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hw/nvram: Avoid unnecessary Xilinx eFuse backstore write

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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>
This commit is contained in:
Tong Ho 2023-04-26 14:16:07 -07:00 committed by Peter Maydell
parent e60a7d0d4d
commit c2c1c4a35c
1 changed files with 9 additions and 2 deletions
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11
hw/nvram/xlnx-efuse.c
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@ -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) bool xlnx_efuse_set_bit(XlnxEFuse *s, unsigned int bit)
{ {
uint32_t set, *row;
if (efuse_ro_bits_find(s, bit)) { if (efuse_ro_bits_find(s, bit)) {
g_autofree char *path = object_get_canonical_path(OBJECT(s)); 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; return false;
} }
s->fuse32[bit / 32] |= 1 << (bit % 32); /* Avoid back-end write unless there is a real update */
efuse_bdrv_sync(s, bit); row = &s->fuse32[bit / 32];
set = 1 << (bit % 32);
if (!(set & *row)) {
*row |= set;
efuse_bdrv_sync(s, bit);
}
return true; return true;
} }