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[70.228.75.190]) by smtp.gmail.com with ESMTPSA id 20-20020ac84e94000000b002de8f564305sm4605481qtp.1.2022.03.04.12.10.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Mar 2022 12:10:43 -0800 (PST) From: Atish Patra To: linux-kernel@vger.kernel.org Cc: Atish Patra , Atish Patra , Anup Patel , Damien Le Moal , devicetree@vger.kernel.org, Jisheng Zhang , Krzysztof Kozlowski , kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, Palmer Dabbelt , Paul Walmsley , Rob Herring Subject: [RFC PATCH v2 3/7] RISC-V: Prefer sstc extension if available Date: Fri, 4 Mar 2022 12:10:16 -0800 Message-Id: <20220304201020.810380-4-atishp@rivosinc.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220304201020.810380-1-atishp@rivosinc.com> References: <20220304201020.810380-1-atishp@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Atish Patra --- drivers/clocksource/timer-riscv.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c index 1767f8bf2013..d9398ae84a20 100644 --- a/drivers/clocksource/timer-riscv.c +++ b/drivers/clocksource/timer-riscv.c @@ -23,11 +23,24 @@ #include #include +static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available); + static int riscv_clock_next_event(unsigned long delta, struct clock_event_device *ce) { + uint64_t 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 __riscv_xlen == 32 + 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 +178,12 @@ 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; } -- 2.30.2