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From: Atish Patra <atishp@rivosinc.com>
To: linux-kernel@vger.kernel.org
Cc: Atish Patra <atishp@rivosinc.com>,
	Atish Patra <atishp@atishpatra.org>,
	Anup Patel <anup@brainfault.org>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	devicetree@vger.kernel.org, Jisheng Zhang <jszhang@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
	linux-riscv@lists.infradead.org,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Rob Herring <robh+dt@kernel.org>
Subject: [PATCH v3 3/4] RISC-V: Prefer sstc extension if available
Date: Tue, 26 Apr 2022 11:52:44 -0700	[thread overview]
Message-ID: <20220426185245.281182-4-atishp@rivosinc.com> (raw)
In-Reply-To: <20220426185245.281182-1-atishp@rivosinc.com>

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 <atishp@rivosinc.com>
---
 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 <asm/sbi.h>
 #include <asm/timex.h>
 
+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;
 }
 
-- 
2.25.1


WARNING: multiple messages have this Message-ID
From: Atish Patra <atishp@rivosinc.com>
To: linux-kernel@vger.kernel.org
Cc: Atish Patra <atishp@rivosinc.com>,
	Atish Patra <atishp@atishpatra.org>,
	Anup Patel <anup@brainfault.org>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	devicetree@vger.kernel.org, Jisheng Zhang <jszhang@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
	linux-riscv@lists.infradead.org,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Rob Herring <robh+dt@kernel.org>
Subject: [PATCH v3 3/4] RISC-V: Prefer sstc extension if available
Date: Tue, 26 Apr 2022 11:52:44 -0700	[thread overview]
Message-ID: <20220426185245.281182-4-atishp@rivosinc.com> (raw)
In-Reply-To: <20220426185245.281182-1-atishp@rivosinc.com>

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 <atishp@rivosinc.com>
---
 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 <asm/sbi.h>
 #include <asm/timex.h>
 
+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;
 }
 
-- 
2.25.1


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  parent reply	other threads:[~2022-04-26 18:53 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-26 18:52 [PATCH v3 0/4] Add Sstc extension support Atish Patra
2022-04-26 18:52 ` Atish Patra
2022-04-26 18:52 ` [PATCH v3 1/4] RISC-V: Add SSTC extension CSR details Atish Patra
2022-04-26 18:52   ` Atish Patra
2022-05-24 11:24   ` Anup Patel
2022-05-24 11:24     ` Anup Patel
2022-04-26 18:52 ` [PATCH v3 2/4] RISC-V: Enable sstc extension parsing from DT Atish Patra
2022-04-26 18:52   ` Atish Patra
2022-05-24 11:25   ` Anup Patel
2022-05-24 11:25     ` Anup Patel
2022-04-26 18:52 ` Atish Patra [this message]
2022-04-26 18:52   ` [PATCH v3 3/4] RISC-V: Prefer sstc extension if available Atish Patra
2022-05-24 11:30   ` Anup Patel
2022-05-24 11:30     ` Anup Patel
2022-04-26 18:52 ` [PATCH v3 4/4] RISC-V: KVM: Support sstc extension Atish Patra
2022-04-26 18:52   ` Atish Patra
2022-04-26 21:10   ` Jessica Clarke
2022-04-26 21:10     ` Jessica Clarke
2022-05-08  7:49     ` Atish Patra
2022-05-08  7:49       ` Atish Patra
2022-05-24 11:39   ` Anup Patel
2022-05-24 11:39     ` Anup Patel

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