linux-kernel - [PATCH 2/2] RISC-V: Move to the new asm-generic IRQ handler

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Message-Id: <20180118154005.24994-3-palmer@sifive.com>
Date:   Thu, 18 Jan 2018 07:40:05 -0800
From:   Palmer Dabbelt <palmer@...ive.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Christoph Hellwig <hch@...radead.org>,
        linux-kernel@...r.kernel.org
Cc:     patches@...ups.riscv.org, Palmer Dabbelt <palmer@...ive.com>
Subject: [PATCH 2/2] RISC-V: Move to the new asm-generic IRQ handler

The old mechanism for handling IRQs on RISC-V was pretty ugly: the arch
code looked at the Kconfig entry for our first-level irqchip driver and
called into it directly.

This patch uses the new asm-generic IRQ handling infastructure, which
essentially just deletes a bunch of code.  This does add an additional
load to the interrupt latency, but there's a lot of tuning left to be
done there on RISC-V so I think it's OK for now.

Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
---
 arch/riscv/Kconfig            |  1 +
 arch/riscv/include/asm/Kbuild |  1 +
 arch/riscv/kernel/entry.S     |  5 +++--
 arch/riscv/kernel/irq.c       | 13 -------------
 4 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2c6adf12713a..49faed9e8b93 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -35,6 +35,7 @@ config RISCV
 	select THREAD_INFO_IN_TASK
 	select RISCV_IRQ_INTC
 	select RISCV_TIMER
+	select GENERIC_HANDLE_IRQ
 
 config MMU
 	def_bool y
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 970460a0b492..e0d0fbe43ca2 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -16,6 +16,7 @@ generic-y += ftrace.h
 generic-y += futex.h
 generic-y += hardirq.h
 generic-y += hash.h
+generic-y += handle_irq.h
 generic-y += hw_irq.h
 generic-y += ioctl.h
 generic-y += ioctls.h
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 7404ec222406..a79869151aea 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -166,8 +166,9 @@ ENTRY(handle_exception)
 	/* Handle interrupts */
 	slli a0, s4, 1
 	srli a0, a0, 1
-	move a1, sp /* pt_regs */
-	tail do_IRQ
+	move a0, sp /* pt_regs */
+	REG_L a1, handle_arch_irq
+	jr a1
 1:
 	/* Handle syscalls */
 	li t0, EXC_SYSCALL
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 328718e8026e..b74cbfbce2d0 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -24,16 +24,3 @@ void __init init_IRQ(void)
 {
 	irqchip_init();
 }
-
-asmlinkage void __irq_entry do_IRQ(unsigned int cause, struct pt_regs *regs)
-{
-#ifdef CONFIG_RISCV_INTC
-	/*
-	 * FIXME: We don't want a direct call to riscv_intc_irq here.  The plan
-	 * is to put an IRQ domain here and let the interrupt controller
-	 * register with that, but I poked around the arm64 code a bit and
-	 * there might be a better way to do it (ie, something fully generic).
-	 */
-	riscv_intc_irq(cause, regs);
-#endif
-}
-- 
2.13.6