linux-kernel - PROBLEM: module i2c_pca_isa PC9564, interrupt problem

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Message-ID: <4651BEFD.2080700@technord.com>
Date:	Mon, 21 May 2007 17:47:09 +0200
From:	alain meirhaeghe <ame@...hnord.com>
To:	linux-kernel@...r.kernel.org
Subject: PROBLEM: module i2c_pca_isa PC9564, interrupt problem

Hello,
I think there is a bug in i2c_pca_isa driver.
Problem is interrupt running on arm720 system linux-2.6.20.1.

Description of the problem:
When driver write to pc9564 an infinite loop interrupt appear (bloquing 
the system).


J think it is because the acknowledge of interrupt is not do correctly.
Acknowledge of interrupt is done outside interrupt .
J think it is dangerous if latency time of interrupt is short (as in ARM 
processor).

See existing code below:
static int pca_isa_waitforinterrupt(struct i2c_algo_pca_data *adap)
{
    int ret = 0;
    if (irq > -1)
    {
        ret = wait_event_interruptible(pca_wait,pca_isa_readbyte(adap, 
I2C_PCA_CON) & I2C_PCA_CON_SI);
      
    } else
    {
        while ((pca_isa_readbyte(adap, I2C_PCA_CON) & I2C_PCA_CON_SI) == 0)
            udelay(100);
    }
    return ret;
}

static irqreturn_t pca_handler(int this_irq, void *dev_id) {
   
    wake_up_interruptible(&pca_wait);
    return IRQ_HANDLED;
}

Isa_wait is never waked because pca_handler is always call, because j 
think it is necessary to acknowledge the interrupt in the interrupt 
handler as usual.
My temporary solution is:
static irqreturn_t pca_handler(int this_irq, void *dev_id) {
    disable_irq(irq);   // !!!!!!!!!!!!!!!!!!! temporary patch
    wake_up_interruptible(&pca_wait);
    return IRQ_HANDLED;
}



How can we correct this  ?

Thank to all
Alain Meirhaeghe




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