On Sat, May 16, 2009 at 06:28:47AM +0800, Wu Zhangjin wrote:
> read back after write, otherwise, there will be many spurious irqs from
> it
> ---
> arch/mips/kernel/i8259.c | 5 +++++
> arch/mips/loongson/common/bonito-irq.c | 4 ++++
> 2 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/arch/mips/kernel/i8259.c b/arch/mips/kernel/i8259.c
> index 413bd1d..f7c3a2b 100644
> --- a/arch/mips/kernel/i8259.c
> +++ b/arch/mips/kernel/i8259.c
> @@ -175,12 +175,17 @@ handle_real_irq:
> if (irq & 8) {
> inb(PIC_SLAVE_IMR); /* DUMMY - (do we need this?) */
> outb(cached_slave_mask, PIC_SLAVE_IMR);
> + inb(PIC_SLAVE_IMR);
> outb(0x60+(irq&7), PIC_SLAVE_CMD);/* 'Specific EOI' to slave */
> + inb(PIC_SLAVE_CMD);
> outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD); /* 'Specific EOI' to
> master-IRQ2 */
> + inb(PIC_MASTER_CMD);
> } else {
> inb(PIC_MASTER_IMR); /* DUMMY - (do we need this?) */
> outb(cached_master_mask, PIC_MASTER_IMR);
> + inb(PIC_SLAVE_IMR);
> outb(0x60+irq, PIC_MASTER_CMD); /* 'Specific EOI to master */
> + inb(PIC_MASTER_CMD);
> }
> smtc_im_ack_irq(irq);
> spin_unlock_irqrestore(&i8259A_lock, flags);
The semantic of inX() / outX() is defined by the x86 architecture which
forbids posting I/O port writes. In short I think this one is papering
over a bug in the outX() implementation.
I'm ok with the bonito part of this patch.
Ralf
