status != XST_SUCCESS) {
@@ -278,6 +283,11 @@ s32 XNandPsu_CfgInitialize(XNandPsu *InstancePtr, XNandPsu_Config *ConfigPtr,
 #endif
 		goto Out;
 	}
+
+#ifdef __rtems__
+	/* Set page cache to none */
+	InstancePtr->PartialDataPageIndex = XNANDPSU_PAGE_CACHE_NONE;
+#endif
 Out:
 	return Status;
 }
@@ -1454,6 +1464,12 @@ s32 XNandPsu_Write(XNandPsu *InstancePtr, u64 Offset, u64 Length, u8 *SrcBuf)
 		goto Out;
 	}
 
+#ifdef __rtems__
+	if (InstancePtr->PartialDataPageIndex != XNANDPSU_PAGE_CACHE_UNAVAILABLE) {
+		/* All writes invalidate the page cache */
+		InstancePtr->PartialDataPageIndex = XNANDPSU_PAGE_CACHE_NONE;
+	}
+#endif
 	while (LengthVar > 0U) {
 		Block = (u32) (OffsetVar/InstancePtr->Geometry.BlockSize);
 		/*
@@ -1619,9 +1635,34 @@ s32 XNandPsu_Read(XNandPsu *InstancePtr, u64 Offset, u64 Length, u8 *DestBuf)
 					InstancePtr->Geometry.BytesPerPage :
 					(u32)LengthVar;
 		}
+#ifdef __rtems__
+		if (Page == InstancePtr->PartialDataPageIndex) {
+			/*
+			 * This is a whole page read for the currently cached
+			 * page. It will not be taken care of below, so perform
+			 * the copy here.
+			 */
+			if (PartialBytes == 0U) {
+				(void)Xil_MemCpy(DestBufPtr,
+						&InstancePtr->PartialDataBuf[0],
+						NumBytes);
+			}
+		} else {
+#endif
 		/* Read page */
 		Status = XNandPsu_ReadPage(InstancePtr, Target, Page, 0U,
 								BufPtr);
+#ifdef __rtems__
+			if (PartialBytes > 0U &&
+				InstancePtr->PartialDataPageIndex != XNANDPSU_PAGE_CACHE_UNAVAILABLE) {
+				/*
+				 * Partial read into page cache. Update the
+				 * cached page index.
+				 */
+				InstancePtr->PartialDataPageIndex = Page;
+			}
+		}
+#endif
 		if (Status != XST_SUCCESS) {
 			goto Out;
 		}
-- 
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