linux-kernel - About omap2 mmc host close too long irq in irqaction.

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Date:	Thu, 18 Jul 2013 10:53:01 +0800
From:	majianpeng <majianpeng@...il.com>
To:	balajitk <balajitk@...com>
Cc:	cjb <cjb@...top.org>, linux-mmc <linux-mmc@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	devicetree-discuss <devicetree-discuss@...ts.ozlabs.org>
Subject: About omap2 mmc host  close too long irq in irqaction.

Hi all,
	Now i worked on omp2 and met a probelm which someplace close_irq for 3.6second. 
The kernel version is 2.6.37. I used trace to find in irq_action:omap_hsmmc_irq.
This problem occured by removed the sdcard when there are io operations.

I found the read problem is in omap_hsmmc_reset_controller_fsm.
In omap_hsmmc_reset_controller_fsm:
>static inline void omap_hsmmc_reset_controller_fsm(struct omap_hsmmc_host *host,
>                                                   unsigned long bit)
>{
>        unsigned long i = 0; 
>        unsigned long limit = (loops_per_jiffy *
>                                msecs_to_jiffies(MMC_TIMEOUT_MS));

>        OMAP_HSMMC_WRITE(host->base, SYSCTL,
>                         OMAP_HSMMC_READ(host->base, SYSCTL) | bit);

>        /*   
>         * OMAP4 ES2 and greater has an updated reset logic.
>         * Monitor a 0->1 transition first
>         */
>        if (mmc_slot(host).features & HSMMC_HAS_UPDATED_RESET) {
>                while ((!(OMAP_HSMMC_READ(host->base, SYSCTL) & bit))
>                                       && (i++ < limit))
>                        cpu_relax();
        }    
 In func, it used loops_per_jiffy  in order to avoid do many time exceed MMC_TIMEOUT_MS.
In face oops_per_jiify is like:
while(i++ < loops_per_jiffy)
	cpu_relax();
But actually, it used as follow:
>while ((!(OMAP_HSMMC_READ(host->base, SYSCTL) & bit))
>                                      && (i++ < limit))
it add some operations like: read regisger, &, &&.
So the time may exceed MMC_TIMEOUT_MS.
I used those code to test and found it's ok:
for (i = 0 ; i < 10; i++){
	if (!(OMAP_HSMMC_READ(host->base, SYSCTL) & bit))
		  break;
	j = limit/10;
	while(j--)
		cpu_relax();
}

Using this the problom can't occur.
Am i missing something?

Thanks!
Jianpeng Ma