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Re: [Qemu-ppc] [Qemu-devel] Disabling IRQ error

From: Xie Xianshan
Subject: Re: [Qemu-ppc] [Qemu-devel] Disabling IRQ error
Date: Thu, 12 Sep 2013 15:49:59 +0800
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv: Gecko/20120306 Thunderbird/3.1.20

Hi Max,
    Thanks for your patience and help.
    I`ve tried to do what you said, but the problem doesn`t go away.
And actually i cannot add a new register to the fpga device, because the fpga device i`m emulating already exists in the real world. So i cannot change anything about hardware properties and linux driver for this device.

    By the way, how did you finally fix your problem?


于 2013/09/11 17:29, Max Filippov 写道:
On Wed, Sep 11, 2013 at 12:12 PM, Xie Xianshan<address@hidden>  wrote:
   I want to add a new device "fpga" for e500, and trigger an interrupt IRQ3
while the register BB_INTR_REG which belongs to device "fpga" is wrote by
the device driver of "fpga".
   For e500, IRQ3 is an external interrupt irq.
   According the debug log, the disabling error is encoutered during writing
BB_INTR_REG register.
   - write BB_INTR_REG register
       - qemu_irq_raise() is called.
       - after serval minutes,
         the error message about disabling irq is displayed.
   - continue the next execution without error(with poll?)

So your device raises IRQ, but it doesn't lower it. Real devices
usually don't do that, they either generate a short pulse on the
IRQ line (in case of edge-triggered IRQ) or raise IRQ line on
some event and then lower it on a command from its driver
(level-triggered IRQ).

You can do the following to make your device behave that way:
- make your fpga device capable of lowering its IRQ, e.g. by adding
   another register:

static void fpga_write(FPGAState *s, unsigned int offset, uint32_t value,
unsigned size) {
     switch(offset) {
     case BB_INTR_REG:
        case BB_INTC_REG:

- provide an interrupt service routine in the linux driver for your fpga
   device that would check whether the interrupt was caused by its
   device, and if so lower the device's IRQ.

-- Max

Best Regards
Xie Xianshan
Xie Xianshan
Development Dept.I
Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST)
No. 6 Wenzhu Road, Nanjing, 210012, China
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