riscv: implement cache-management errata for T-Head SoCs

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.

Reviewed-by: Samuel Holland <samuel@sholland.org>
Tested-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220706231536.2041855-5-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
index b37b6fedd53b..202c83f677b2 100644
--- a/arch/riscv/errata/thead/errata.c
+++ b/arch/riscv/errata/thead/errata.c
@@ -27,6 +27,23 @@ static bool errata_probe_pbmt(unsigned int stage,
 	return false;
 }
 
+static bool errata_probe_cmo(unsigned int stage,
+			     unsigned long arch_id, unsigned long impid)
+{
+#ifdef CONFIG_ERRATA_THEAD_CMO
+	if (arch_id != 0 || impid != 0)
+		return false;
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return false;
+
+	riscv_noncoherent_supported();
+	return true;
+#else
+	return false;
+#endif
+}
+
 static u32 thead_errata_probe(unsigned int stage,
 			      unsigned long archid, unsigned long impid)
 {
@@ -35,6 +52,9 @@ static u32 thead_errata_probe(unsigned int stage,
 	if (errata_probe_pbmt(stage, archid, impid))
 		cpu_req_errata |= (1U << ERRATA_THEAD_PBMT);
 
+	if (errata_probe_cmo(stage, archid, impid))
+		cpu_req_errata |= (1U << ERRATA_THEAD_CMO);
+
 	return cpu_req_errata;
 }