[PATCH v8 3/7] riscv: errata: Add Andes alternative ports

[Prabhakar <prabhakar.csengg@gmail.com>]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

Add required ports of the Alternative scheme for Andes CPU cores.

I/O Coherence Port (IOCP) provides an AXI interface for connecting external
non-caching masters, such as DMA controllers. IOCP is a specification
option and is disabled on the Renesas RZ/Five SoC due to this reason cache
management needs a software workaround.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
---
v7 -> v8
* Now patching the code using patch_text_nosync() and riscv_alternative_fix_offsets()

v6 -> v7
* Renamed RZFIVE_SBI_EXT_IOCP_SW_WORKAROUND -> ANDES_SBI_EXT_IOCP_SW_WORKAROUND
* Dropped "depends on !XIP_KERNEL" for ERRATA_ANDES config

v5 -> v6
* Dropped patching alternative and now just probing IOCP

v4 -> v5
* Sorted the Kconfig/Makefile/Switch based on Core name
* Added a comments
* Introduced RZFIVE_SBI_EXT_IOCP_SW_WORKAROUND SBI EXT ID to check if
  CMO needs to be applied. Is there a way we can access the DTB while patching
  as we can drop this SBI EXT ID and add a DT property instead for cmo?

RFC v3 -> v4
* New patch
---
 arch/riscv/Kconfig.errata            |  21 ++++++
 arch/riscv/errata/Makefile           |   1 +
 arch/riscv/errata/andes/Makefile     |   1 +
 arch/riscv/errata/andes/errata.c     | 104 +++++++++++++++++++++++++++
 arch/riscv/include/asm/alternative.h |   3 +
 arch/riscv/include/asm/errata_list.h |   5 ++
 arch/riscv/kernel/alternative.c      |   5 ++
 7 files changed, 140 insertions(+)
 create mode 100644 arch/riscv/errata/andes/Makefile
 create mode 100644 arch/riscv/errata/andes/errata.c

diff --git a/arch/riscv/Kconfig.errata b/arch/riscv/Kconfig.errata
index 0c8f4652cd82..92c779764b27 100644
--- a/arch/riscv/Kconfig.errata
+++ b/arch/riscv/Kconfig.errata
@@ -1,5 +1,26 @@
 menu "CPU errata selection"
 
