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Subject[PATCH v6 3/3] RISC-V: Access CSRs using CSR numbers
Date
We should prefer accessing CSRs using their CSR numbers because:
1. It compiles fine with older toolchains.
2. We can use latest CSR names in #define macro names of CSR numbers
as-per RISC-V spec.
3. We can access newly added CSRs even if toolchain does not recognize
newly addes CSRs by name.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
arch/riscv/include/asm/csr.h | 32 ++++++++++++++++++++++------
arch/riscv/include/asm/irqflags.h | 10 ++++-----
arch/riscv/include/asm/mmu_context.h | 7 +-----
arch/riscv/kernel/entry.S | 22 +++++++++----------
arch/riscv/kernel/head.S | 12 +++++------
arch/riscv/kernel/perf_event.c | 4 ++--
arch/riscv/kernel/smp.c | 2 +-
arch/riscv/kernel/traps.c | 6 +++---
arch/riscv/mm/fault.c | 6 +-----
9 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index a89a9bf2c7f2..3c3c26c3a1f1 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -14,6 +14,7 @@
#ifndef _ASM_RISCV_CSR_H
#define _ASM_RISCV_CSR_H

+#include <asm/asm.h>
#include <linux/const.h>

/* Status register flags */
@@ -79,12 +80,29 @@
#define SIE_STIE (_AC(0x1, UL) << IRQ_S_TIMER)
#define SIE_SEIE (_AC(0x1, UL) << IRQ_S_EXT)

+#define CSR_CYCLE 0xc00
+#define CSR_TIME 0xc01
+#define CSR_INSTRET 0xc02
+#define CSR_SSTATUS 0x100
+#define CSR_SIE 0x104
+#define CSR_STVEC 0x105
+#define CSR_SCOUNTEREN 0x106
+#define CSR_SSCRATCH 0x140
+#define CSR_SEPC 0x141
+#define CSR_SCAUSE 0x142
+#define CSR_STVAL 0x143
+#define CSR_SIP 0x144
+#define CSR_SATP 0x180
+#define CSR_CYCLEH 0xc80
+#define CSR_TIMEH 0xc81
+#define CSR_INSTRETH 0xc82
+
#ifndef __ASSEMBLY__

#define csr_swap(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
- __asm__ __volatile__ ("csrrw %0, " #csr ", %1" \
+ __asm__ __volatile__ ("csrrw %0, " __ASM_STR(csr) ", %1"\
: "=r" (__v) : "rK" (__v) \
: "memory"); \
__v; \
@@ -93,7 +111,7 @@
#define csr_read(csr) \
({ \
register unsigned long __v; \
- __asm__ __volatile__ ("csrr %0, " #csr \
+ __asm__ __volatile__ ("csrr %0, " __ASM_STR(csr) \
: "=r" (__v) : \
: "memory"); \
__v; \
@@ -102,7 +120,7 @@
#define csr_write(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
- __asm__ __volatile__ ("csrw " #csr ", %0" \
+ __asm__ __volatile__ ("csrw " __ASM_STR(csr) ", %0" \
: : "rK" (__v) \
: "memory"); \
})
@@ -110,7 +128,7 @@
#define csr_read_set(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
- __asm__ __volatile__ ("csrrs %0, " #csr ", %1" \
+ __asm__ __volatile__ ("csrrs %0, " __ASM_STR(csr) ", %1"\
: "=r" (__v) : "rK" (__v) \
: "memory"); \
__v; \
@@ -119,7 +137,7 @@
#define csr_set(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
- __asm__ __volatile__ ("csrs " #csr ", %0" \
+ __asm__ __volatile__ ("csrs " __ASM_STR(csr) ", %0" \
: : "rK" (__v) \
: "memory"); \
})
@@ -127,7 +145,7 @@
#define csr_read_clear(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
- __asm__ __volatile__ ("csrrc %0, " #csr ", %1" \
+ __asm__ __volatile__ ("csrrc %0, " __ASM_STR(csr) ", %1"\
: "=r" (__v) : "rK" (__v) \
: "memory"); \
__v; \
@@ -136,7 +154,7 @@
#define csr_clear(csr, val) \
({ \
unsigned long __v = (unsigned long)(val); \
- __asm__ __volatile__ ("csrc " #csr ", %0" \
+ __asm__ __volatile__ ("csrc " __ASM_STR(csr) ", %0" \
: : "rK" (__v) \
: "memory"); \
})
diff --git a/arch/riscv/include/asm/irqflags.h b/arch/riscv/include/asm/irqflags.h
index 07a3c6d5706f..1a69b3bcd371 100644
--- a/arch/riscv/include/asm/irqflags.h
+++ b/arch/riscv/include/asm/irqflags.h
@@ -21,25 +21,25 @@
/* read interrupt enabled status */
static inline unsigned long arch_local_save_flags(void)
{
- return csr_read(sstatus);
+ return csr_read(CSR_SSTATUS);
}

