linux-kernel - [RFC PATCH v1 3/3] RISC-V: Add handle_IPI

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Date:   Thu, 11 Mar 2021 22:17:12 +0530
From:   Anup Patel <anup.patel@....com>
To:     Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anup Patel <anup.patel@....com>
Subject: [RFC PATCH v1 3/3] RISC-V: Add handle_IPI_noregs() for irqchip drivers

We will be having IPI handled through nested interrupt controllers
(such as AIA IMSIC). The irqchip driver of such nested interrupt
controller will not do irq_enter() and save pt_regs because this
would have been already done by the irqchip driver of the parent
interrupt controller.

This patch adds handle_IPI_noregs() for nested irqchip drivers.

Signed-off-by: Anup Patel <anup.patel@....com>
---
 arch/riscv/include/asm/smp.h |  6 ++++++
 arch/riscv/kernel/smp.c      | 20 ++++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 82c23e5f22f6..b31d3ec2f71b 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -33,6 +33,12 @@ void show_ipi_stats(struct seq_file *p, int prec);
 /* SMP initialization hook for setup_arch */
 void __init setup_smp(void);
 
+/*
+ * Called from C code, this handles an IPI assuming irq_enter() and
+ * pt_regs already saved by caller.
+ */
+void handle_IPI_noregs(void);
+
 /* Called from C code, this handles an IPI. */
 void handle_IPI(struct pt_regs *regs);
 
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 9258e3eaa8c6..19e102e2d5e6 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -144,14 +144,11 @@ void arch_irq_work_raise(void)
 }
 #endif
 
-void handle_IPI(struct pt_regs *regs)
+void handle_IPI_noregs(void)
 {
-	struct pt_regs *old_regs = set_irq_regs(regs);
 	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
 	unsigned long *stats = ipi_data[smp_processor_id()].stats;
 
-	irq_enter();
-
 	riscv_clear_ipi();
 
 	while (true) {
@@ -162,7 +159,7 @@ void handle_IPI(struct pt_regs *regs)
 
 		ops = xchg(pending_ipis, 0);
 		if (ops == 0)
-			goto done;
+			break;
 
 		if (ops & (1 << IPI_RESCHEDULE)) {
 			stats[IPI_RESCHEDULE]++;
@@ -189,9 +186,20 @@ void handle_IPI(struct pt_regs *regs)
 		/* Order data access and bit testing. */
 		mb();
 	}
+}
+
+void handle_IPI(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+
+	irq_enter();
+
+	handle_IPI_noregs();
+
+	riscv_clear_ipi();
 
-done:
 	irq_exit();
+
 	set_irq_regs(old_regs);
 }
 
-- 
2.25.1