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66 lines
3.0 KiB
66 lines
3.0 KiB
9 months ago
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From 0193a89b0db837da31301bc1edb8382927842978 Mon Sep 17 00:00:00 2001
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From: Gerd Hoffmann <kraxel@redhat.com>
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Date: Tue, 16 Jan 2024 18:11:03 +0100
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Subject: [PATCH 14/18] OvmfPkg/VirtNorFlashDxe: allow larger writes without
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block erase
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RH-Author: Gerd Hoffmann <None>
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RH-MergeRequest: 43: OvmfPkg/VirtNorFlashDxe backport
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RH-Jira: RHEL-17587
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Commit: [16/20] 27ac63b90eb5e6fdc00cbc5a9105c3178ee559cd
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Raise the limit for writes without block erase from two to four
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P30_MAX_BUFFER_SIZE_IN_BYTES blocks. With this in place almost all efi
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variable updates are handled without block erase. With the old limit
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some variable updates (with device paths) took the block erase code
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path.
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Reviewed-by: Laszlo Ersek <lersek@redhat.com>
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Message-Id: <20240116171105.37831-5-kraxel@redhat.com>
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(cherry picked from commit b25733c97442513890ae6bb8e10fd340f13844a7)
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---
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OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c | 18 ++++++++++--------
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1 file changed, 10 insertions(+), 8 deletions(-)
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diff --git a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
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index 3d1343b381..3d1d20daa1 100644
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--- a/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
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+++ b/OvmfPkg/VirtNorFlashDxe/VirtNorFlash.c
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@@ -550,13 +550,15 @@ NorFlashWriteSingleBlock (
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return EFI_BAD_BUFFER_SIZE;
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}
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- // Pick P30_MAX_BUFFER_SIZE_IN_BYTES (== 128 bytes) as a good start for word
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- // operations as opposed to erasing the block and writing the data regardless
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- // if an erase is really needed. It looks like most individual NV variable
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- // writes are smaller than 128 bytes.
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- // To avoid pathological cases were a 2 byte write is disregarded because it
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- // occurs right at a 128 byte buffered write alignment boundary, permit up to
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- // twice the max buffer size, and perform two writes if needed.
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+ // Pick 4 * P30_MAX_BUFFER_SIZE_IN_BYTES (== 512 bytes) as a good
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+ // start for word operations as opposed to erasing the block and
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+ // writing the data regardless if an erase is really needed.
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+ //
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+ // Many NV variable updates are small enough for a a single
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+ // P30_MAX_BUFFER_SIZE_IN_BYTES block write. In case the update is
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+ // larger than a single block, or the update crosses a
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+ // P30_MAX_BUFFER_SIZE_IN_BYTES boundary (as shown in the diagram
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+ // below), or both, we might have to write two or more blocks.
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//
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// 0 128 256
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// [----------------|----------------]
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@@ -578,7 +580,7 @@ NorFlashWriteSingleBlock (
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Start = Offset & ~BOUNDARY_OF_32_WORDS;
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End = ALIGN_VALUE (Offset + *NumBytes, P30_MAX_BUFFER_SIZE_IN_BYTES);
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- if ((End - Start) <= (2 * P30_MAX_BUFFER_SIZE_IN_BYTES)) {
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+ if ((End - Start) <= (4 * P30_MAX_BUFFER_SIZE_IN_BYTES)) {
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// Check to see if we need to erase before programming the data into NOR.
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// If the destination bits are only changing from 1s to 0s we can just write.
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// After a block is erased all bits in the block is set to 1.
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--
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2.41.0
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