code patching is performed once in the boot stages. It means
that the overhead from this mechanism is just taken once.
+config ERRATA_SIFIVE
+ bool "SiFive errata"
+ depends on RISCV_ERRATA_ALTERNATIVE
+ help
+ All SiFive errata Kconfig depend on this Kconfig. Disabling
+ this Kconfig will disable all SiFive errata. Please say "Y"
+ here if your platform uses SiFive CPU cores.
+
+ Otherwise, please say "N" here to avoid unnecessary overhead.
+
endmenu
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Sifive.
+ */
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/bug.h>
+#include <asm/patch.h>
+#include <asm/alternative.h>
+#include <asm/vendorid_list.h>
+#include <asm/errata_list.h>
+
+struct errata_info_t {
+ char name[ERRATA_STRING_LENGTH_MAX];
+ bool (*check_func)(unsigned long arch_id, unsigned long impid);
+};
+
+static u32 __init sifive_errata_probe(unsigned long archid, unsigned long impid)
+{
+ int idx;
+ u32 cpu_req_errata = 0;
+
+ for (idx = 0; idx < ERRATA_SIFIVE_NUMBER; idx++)
+ if (errata_list[idx].check_func(archid, impid))
+ cpu_req_errata |= (1U << idx);
+
+ return cpu_req_errata;
+}
+
+static void __init warn_miss_errata(u32 miss_errata)
+{
+ int i;
+
+ pr_warn("----------------------------------------------------------------\n");
+ pr_warn("WARNING: Missing the following errata may cause potential issues\n");
+ for (i = 0; i < ERRATA_SIFIVE_NUMBER; i++)
+ if (miss_errata & 0x1 << i)
+ pr_warn("\tSiFive Errata[%d]:%s\n", i, errata_list[i].name);
+ pr_warn("Please enable the corresponding Kconfig to apply them\n");
+ pr_warn("----------------------------------------------------------------\n");
+}
+
+void __init sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+ unsigned long archid, unsigned long impid)
+{
+ struct alt_entry *alt;
+ u32 cpu_req_errata = sifive_errata_probe(archid, impid);
+ u32 cpu_apply_errata = 0;
+ u32 tmp;
+
+ for (alt = begin; alt < end; alt++) {
+ if (alt->vendor_id != SIFIVE_VENDOR_ID)
+ continue;
+ if (alt->errata_id >= ERRATA_SIFIVE_NUMBER) {
+ WARN(1, "This errata id:%d is not in kernel errata list", alt->errata_id);
+ continue;
+ }
+
+ tmp = (1U << alt->errata_id);
+ if (cpu_req_errata & tmp) {
+ patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
+ cpu_apply_errata |= tmp;
+ }
+ }
+ if (cpu_apply_errata != cpu_req_errata)
+ warn_miss_errata(cpu_req_errata - cpu_apply_errata);
+}