arch/riscv: add Kconfig variable RISCV_SOC_HAS_MENVCFG

Older parts do not have the menvcfg csr.
Provide a Kconfig variable, default y, to enable it.
Check the variable in the payload code, when coreboot SBI
is used, and print out if it is enabled.

The SiFive FU540 and FU740 do not support this register;
set the variable to n for those parts.

Add constants for this new CSR.

Change-Id: I6ea302a5acd98f6941bf314da89dd003ab20b596
Signed-off-by: Ronald G Minnich <rminnich@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81425
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>

src/arch/riscv/Kconfig

@@ -110,4 +110,13 @@ config RISCV_USE_ARCH_TIMER
 config RISCV_WORKING_HARTID
 	int
 
+# Newer SoC have the menvconfig register.
+# Very few SOC do not have this.
+# Older SoC, such as the SiFive FU[57]40, that
+# do not have this register, should set this
+# to n.
+config RISCV_SOC_HAS_MENVCFG
+	bool
+	default y
+
 endif # if ARCH_RISCV

src/arch/riscv/include/arch/encoding.h

@@ -800,6 +800,8 @@
 #define CSR_MIE 0x304
 #define CSR_MTVEC 0x305
 #define CSR_MCOUNTEREN 0x306
+#define CSR_MENVCFG 0x30a
+#define CSR_MENVCFGH 0x31a
 #define CSR_MSCRATCH 0x340
 #define CSR_MEPC 0x341
 #define CSR_MCAUSE 0x342
@@ -1292,6 +1294,8 @@ DECLARE_CSR(mideleg, CSR_MIDELEG)
 DECLARE_CSR(mie, CSR_MIE)
 DECLARE_CSR(mtvec, CSR_MTVEC)
 DECLARE_CSR(mcounteren, CSR_MCOUNTEREN)
+DECLARE_CSR(menvcfg, CSR_MENVCFG)
+DECLARE_CSR(menvcfgh, CSR_MENVCFGH)
 DECLARE_CSR(mscratch, CSR_MSCRATCH)
 DECLARE_CSR(mepc, CSR_MEPC)
 DECLARE_CSR(mcause, CSR_MCAUSE)

src/soc/sifive/fu540/Kconfig

@@ -48,4 +48,9 @@ config OPENSBI_PLATFORM
 config OPENSBI_TEXT_START
 	hex
 	default 0x80000000
+
+config RISCV_SOC_HAS_MENVCFG
+	bool
+	default n
+
 endif

src/soc/sifive/fu740/Kconfig

@@ -60,4 +60,8 @@ config OPENSBI_FW_DYNAMIC_BOOT_HART
 	  Choose the first U74 core as boot hart since
 	  hart 0 is the S7 which does not support Supervisor mode
 
+config RISCV_SOC_HAS_MENVCFG
+	bool
+	default n
+
 endif