[PATCH v3 3/5] riscv: errata: Add init framework for picoheart errata

["Yicong Yang" <yang.yicong@picoheart.com>]

Add init framework for handling upcoming picoheart erratas.

Signed-off-by: Yicong Yang <yang.yicong@picoheart.com>
---
 arch/riscv/Kconfig.errata                    | 10 ++++
 arch/riscv/errata/Makefile                   |  1 +
 arch/riscv/errata/picoheart/Makefile         |  5 ++
 arch/riscv/errata/picoheart/errata.c         | 57 ++++++++++++++++++++
 arch/riscv/include/asm/alternative.h         |  3 ++
 arch/riscv/include/asm/errata_list_vendors.h |  4 ++
 arch/riscv/include/asm/vendorid_list.h       |  1 +
 arch/riscv/kernel/alternative.c              |  5 ++
 8 files changed, 86 insertions(+)
 create mode 100644 arch/riscv/errata/picoheart/Makefile
 create mode 100644 arch/riscv/errata/picoheart/errata.c

diff --git a/arch/riscv/Kconfig.errata b/arch/riscv/Kconfig.errata
index 3c945d086c7d..374d7fcf7936 100644
--- a/arch/riscv/Kconfig.errata
+++ b/arch/riscv/Kconfig.errata
@@ -154,4 +154,14 @@ config ERRATA_THEAD_GHOSTWRITE
 
 	  If you don't know what to do here, say "Y".
 
+config ERRATA_PICOHEART
+	bool "Picoheart errata"
+	depends on RISCV_ALTERNATIVE
+	help
+	  All Picoheart errata Kconfig depend on this Kconfig. Disabling
+	  this Kconfig will disable all Picoheart errata. Please say "Y"
+	  here if your platform uses Picoheart CPU cores.
+
+	  Otherwise, please say "N" here to avoid unnecessary overhead.
+
 endmenu # "CPU errata selection"
diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index 02a7a3335b1d..a36c5ce1ce7b 100644
--- a/arch/riscv/errata/Makefile
+++ b/arch/riscv/errata/Makefile
@@ -16,3 +16,4 @@ obj-$(CONFIG_ERRATA_ANDES) += andes/
 obj-$(CONFIG_ERRATA_MIPS) += mips/
 obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
 obj-$(CONFIG_ERRATA_THEAD) += thead/
+obj-$(CONFIG_ERRATA_PICOHEART) += picoheart/
diff --git a/arch/riscv/errata/picoheart/Makefile b/arch/riscv/errata/picoheart/Makefile
new file mode 100644
index 000000000000..6278c389b801
--- /dev/null
+++ b/arch/riscv/errata/picoheart/Makefile
@@ -0,0 +1,5 @@
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+CFLAGS_errata.o := -mcmodel=medany
+endif
+
+obj-y += errata.o
diff --git a/arch/riscv/errata/picoheart/errata.c b/arch/riscv/errata/picoheart/errata.c
new file mode 100644
index 000000000000..53b690878f78
--- /dev/null
+++ b/arch/riscv/errata/picoheart/errata.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2026 Picoheart (SG) Pte. Ltd.
+ *
+ * Author: Yicong Yang <yang.yicong@picoheart.com>
+ */
+
+#include <linux/cacheflush.h>
+#include <linux/cleanup.h>
+#include <linux/kernel.h>
+#include <linux/memory.h>
+#include <linux/string.h>
+#include <asm/alternative.h>
+#include <asm/errata_list.h>
+#include <asm/text-patching.h>
+#include <asm/vendor_extensions.h>
+#include <asm/vendorid_list.h>
+
+static u32 picoheart_errata_probe(unsigned int stage, unsigned long archid,
+				  unsigned long impid)
+{
+	return 0;
+}
+
+void picoheart_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+				 unsigned long archid, unsigned long impid,
+				 unsigned int stage)
+{
+	u32 cpu_req_errata = picoheart_errata_probe(stage, archid, impid);
+	struct alt_entry *alt;
+	void *oldptr, *altptr;
+	u32 tmp;
+
+	BUILD_BUG_ON(ERRATA_PICOHEART_NUMBER >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
+
+	for (alt = begin; alt < end; alt++) {
+		if (alt->vendor_id != PICOHEART_VENDOR_ID ||
+		    alt->patch_id >= ERRATA_PICOHEART_NUMBER)
+			continue;
+
+		tmp = (1U << alt->patch_id);
+		if (cpu_req_errata & tmp) {
+			oldptr = ALT_OLD_PTR(alt);
+			altptr = ALT_ALT_PTR(alt);
+
+			if (stage == RISCV_ALTERNATIVES_EARLY_BOOT) {
+				memcpy(oldptr, altptr, alt->alt_len);
+			} else {
+				guard(mutex)(&text_mutex);
+				patch_text_nosync(oldptr, altptr, alt->alt_len);
+			}
+		}
+	}
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		local_flush_icache_all();
+}
diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
index 8407d1d535b8..57298f21bb70 100644
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -57,6 +57,9 @@ void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
 void thead_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
 			     unsigned long archid, unsigned long impid,
 			     unsigned int stage);
+void picoheart_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+				 unsigned long archid, unsigned long impid,
+				 unsigned int stage);
 
 void riscv_cpufeature_patch_func(struct alt_entry *begin, struct alt_entry *end,
 				 unsigned int stage);
diff --git a/arch/riscv/include/asm/errata_list_vendors.h b/arch/riscv/include/asm/errata_list_vendors.h
index ec7eba373437..958e4f4624f7 100644
--- a/arch/riscv/include/asm/errata_list_vendors.h
+++ b/arch/riscv/include/asm/errata_list_vendors.h
@@ -26,4 +26,8 @@
 #define	ERRATA_MIPS_NUMBER 1
 #endif
 
+#ifdef CONFIG_ERRATA_PICOHEART
+#define ERRATA_PICOHEART_NUMBER	0
+#endif
+
 #endif /* ASM_ERRATA_LIST_VENDORS_H */
diff --git a/arch/riscv/include/asm/vendorid_list.h b/arch/riscv/include/asm/vendorid_list.h
index 7f5030ee1fcf..1ea6d00eb61a 100644
--- a/arch/riscv/include/asm/vendorid_list.h
+++ b/arch/riscv/include/asm/vendorid_list.h
@@ -10,5 +10,6 @@
 #define MIPS_VENDOR_ID		0x127
 #define SIFIVE_VENDOR_ID	0x489
 #define THEAD_VENDOR_ID		0x5b7
+#define PICOHEART_VENDOR_ID     0x77d
 
 #endif
diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index c0c9306022c5..44c62932fb27 100644
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -61,6 +61,11 @@ static void riscv_fill_cpu_mfr_info(struct cpu_manufacturer_info_t *cpu_mfr_info
 	case THEAD_VENDOR_ID:
 		cpu_mfr_info->patch_func = thead_errata_patch_func;
 		break;
+#endif
+#ifdef CONFIG_ERRATA_PICOHEART
+	case PICOHEART_VENDOR_ID:
+		cpu_mfr_info->patch_func = picoheart_errata_patch_func;
+		break;
 #endif
 	default:
 		cpu_mfr_info->patch_func = NULL;
-- 
2.50.1 (Apple Git-155)

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