/* unconditionally enable interrupts */
static inline void arch_local_irq_enable(void)
{
- csr_set(sstatus, SR_SIE);
+ csr_set(CSR_SSTATUS, SR_SIE);
}

/* unconditionally disable interrupts */
static inline void arch_local_irq_disable(void)
{
- csr_clear(sstatus, SR_SIE);
+ csr_clear(CSR_SSTATUS, SR_SIE);
}

/* get status and disable interrupts */
static inline unsigned long arch_local_irq_save(void)
{
- return csr_read_clear(sstatus, SR_SIE);
+ return csr_read_clear(CSR_SSTATUS, SR_SIE);
}

/* test flags */
@@ -57,7 +57,7 @@ static inline int arch_irqs_disabled(void)
/* set interrupt enabled status */
static inline void arch_local_irq_restore(unsigned long flags)
{
- csr_set(sstatus, flags & SR_SIE);
+ csr_set(CSR_SSTATUS, flags & SR_SIE);
}

#endif /* _ASM_RISCV_IRQFLAGS_H */
diff --git a/arch/riscv/include/asm/mmu_context.h b/arch/riscv/include/asm/mmu_context.h
index 336d60ec5698..98c76c821367 100644
--- a/arch/riscv/include/asm/mmu_context.h
+++ b/arch/riscv/include/asm/mmu_context.h
@@ -83,12 +83,7 @@ static inline void switch_mm(struct mm_struct *prev,
cpumask_clear_cpu(cpu, mm_cpumask(prev));
cpumask_set_cpu(cpu, mm_cpumask(next));

- /*
- * Use the old spbtr name instead of using the current satp
- * name to support binutils 2.29 which doesn't know about the
- * privileged ISA 1.10 yet.
- */
- csr_write(sptbr, virt_to_pfn(next->pgd) | SATP_MODE);
+ csr_write(CSR_SATP, virt_to_pfn(next->pgd) | SATP_MODE);
local_flush_tlb_all();

flush_icache_deferred(next);
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index fd9b57c8b4ce..1c1ecc238cfa 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -37,11 +37,11 @@
* the kernel thread pointer. If we came from the kernel, sscratch
* will contain 0, and we should continue on the current TP.
*/
- csrrw tp, sscratch, tp
+ csrrw tp, CSR_SSCRATCH, tp
bnez tp, _save_context

_restore_kernel_tpsp:
- csrr tp, sscratch
+ csrr tp, CSR_SSCRATCH
REG_S sp, TASK_TI_KERNEL_SP(tp)
_save_context:
REG_S sp, TASK_TI_USER_SP(tp)
@@ -87,11 +87,11 @@ _save_context:
li t0, SR_SUM | SR_FS

REG_L s0, TASK_TI_USER_SP(tp)
- csrrc s1, sstatus, t0
- csrr s2, sepc
- csrr s3, sbadaddr
- csrr s4, scause
- csrr s5, sscratch
+ csrrc s1, CSR_SSTATUS, t0
+ csrr s2, CSR_SEPC
+ csrr s3, CSR_STVAL
+ csrr s4, CSR_SCAUSE
+ csrr s5, CSR_SSCRATCH
REG_S s0, PT_SP(sp)
REG_S s1, PT_SSTATUS(sp)
REG_S s2, PT_SEPC(sp)
@@ -107,8 +107,8 @@ _save_context:
.macro RESTORE_ALL
REG_L a0, PT_SSTATUS(sp)
REG_L a2, PT_SEPC(sp)
- csrw sstatus, a0
- csrw sepc, a2
+ csrw CSR_SSTATUS, a0
+ csrw CSR_SEPC, a2

