From c2c1c4a35c7c2b1a4140b0942b9797c857e476a4 Mon Sep 17 00:00:00 2001 From: Tong Ho Date: Wed, 26 Apr 2023 14:16:07 -0700 Subject: [PATCH] hw/nvram: Avoid unnecessary Xilinx eFuse backstore write MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Alistair Francis Reviewed-by: Francisco Iglesias Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Peter Maydell --- 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; }