Introduce 'Start' and 'End' variables to make it easier to follow the
logic and code flow. Also add a ascii art diagram (based on a
suggestion by Laszlo).
This also fixes the 'Size' calculation for the NorFlashRead() call.
Without this patch the code will read only one instead of two
P30_MAX_BUFFER_SIZE_IN_BYTES blocks in case '*NumBytes' is smaller than
P30_MAX_BUFFER_SIZE_IN_BYTES but 'Offset + *NumBytes' is not, i.e. the
update range crosses a P30_MAX_BUFFER_SIZE_IN_BYTES boundary.
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
Reviewed-by: Laszlo Ersek <ler...@redhat.com>
---
OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c | 36 ++++++++++++++++++++------
1 file changed, 28 insertions(+), 8 deletions(-)
diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
index 7f4743b00399..88a4d2c23fc0 100644
--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
@@ -520,6 +520,7 @@ NorFlashWriteSingleBlock (
UINTN BlockSize;
UINTN BlockAddress;
UINT8 *OrigData;
+ UINTN Start, End;
DEBUG ((DEBUG_BLKIO, "NorFlashWriteSingleBlock(Parameters: Lba=%ld,
Offset=0x%x, *NumBytes=0x%x, Buffer @ 0x%08x)\n", Lba, Offset, *NumBytes,
Buffer));
@@ -555,7 +556,28 @@ NorFlashWriteSingleBlock (
// To avoid pathological cases were a 2 byte write is disregarded because it
// occurs right at a 128 byte buffered write alignment boundary, permit up to
// twice the max buffer size, and perform two writes if needed.
- if ((*NumBytes + (Offset & BOUNDARY_OF_32_WORDS)) <= (2 *
P30_MAX_BUFFER_SIZE_IN_BYTES)) {
+ //
+ // 0 128 256
+ // [----------------|----------------]
+ // ^ ^ ^ ^
+ // | | | |
+ // | | | End, the next "word" boundary beyond
+ // | | | the (logical) update
+ // | | |
+ // | | (Offset & BOUNDARY_OF_32_WORDS) + NumBytes;
+ // | | i.e., the relative offset inside (or just past)
+ // | | the *double-word* such that it is the
+ // | | *exclusive* end of the (logical) update.
+ // | |
+ // | Offset & BOUNDARY_OF_32_WORDS; i.e., Offset within the
"word";
+ // | this is where the (logical) update is supposed to start
+ // |
+ // Start = Offset & ~BOUNDARY_OF_32_WORDS; i.e., Offset truncated to
"word" boundary
+
+ Start = Offset & ~BOUNDARY_OF_32_WORDS;
+ End = ALIGN_VALUE (Offset + *NumBytes, P30_MAX_BUFFER_SIZE_IN_BYTES);
+
+ if ((End - Start) <= (2 * P30_MAX_BUFFER_SIZE_IN_BYTES)) {
// Check to see if we need to erase before programming the data into NOR.
// 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.
@@ -565,8 +587,8 @@ NorFlashWriteSingleBlock (
Status = NorFlashRead (
Instance,
Lba,
- Offset & ~BOUNDARY_OF_32_WORDS,
- (*NumBytes | BOUNDARY_OF_32_WORDS) + 1,
+ Start,
+ End - Start,
Instance->ShadowBuffer
);
if (EFI_ERROR (Status)) {
@@ -601,7 +623,7 @@ NorFlashWriteSingleBlock (
Status = NorFlashWriteBuffer (
Instance,
- BlockAddress + (Offset & ~BOUNDARY_OF_32_WORDS),
+ BlockAddress + Start,
P30_MAX_BUFFER_SIZE_IN_BYTES,
Instance->ShadowBuffer
);
@@ -609,12 +631,10 @@ NorFlashWriteSingleBlock (
goto Exit;
}
- if ((*NumBytes + (Offset & BOUNDARY_OF_32_WORDS)) >
P30_MAX_BUFFER_SIZE_IN_BYTES) {
- BlockAddress += P30_MAX_BUFFER_SIZE_IN_BYTES;
-
+ if ((End - Start) > P30_MAX_BUFFER_SIZE_IN_BYTES) {
Status = NorFlashWriteBuffer (
Instance,
- BlockAddress + (Offset & ~BOUNDARY_OF_32_WORDS),
+ BlockAddress + Start + P30_MAX_BUFFER_SIZE_IN_BYTES,
P30_MAX_BUFFER_SIZE_IN_BYTES,
Instance->ShadowBuffer + P30_MAX_BUFFER_SIZE_IN_BYTES
);
--
2.43.0
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