[PATCH 2/2] riscv: implement cache-management errata for T-Head SoCs

[Heiko Stuebner]

The T-Head C906 and C910 implement a scheme for handling
cache operations different from the generic Zicbom extension.

Add an errata for it next to the generic dma coherency ops.

Signed-off-by: Heiko Stuebner <heiko at sntech.de>
---
 arch/riscv/Kconfig.erratas           | 10 +++++++
 arch/riscv/errata/thead/errata.c     |  5 ++++
 arch/riscv/include/asm/errata_list.h | 45 ++++++++++++++++++++++++++--
 3 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
index de4002baa1d0..89a6dcb8ac2a 100644
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -50,4 +50,14 @@ config ERRATA_THEAD_PBMT
 
 	  If you don't know what to do here, say "Y".
 
+config ERRATA_THEAD_CMO
+	bool "Apply T-Head cache management errata"
+	depends on ERRATA_THEAD && RISCV_DMA_NONCOHERENT
+	default y
+	help
+	  This will apply the cache management errata to handle the
+	  non-standard handling on non-coherent operations on T-Head SoCs.
+
+	  If you don't know what to do here, say "Y".
+
 endmenu
diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
index fd8e0538a3f0..11c26c37425f 100644
--- a/arch/riscv/errata/thead/errata.c
+++ b/arch/riscv/errata/thead/errata.c
@@ -33,6 +33,11 @@ static const struct errata_info errata_list[ERRATA_THEAD_NUMBER] = {
 		.stage = RISCV_ALTERNATIVES_EARLY_BOOT,
 		.check_func = errata_mt_check_func
 	},
+	{
+		.name = "cache-management",
+		.stage = RISCV_ALTERNATIVES_BOOT,
+		.check_func = errata_mt_check_func
+	},
 };
 
 static u32 thead_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid)
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index 7a2dd61af24d..f7c6805daeab 100644
--- a/arch/riscv/include/asm/errata_list.h
+++ b/arch/riscv/include/asm/errata_list.h
@@ -16,7 +16,8 @@
 
 #ifdef CONFIG_ERRATA_THEAD
 #define	ERRATA_THEAD_PBMT 0
-#define	ERRATA_THEAD_NUMBER 1
+#define	ERRATA_THEAD_CMO 1
+#define	ERRATA_THEAD_NUMBER 2
 #endif
 
 #define	CPUFEATURE_SVPBMT 0
@@ -104,8 +105,37 @@ asm volatile(ALTERNATIVE(								\
 #define CBO_CLEAN_A0	".long 0x25200F"
 #define CBO_FLUSH_A0	".long 0x05200F"
 
+/*
+ * dcache.ipa rs1 (invalidate, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01010      rs1       000      00000  0001011
+ * dache.iva rs1 (invalida, virtual address)
+ *   0000001    00110      rs1       000      00000  0001011
+ *
+ * dcache.cpa rs1 (clean, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01001      rs1       000      00000  0001011
+ * dcache.cva rs1 (clean, virtual address)
+ *   0000001    00100      rs1       000      00000  0001011
+ *
+ * dcache.cipa rs1 (clean then invalidate, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01011      rs1       000      00000  0001011
+ * dcache.civa rs1 (... virtual address)
+ *   0000001    00111      rs1       000      00000  0001011
+ *
+ * sync.s (make sure all cache operations finished)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000000    11001     00000      000      00000  0001011
+ */
+#define THEAD_INVAL_A0	".long 0x0265000b"
+#define THEAD_CLEAN_A0	".long 0x0245000b"
+#define THEAD_FLUSH_A0	".long 0x0275000b"
+#define THEAD_SYNC_S	".long 0x0190000b"
+
 #define ALT_CMO_OP(_op, _start, _size)							\
-asm volatile(ALTERNATIVE(								\
+asm volatile(ALTERNATIVE_2(								\
+	"nop\n\t"									\
 	"nop\n\t"									\
 	"nop\n\t"									\
 	"nop\n\t"									\
@@ -117,7 +147,16 @@ asm volatile(ALTERNATIVE(								\
 	CBO_##_op##_A0 "\n\t"								\
 	"addi a0, a0, %0\n\t"								\
 	"2:\n\t"									\
-	"bltu a0, %2, 3b\n\t", 0, CPUFEATURE_CMO, CONFIG_RISCV_DMA_NONCOHERENT)		\
+	"bltu a0, %2, 3b\n\t"								\
+	"nop", 0, CPUFEATURE_CMO, CONFIG_RISCV_DMA_NONCOHERENT,				\
+	"mv a0, %1\n\t"									\
+	"j 2f\n\t"									\
+	"3:\n\t"									\
+	THEAD_##_op##_A0 "\n\t"								\
+	"addi a0, a0, %0\n\t"								\
+	"2:\n\t"									\
+	"bltu a0, %2, 3b\n\t"								\
+	THEAD_SYNC_S, THEAD_VENDOR_ID, ERRATA_THEAD_CMO, CONFIG_ERRATA_THEAD_CMO)	\
 	: : "I"(L1_CACHE_BYTES), "r"((_start) & ~(L1_CACHE_BYTES - 1)),			\
 	    "r"(ALIGN((_start) + (_size), L1_CACHE_BYTES)))
 
-- 
2.30.2