Re: [patches] Re: [PATCH v2 4/4] RISC-V: Move to the new generic IRQ handler

Palmer Dabbelt
2018-01-25T16:04:41Z

On Thu, 25 Jan 2018 00:31:53 PST (-0800), shorne@gmail.com wrote:
> On Wed, Jan 24, 2018 at 07:07:56PM -0800, Palmer Dabbelt wrote:
>> 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 0generic 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@sifive.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..e67f42178059 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 MULTI_IRQ_HANDLER
>>
>> 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
>
> Hi Palmer,
>
> Do we need these shifts into a0? I guess these were used when this was an arg
> to do_IRQ, but no longer needed since you put pt_regs into a0 in the next
> instruction.

Thanks!

> Other than that it looks good, and thanks for looking at OpenRISC too.
>
> Acked-by: Stafford Horne <shorne@gmail.com>
>
>
>> - 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
>>