+config ERRATA_ANDES
+	bool "Andes AX45MP errata"
+	depends on RISCV_ALTERNATIVE
+	help
+	  All Andes errata Kconfig depend on this Kconfig. Disabling
+	  this Kconfig will disable all Andes errata. Please say "Y"
+	  here if your platform uses Andes CPU cores.
+
+	  Otherwise, please say "N" here to avoid unnecessary overhead.
+
+config ERRATA_ANDES_CMO
+	bool "Apply Andes cache management errata"
+	depends on ERRATA_ANDES && MMU && ARCH_R9A07G043
+	select RISCV_DMA_NONCOHERENT
+	default y
+	help
+	  This will apply the cache management errata to handle the
+	  non-standard handling on non-coherent operations on Andes cores.
+
+	  If you don't know what to do here, say "Y".
+
 config ERRATA_SIFIVE
 	bool "SiFive errata"
 	depends on RISCV_ALTERNATIVE
diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index a1055965fbee..6f1c693af92d 100644
--- a/arch/riscv/errata/Makefile
+++ b/arch/riscv/errata/Makefile
@@ -1,2 +1,3 @@
+obj-$(CONFIG_ERRATA_ANDES) += andes/
 obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
 obj-$(CONFIG_ERRATA_THEAD) += thead/
diff --git a/arch/riscv/errata/andes/Makefile b/arch/riscv/errata/andes/Makefile
new file mode 100644
index 000000000000..2d644e19caef
--- /dev/null
+++ b/arch/riscv/errata/andes/Makefile
@@ -0,0 +1 @@
+obj-y += errata.o
diff --git a/arch/riscv/errata/andes/errata.c b/arch/riscv/errata/andes/errata.c
new file mode 100644
index 000000000000..49315f36022e
--- /dev/null
+++ b/arch/riscv/errata/andes/errata.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Erratas to be applied for Andes CPU cores
+ *
+ *  Copyright (C) 2023 Renesas Electronics Corporation.
+ *
+ * Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
+ */
+
+#include <linux/memory.h>
+#include <linux/module.h>
+
+#include <asm/alternative.h>
+#include <asm/cacheflush.h>
+#include <asm/errata_list.h>
+#include <asm/patch.h>
+#include <asm/processor.h>
+#include <asm/sbi.h>
+#include <asm/vendorid_list.h>
+
+#define ANDESTECH_AX45MP_MARCHID	0x8000000000008a45UL
+#define ANDESTECH_AX45MP_MIMPID		0x500UL
+#define ANDESTECH_SBI_EXT_ANDES		0x0900031E
+
+#define ANDES_SBI_EXT_IOCP_SW_WORKAROUND	1
+
+static long ax45mp_iocp_sw_workaround(void)
+{
+	struct sbiret ret;
+
+	/*
+	 * ANDES_SBI_EXT_IOCP_SW_WORKAROUND SBI EXT checks if the IOCP is missing and
+	 * cache is controllable only then CMO will be applied to the platform.
+	 */
+	ret = sbi_ecall(ANDESTECH_SBI_EXT_ANDES, ANDES_SBI_EXT_IOCP_SW_WORKAROUND,
+			0, 0, 0, 0, 0, 0);
+
+	return ret.error ? 0 : ret.value;
+}
+
+static bool errata_probe_iocp(unsigned int stage, unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_ANDES_CMO))
+		return false;
+
+	if (arch_id != ANDESTECH_AX45MP_MARCHID || impid != ANDESTECH_AX45MP_MIMPID)
+		return false;
+
+	if (!ax45mp_iocp_sw_workaround())
+		return false;
+
+	/* Set this just to make core cbo code happy */
+	riscv_cbom_block_size = 1;
+	riscv_noncoherent_supported();
+
+	return true;
+}
+
+static u32 andes_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid)
+{
+	u32 cpu_req_errata = 0;
+
+	/*
+	 * In the absence of the I/O Coherency Port, access to certain peripherals
+	 * requires vendor specific DMA handling.
+	 */
+	if (errata_probe_iocp(stage, archid, impid))
+		cpu_req_errata |= BIT(ERRATA_ANDESTECH_NO_IOCP);
+
+	return cpu_req_errata;
+}
+
+void __init_or_module andes_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+					      unsigned long archid, unsigned long impid,
+					      unsigned int stage)
+{
+	u32 cpu_req_errata = andes_errata_probe(stage, archid, impid);
+	void *oldptr, *altptr;
+	struct alt_entry *alt;
+	u32 tmp;
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return;
+
+	for (alt = begin; alt < end; alt++) {
+		if (alt->vendor_id != ANDESTECH_VENDOR_ID)
+			continue;
+		if (alt->patch_id >= ERRATA_ANDESTECH_NUMBER)
+			continue;
+
+		tmp = BIT(alt->patch_id);
+		if (cpu_req_errata & tmp) {
+			oldptr = ALT_OLD_PTR(alt);
+			altptr = ALT_ALT_PTR(alt);
+
+			mutex_lock(&text_mutex);
+			patch_text_nosync(oldptr, altptr, alt->alt_len);
+
+			riscv_alternative_fix_offsets(oldptr, alt->alt_len,
+						      oldptr - altptr);
+			mutex_unlock(&text_mutex);
+		}
+	}
+}
diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
index 58ccd2f8cab7..3c2b59b25017 100644
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -45,6 +45,9 @@ struct alt_entry {
 	u32 patch_id;		/* The patch ID (erratum ID or cpufeature ID) */
 };
 
+void andes_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+			     unsigned long archid, unsigned long impid,
+			     unsigned int stage);
 void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
 			      unsigned long archid, unsigned long impid,
 			      unsigned int stage);
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index fb1a810f3d8c..e2ecd01bfac7 100644
--- a/arch/riscv/include/asm/errata_list.h
+++ b/arch/riscv/include/asm/errata_list.h
@@ -11,6 +11,11 @@
 #include <asm/hwcap.h>
 #include <asm/vendorid_list.h>
 
+#ifdef CONFIG_ERRATA_ANDES
+#define ERRATA_ANDESTECH_NO_IOCP	0
+#define ERRATA_ANDESTECH_NUMBER		1
+#endif
+
 #ifdef CONFIG_ERRATA_SIFIVE
 #define	ERRATA_SIFIVE_CIP_453 0
 #define	ERRATA_SIFIVE_CIP_1200 1
diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 2354c69dc7d1..8a34e72c2b5e 100644
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -42,6 +42,11 @@ static void __init_or_module riscv_fill_cpu_mfr_info(struct cpu_manufacturer_inf
 #endif
 
 	switch (cpu_mfr_info->vendor_id) {
+#ifdef CONFIG_ERRATA_ANDES
+	case ANDESTECH_VENDOR_ID:
+		cpu_mfr_info->patch_func = andes_errata_patch_func;
+		break;
+#endif
 #ifdef CONFIG_ERRATA_SIFIVE
 	case SIFIVE_VENDOR_ID:
 		cpu_mfr_info->patch_func = sifive_errata_patch_func;
-- 
2.25.1