riscv: sifive: Add SiFive alternative ports

Add required ports of the Alternative scheme for SiFive.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/Kconfig.erratas

@@ -9,4 +9,14 @@ config RISCV_ERRATA_ALTERNATIVE
 	  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

arch/riscv/Kconfig.socs

@@ -7,6 +7,7 @@ config SOC_SIFIVE
 	select CLK_SIFIVE
 	select CLK_SIFIVE_PRCI
 	select SIFIVE_PLIC
+	select ERRATA_SIFIVE
 	help
 	  This enables support for SiFive SoC platform hardware.
 

arch/riscv/errata/Makefile

@@ -1 +1,2 @@
 obj-y	+= alternative.o
+obj-$(CONFIG_ERRATA_SIFIVE) += sifive/

arch/riscv/errata/alternative.c

@@ -42,6 +42,11 @@ static void __init init_alternative(void)
 	riscv_fill_cpu_mfr_info();
 
 	switch (cpu_mfr_info.vendor_id) {
+#ifdef CONFIG_ERRATA_SIFIVE
+	case SIFIVE_VENDOR_ID:
+		vendor_patch_func = sifive_errata_patch_func;
+		break;
+#endif
 	default:
 		vendor_patch_func = NULL;
 	}

arch/riscv/errata/sifive/Makefile

@@ -0,0 +1 @@
+obj-y += errata.o

arch/riscv/errata/sifive/errata.c

@@ -0,0 +1,68 @@
+// 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);
+}

arch/riscv/include/asm/alternative.h

@@ -32,5 +32,8 @@ struct errata_checkfunc_id {
 	bool (*func)(struct alt_entry *alt);
 };
 
+void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+			      unsigned long archid, unsigned long impid);
+
 #endif
 #endif