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author | Gerd Hoffmann <kraxel@redhat.com> | 2024-01-16 18:11:01 +0100 |
---|---|---|
committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2024-01-18 19:25:14 +0000 |
commit | 35d8ea8097794b522149688b5cfaf8364bc44d54 (patch) | |
tree | b261f67dbdebbcfb36f078a376221067b7e901c4 /OvmfPkg | |
parent | 0395045ae307c43a41f72ca9a8bf4eb8f16b2fe0 (diff) | |
download | edk2-35d8ea8097794b522149688b5cfaf8364bc44d54.zip edk2-35d8ea8097794b522149688b5cfaf8364bc44d54.tar.gz edk2-35d8ea8097794b522149688b5cfaf8364bc44d54.tar.bz2 |
OvmfPkg/VirtNorFlashDxe: clarify block write logic & fix shadowbuffer reads
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 <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20240116171105.37831-3-kraxel@redhat.com>
Diffstat (limited to 'OvmfPkg')
-rw-r--r-- | OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c | 36 |
1 files changed, 28 insertions, 8 deletions
diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c index 7f4743b..88a4d2c 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
);
|