aboutsummaryrefslogtreecommitdiff
path: root/hw
diff options
context:
space:
mode:
authorTong Ho <tong.ho@amd.com>2023-04-26 14:16:07 -0700
committerPeter Maydell <peter.maydell@linaro.org>2023-07-17 11:05:52 +0100
commitc2c1c4a35c7c2b1a4140b0942b9797c857e476a4 (patch)
tree83c0c79893044cb23d374180c3fee16195fc95df /hw
parente60a7d0d4d89c8bca8a74a877e31abce50e848e3 (diff)
downloadqemu-c2c1c4a35c7c2b1a4140b0942b9797c857e476a4.zip
qemu-c2c1c4a35c7c2b1a4140b0942b9797c857e476a4.tar.gz
qemu-c2c1c4a35c7c2b1a4140b0942b9797c857e476a4.tar.bz2
hw/nvram: Avoid unnecessary Xilinx eFuse backstore write
Add a check in the bit-set operation to write the backstore only if the affected bit is 0 before. With this in place, there will be no need for callers to do the checking in order to avoid unnecessary writes. Signed-off-by: Tong Ho <tong.ho@amd.com> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'hw')
-rw-r--r--hw/nvram/xlnx-efuse.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/hw/nvram/xlnx-efuse.c b/hw/nvram/xlnx-efuse.c
index fdfffaa..655c40b 100644
--- a/hw/nvram/xlnx-efuse.c
+++ b/hw/nvram/xlnx-efuse.c
@@ -143,6 +143,8 @@ static bool efuse_ro_bits_find(XlnxEFuse *s, uint32_t k)
bool xlnx_efuse_set_bit(XlnxEFuse *s, unsigned int bit)
{
+ uint32_t set, *row;
+
if (efuse_ro_bits_find(s, bit)) {
g_autofree char *path = object_get_canonical_path(OBJECT(s));
@@ -152,8 +154,13 @@ bool xlnx_efuse_set_bit(XlnxEFuse *s, unsigned int bit)
return false;
}
- s->fuse32[bit / 32] |= 1 << (bit % 32);
- efuse_bdrv_sync(s, bit);
+ /* Avoid back-end write unless there is a real update */
+ row = &s->fuse32[bit / 32];
+ set = 1 << (bit % 32);
+ if (!(set & *row)) {
+ *row |= set;
+ efuse_bdrv_sync(s, bit);
+ }
return true;
}