From bf952a290f7a9d818204b9b68e861655f8b15a65 Mon Sep 17 00:00:00 2001 From: Atish Patra Date: Fri, 22 Jul 2022 09:50:44 -0700 Subject: [PATCH 1/3] RISC-V: Add SSTC extension CSR details This patch just introduces the required CSR fields related to the SSTC extension. Reviewed-by: Anup Patel Signed-off-by: Atish Patra Link: https://lore.kernel.org/r/20220722165047.519994-2-atishp@rivosinc.com Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/csr.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h index 6d85655e7edf..34f4eaf326c4 100644 --- a/arch/riscv/include/asm/csr.h +++ b/arch/riscv/include/asm/csr.h @@ -235,6 +235,9 @@ #define CSR_SIP 0x144 #define CSR_SATP 0x180 +#define CSR_STIMECMP 0x14D +#define CSR_STIMECMPH 0x15D + #define CSR_VSSTATUS 0x200 #define CSR_VSIE 0x204 #define CSR_VSTVEC 0x205 @@ -244,6 +247,8 @@ #define CSR_VSTVAL 0x243 #define CSR_VSIP 0x244 #define CSR_VSATP 0x280 +#define CSR_VSTIMECMP 0x24D +#define CSR_VSTIMECMPH 0x25D #define CSR_HSTATUS 0x600 #define CSR_HEDELEG 0x602 From 464b0187ff94fcc629fe7cd350e16a3b9e80ed9e Mon Sep 17 00:00:00 2001 From: Atish Patra Date: Fri, 22 Jul 2022 09:50:45 -0700 Subject: [PATCH 2/3] RISC-V: Enable sstc extension parsing from DT The ISA extension framework now allows parsing any multi-letter ISA extension. Enable that for sstc extension. Reviewed-by: Anup Patel Signed-off-by: Atish Patra Link: https://lore.kernel.org/r/20220722165047.519994-3-atishp@rivosinc.com Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/hwcap.h | 1 + arch/riscv/kernel/cpu.c | 1 + arch/riscv/kernel/cpufeature.c | 1 + 3 files changed, 3 insertions(+) diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h index 4e2486881840..b186fff75198 100644 --- a/arch/riscv/include/asm/hwcap.h +++ b/arch/riscv/include/asm/hwcap.h @@ -53,6 +53,7 @@ extern unsigned long elf_hwcap; enum riscv_isa_ext_id { RISCV_ISA_EXT_SSCOFPMF = RISCV_ISA_EXT_BASE, RISCV_ISA_EXT_SVPBMT, + RISCV_ISA_EXT_SSTC, RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX, }; diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c index fba9e9f46a8c..0016d9337fe0 100644 --- a/arch/riscv/kernel/cpu.c +++ b/arch/riscv/kernel/cpu.c @@ -89,6 +89,7 @@ int riscv_of_parent_hartid(struct device_node *node) static struct riscv_isa_ext_data isa_ext_arr[] = { __RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF), __RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT), + __RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC), __RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX), }; diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index a6f62a6d1edd..d1d83cd9fd4b 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -199,6 +199,7 @@ void __init riscv_fill_hwcap(void) } else { SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF); SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT); + SET_ISA_EXT_MAP("sstc", RISCV_ISA_EXT_SSTC); } #undef SET_ISA_EXT_MAP } From 9f7a8ff6391fd5363363b8e5c8b1462a07922368 Mon Sep 17 00:00:00 2001 From: Atish Patra Date: Fri, 22 Jul 2022 09:50:46 -0700 Subject: [PATCH 3/3] RISC-V: Prefer sstc extension if available RISC-V ISA has sstc extension which allows updating the next clock event via a CSR (stimecmp) instead of an SBI call. This should happen dynamically if sstc extension is available. Otherwise, it will fallback to SBI call to maintain backward compatibility. Reviewed-by: Anup Patel Signed-off-by: Atish Patra Reviewed-by: Guo Ren Link: https://lore.kernel.org/r/20220722165047.519994-4-atishp@rivosinc.com Signed-off-by: Palmer Dabbelt --- drivers/clocksource/timer-riscv.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c index 593d5a957b69..05f6cf067289 100644 --- a/drivers/clocksource/timer-riscv.c +++ b/drivers/clocksource/timer-riscv.c @@ -7,6 +7,9 @@ * either be read from the "time" and "timeh" CSRs, and can use the SBI to * setup events, or directly accessed using MMIO registers. */ + +#define pr_fmt(fmt) "riscv-timer: " fmt + #include #include #include @@ -20,14 +23,28 @@ #include #include #include +#include #include #include +static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available); + static int riscv_clock_next_event(unsigned long delta, struct clock_event_device *ce) { + u64 next_tval = get_cycles64() + delta; + csr_set(CSR_IE, IE_TIE); - sbi_set_timer(get_cycles64() + delta); + if (static_branch_likely(&riscv_sstc_available)) { +#if defined(CONFIG_32BIT) + csr_write(CSR_STIMECMP, next_tval & 0xFFFFFFFF); + csr_write(CSR_STIMECMPH, next_tval >> 32); +#else + csr_write(CSR_STIMECMP, next_tval); +#endif + } else + sbi_set_timer(next_tval); + return 0; } @@ -165,6 +182,12 @@ static int __init riscv_timer_init_dt(struct device_node *n) if (error) pr_err("cpu hp setup state failed for RISCV timer [%d]\n", error); + + if (riscv_isa_extension_available(NULL, SSTC)) { + pr_info("Timer interrupt in S-mode is available via sstc extension\n"); + static_branch_enable(&riscv_sstc_available); + } + return error; }