[PATCH v8 15/21] riscv: Add option to support RISC-V privileged spec 1.9

[Sean Anderson]

Some older processors (notably the Kendryte K210) use an older version of
the RISC-V privileged specification. The primary changes between the old
and new are in virtual memory, and in the merging of three separate counter
enable CSRs.  Using the new CSR on an old processor causes an illegal
instruction exception.  This patch adds an option to use the old CSRs
instead of the new one.

Signed-off-by: Sean Anderson <seanga2 at gmail.com>
Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
---

Changes in v6:
- Reformat so chechpatch errors less

Changes in v5:
- Rename to 1.9 to reflect the spec as implemented by the k210

Changes in v4:
- Fixed CSRs not being defined properly (thanks bmeng)
- Added ifdefs for all changed CSRs (e.g. for VM)
- Also properly disable VM on boot

Changes in v3:
- Renamed from "riscv: Add option to disable writes to mcounteren"
- Added original functionality back for older priv specs.

Changes in v2:
- Moved forward in the patch series

 arch/riscv/Kconfig           | 10 +++++++++
 arch/riscv/cpu/cpu.c         |  9 ++++++++
 arch/riscv/include/asm/csr.h | 40 ++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index cc87da7e04..a42cb58b56 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -238,6 +238,16 @@ config XIP
 config SHOW_REGS
 	bool "Show registers on unhandled exception"
 
+config RISCV_PRIV_1_9
+	bool "Use version 1.9 of the RISC-V priviledged specification"
+	help
+	  Older versions of the RISC-V priviledged specification had
+	  separate counter enable CSRs for each privilege mode. Writing
+	  to the unified mcounteren CSR on a processor implementing the
+	  old specification will result in an illegal instruction
+	  exception. In addition to counter CSR changes, the way virtual
+	  memory is configured was also changed.
+
 config STACK_SIZE_SHIFT
 	int
 	default 14
diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
index f851374255..3c1836694a 100644
--- a/arch/riscv/cpu/cpu.c
+++ b/arch/riscv/cpu/cpu.c
@@ -89,11 +89,20 @@ int arch_cpu_init_dm(void)
 		 * Enable perf counters for cycle, time,
 		 * and instret counters only
 		 */
+#ifdef CONFIG_RISCV_PRIV_1_9
+		csr_write(CSR_MSCOUNTEREN, GENMASK(2, 0));
+		csr_write(CSR_MUCOUNTEREN, GENMASK(2, 0));
+#else
 		csr_write(CSR_MCOUNTEREN, GENMASK(2, 0));
+#endif
 
 		/* Disable paging */
 		if (supports_extension('s'))
+#ifdef CONFIG_RISCV_PRIV_1_9
+			csr_read_clear(CSR_MSTATUS, SR_VM);
+#else
 			csr_write(CSR_SATP, 0);
+#endif
 	}
 
 #ifdef CONFIG_SMP
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index d1520743a2..1a15089cae 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -15,7 +15,11 @@
 #define SR_SIE		_AC(0x00000002, UL) /* Supervisor Interrupt Enable */
 #define SR_SPIE		_AC(0x00000020, UL) /* Previous Supervisor IE */
 #define SR_SPP		_AC(0x00000100, UL) /* Previously Supervisor */
+#ifdef CONFIG_RISCV_PRIV_1_9
+#define SR_PUM		_AC(0x00040000, UL) /* Protect User Memory Access */
+#else
 #define SR_SUM		_AC(0x00040000, UL) /* Supervisor User Memory Access */
+#endif
 
 #define SR_FS		_AC(0x00006000, UL) /* Floating-point Status */
 #define SR_FS_OFF	_AC(0x00000000, UL)
@@ -29,6 +33,22 @@
 #define SR_XS_CLEAN	_AC(0x00010000, UL)
 #define SR_XS_DIRTY	_AC(0x00018000, UL)
 
+#ifdef CONFIG_RISCV_PRIV_1_9
+#define SR_VM		_AC(0x1F000000, UL) /* Virtualization Management */
+#define SR_VM_MODE_BARE	_AC(0x00000000, UL) /* No translation or protection */
+#define SR_VM_MODE_BB	_AC(0x01000000, UL) /* Single base-and-bound */
+/* Separate instruction and data base-and-bound */
+#define SR_VM_MODE_BBID	_AC(0x02000000, UL)
+#ifndef CONFIG_64BIT
+#define SR_VM_MODE_32	_AC(0x08000000, UL)
+#define SR_VM_MODE	SR_VM_MODE_32
+#else
+#define SR_VM_MODE_39	_AC(0x09000000, UL)
+#define SR_VM_MODE_48	_AC(0x0A000000, UL)
+#define SR_VM_MODE	SR_VM_MODE_39
+#endif
+#endif
+
 #ifndef CONFIG_64BIT
 #define SR_SD		_AC(0x80000000, UL) /* FS/XS dirty */
 #else
@@ -36,6 +56,7 @@
 #endif
 
 /* SATP flags */
+#ifndef CONFIG_RISCV_PRIV_1_9
 #ifndef CONFIG_64BIT
 #define SATP_PPN	_AC(0x003FFFFF, UL)
 #define SATP_MODE_32	_AC(0x80000000, UL)
@@ -45,6 +66,7 @@
 #define SATP_MODE_39	_AC(0x8000000000000000, UL)
 #define SATP_MODE	SATP_MODE_39
 #endif
+#endif
 
 /* SCAUSE */
 #define SCAUSE_IRQ_FLAG		(_AC(1, UL) << (__riscv_xlen - 1))
@@ -88,17 +110,35 @@
 #define CSR_SCAUSE		0x142
 #define CSR_STVAL		0x143
 #define CSR_SIP			0x144
+#ifdef CONFIG_RISCV_PRIV_1_9
+#define CSR_SPTBR		0x180
+#else
 #define CSR_SATP		0x180
+#endif
 #define CSR_MSTATUS		0x300
 #define CSR_MISA		0x301
 #define CSR_MIE			0x304
 #define CSR_MTVEC		0x305
+#ifdef CONFIG_RISCV_PRIV_1_9
+#define CSR_MUCOUNTEREN         0x320
+#define CSR_MSCOUNTEREN         0x321
+#define CSR_MHCOUNTEREN         0x322
+#else
 #define CSR_MCOUNTEREN		0x306
+#endif
 #define CSR_MSCRATCH		0x340
 #define CSR_MEPC		0x341
 #define CSR_MCAUSE		0x342
 #define CSR_MTVAL		0x343
 #define CSR_MIP			0x344
+#ifdef CONFIG_RISCV_PRIV_1_9
+#define CSR_MBASE		0x380
+#define CSR_MBOUND		0x381
+#define CSR_MIBASE		0x382
+#define CSR_MIBOUND		0x383
+#define CSR_MDBASE		0x384
+#define CSR_MDBOUND		0x385
+#endif
 #define CSR_CYCLEH		0xc80
 #define CSR_TIMEH		0xc81
 #define CSR_INSTRETH		0xc82
-- 
2.25.1