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| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2015-02-28 20:33:34 +0000 |
|---|---|---|
| committer | lersek <lersek@Edk2> | 2015-02-28 20:33:34 +0000 |
| commit | e482753b334b03f297a9655caf775bd8469ab91c (patch) | |
| tree | e21a8e24992a3ef8307d31721efac4fe9a733eda /OvmfPkg/XenBusDxe/TestAndClearBit.c | |
| parent | b94c3ac93d57cf2711814932bf082b2ce496eb82 (diff) | |
| download | edk2-e482753b334b03f297a9655caf775bd8469ab91c.tar.gz edk2-e482753b334b03f297a9655caf775bd8469ab91c.tar.bz2 edk2-e482753b334b03f297a9655caf775bd8469ab91c.zip | |
Ovmf/Xen: port XenBusDxe to other architectures
This patch updates XenBusDxe to use the 16-bit compare and exchange
function that was introduced for this purpose to the
BaseSynchronizationLib. It also provides a new generic implementation
of TestAndClearBit () using the same 16-bit compare and exchange, making
this module fully architecture agnostic.
Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16975 6f19259b-4bc3-4df7-8a09-765794883524
Diffstat (limited to 'OvmfPkg/XenBusDxe/TestAndClearBit.c')
| -rw-r--r-- | OvmfPkg/XenBusDxe/TestAndClearBit.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/OvmfPkg/XenBusDxe/TestAndClearBit.c b/OvmfPkg/XenBusDxe/TestAndClearBit.c new file mode 100644 index 0000000000..410677ee8a --- /dev/null +++ b/OvmfPkg/XenBusDxe/TestAndClearBit.c @@ -0,0 +1,45 @@ +/** @file
+ Implementation of TestAndClearBit using compare-exchange primitive
+
+ Copyright (C) 2015, Linaro Ltd.
+
+ This program and the accompanying materials
+ are licensed and made available under the terms and conditions of the BSD License
+ which accompanies this distribution. The full text of the license may be found at
+ http://opensource.org/licenses/bsd-license.php
+
+ THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include <Base.h>
+#include <Library/SynchronizationLib.h>
+
+INT32
+EFIAPI
+TestAndClearBit (
+ IN INT32 Bit,
+ IN VOID *Address
+ )
+{
+ UINT16 Word, Read;
+ UINT16 Mask;
+
+ //
+ // Calculate the effective address relative to 'Address' based on the
+ // higher order bits of 'Bit'. Use signed shift instead of division to
+ // ensure we round towards -Inf, and end up with a positive shift in
+ // 'Bit', even if 'Bit' itself is negative.
+ //
+ Address += (Bit >> 4) * sizeof(UINT16);
+ Mask = 1U << (Bit & 15);
+
+ for (Word = *(UINT16 *) Address; Word & Mask; Word = Read) {
+ Read = InterlockedCompareExchange16 (Address, Word, Word & ~Mask);
+ if (Read == Word) {
+ return 1;
+ }
+ }
+ return 0;
+}
|