On Thu, Apr 27, 2023 at 10:31 AM Tong Ho <tong...@amd.com> wrote:
>
> 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...@amd.com>
Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>
Alistair
> ---
> hw/nvram/xlnx-efuse.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/hw/nvram/xlnx-efuse.c b/hw/nvram/xlnx-efuse.c
> index fdfffaab99..655c40b8d1 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;
> }
>
> --
> 2.25.1
>
>
