[edk2-devel] [PATCH 2/4] OvmfPkg/VirtNorFlashDxe: clarify block write logic

["Gerd Hoffmann" <kraxel@redhat.com>]

Introduce Start and End variables to make it easier to follow the
logic and code flow.  Also replace the two NorFlashWriteBuffer calls
with a loop containing one call.

With the changes in place the code is able to handle updates larger
than two P30_MAX_BUFFER_SIZE_IN_BYTES blocks, even though the patch
does not actually change the size limit.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c | 31 +++++++++++++-------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
index cdc809d75e3d..90db12716a4c 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
@@ -560,13 +560,18 @@ NorFlashWriteSingleBlock (
     // If the destination bits are only changing from 1s to 0s we can just write.
     // After a block is erased all bits in the block is set to 1.
     // If any byte requires us to erase we just give up and rewrite all of it.
+    UINTN   Start, End;
+    UINT32  Index, Count;
+
+    Start = Offset & ~BOUNDARY_OF_32_WORDS;
+    End   = (Offset + *NumBytes + BOUNDARY_OF_32_WORDS) & ~BOUNDARY_OF_32_WORDS;
 
     // Read the old version of the data into the shadow buffer
     Status = NorFlashRead (
                Instance,
                Lba,
-               Offset & ~BOUNDARY_OF_32_WORDS,
-               (((Offset & BOUNDARY_OF_32_WORDS) + *NumBytes) | BOUNDARY_OF_32_WORDS) + 1,
+               Start,
+               End - Start,
                Instance->ShadowBuffer
                );
     if (EFI_ERROR (Status)) {
@@ -599,25 +604,19 @@ NorFlashWriteSingleBlock (
       goto Exit;
     }
 
-    Status = NorFlashWriteBuffer (
-               Instance,
-               BlockAddress + (Offset & ~BOUNDARY_OF_32_WORDS),
-               P30_MAX_BUFFER_SIZE_IN_BYTES,
-               Instance->ShadowBuffer
-               );
-    if (EFI_ERROR (Status)) {
-      goto Exit;
-    }
-
-    if ((*NumBytes + (Offset & BOUNDARY_OF_32_WORDS)) > P30_MAX_BUFFER_SIZE_IN_BYTES) {
-      BlockAddress += P30_MAX_BUFFER_SIZE_IN_BYTES;
-
+    for (Index = 0, Count = (End - Start) / P30_MAX_BUFFER_SIZE_IN_BYTES;
+         Index < Count;
+         Index++, BlockAddress += P30_MAX_BUFFER_SIZE_IN_BYTES)
+    {
       Status = NorFlashWriteBuffer (
                  Instance,
                  BlockAddress + (Offset & ~BOUNDARY_OF_32_WORDS),
                  P30_MAX_BUFFER_SIZE_IN_BYTES,
-                 Instance->ShadowBuffer + P30_MAX_BUFFER_SIZE_IN_BYTES
+                 Instance->ShadowBuffer + P30_MAX_BUFFER_SIZE_IN_BYTES * Index
                  );
+      if (EFI_ERROR (Status)) {
+        goto Exit;
+      }
     }
 
 Exit:
-- 
2.43.0



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