REG_L x1, PT_RA(sp)
REG_L x3, PT_GP(sp)
@@ -155,7 +155,7 @@ ENTRY(handle_exception)
* Set sscratch register to 0, so that if a recursive exception
* occurs, the exception vector knows it came from the kernel
*/
- csrw sscratch, x0
+ csrw CSR_SSCRATCH, x0

/* Load the global pointer */
.option push
@@ -248,7 +248,7 @@ resume_userspace:
* Save TP into sscratch, so we can find the kernel data structures
* again.
*/
- csrw sscratch, tp
+ csrw CSR_SSCRATCH, tp

restore_all:
RESTORE_ALL
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index fe884cd69abd..041492636b45 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -23,7 +23,7 @@
__INIT
ENTRY(_start)
/* Mask all interrupts */
- csrw sie, zero
+ csrw CSR_SIE, zero

/* Load the global pointer */
.option push
@@ -89,7 +89,7 @@ relocate:
/* Point stvec to virtual address of intruction after satp write */
la a0, 1f
add a0, a0, a1
- csrw stvec, a0
+ csrw CSR_STVEC, a0

/* Compute satp for kernel page tables, but don't load it yet */
la a2, swapper_pg_dir
@@ -105,12 +105,12 @@ relocate:
srl a0, a0, PAGE_SHIFT
or a0, a0, a1
sfence.vma
- csrw sptbr, a0
+ csrw CSR_SATP, a0
.align 2
1:
/* Set trap vector to spin forever to help debug */
la a0, .Lsecondary_park
- csrw stvec, a0
+ csrw CSR_STVEC, a0

/* Reload the global pointer */
.option push
@@ -119,7 +119,7 @@ relocate:
.option pop

/* Switch to kernel page tables */
- csrw sptbr, a2
+ csrw CSR_SATP, a2

ret

@@ -130,7 +130,7 @@ relocate:

/* Set trap vector to spin forever to help debug */
la a3, .Lsecondary_park
- csrw stvec, a3
+ csrw CSR_STVEC, a3

slli a3, a0, LGREG
la a1, __cpu_up_stack_pointer
diff --git a/arch/riscv/kernel/perf_event.c b/arch/riscv/kernel/perf_event.c
index 667ee70defea..91626d9ae5f2 100644
--- a/arch/riscv/kernel/perf_event.c
+++ b/arch/riscv/kernel/perf_event.c
@@ -185,10 +185,10 @@ static inline u64 read_counter(int idx)

switch (idx) {
case RISCV_PMU_CYCLE:
- val = csr_read(cycle);
+ val = csr_read(CSR_CYCLE);
break;
case RISCV_PMU_INSTRET:
- val = csr_read(instret);
+ val = csr_read(CSR_INSTRET);
break;
default:
WARN_ON_ONCE(idx < 0 || idx > RISCV_MAX_COUNTERS);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 0c41d07ec281..f244c63d29e4 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -89,7 +89,7 @@ void riscv_software_interrupt(void)
unsigned long *stats = ipi_data[smp_processor_id()].stats;

/* Clear pending IPI */
- csr_clear(sip, SIE_SSIE);
+ csr_clear(CSR_SIP, SIE_SSIE);

while (true) {
unsigned long ops;
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 24a9333dda2c..1b407a9db3fc 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -159,9 +159,9 @@ void __init trap_init(void)
* Set sup0 scratch register to 0, indicating to exception vector
* that we are presently executing in the kernel
*/
- csr_write(sscratch, 0);
+ csr_write(CSR_SSCRATCH, 0);
/* Set the exception vector address */
- csr_write(stvec, &handle_exception);
+ csr_write(CSR_STVEC, &handle_exception);
/* Enable all interrupts */
- csr_write(sie, -1);
+ csr_write(CSR_SIE, -1);
}
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 88401d5125bc..26293bc053a8 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -239,13 +239,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
* Do _not_ use "tsk->active_mm->pgd" here.
* We might be inside an interrupt in the middle
* of a task switch.
- *
- * Note: Use the old spbtr name instead of using the current
- * satp name to support binutils 2.29 which doesn't know about
- * the privileged ISA 1.10 yet.
*/
index = pgd_index(addr);
- pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr)) + index;
+ pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index;
pgd_k = init_mm.pgd + index;

if (!pgd_present(*pgd_k))
--
2.17.1
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