Re: [PATCH 2/5] sata_mv clean up mv_stop_edma usage

[Mark Lord <liml@rtr.ca>]

Jeff Garzik wrote:
> Mark Lord wrote:
>> Tejun Heo wrote:
>>> Hello, Mark.
>>>
>>> Mark Lord wrote:
>>>> -    /* now properly wait for the eDMA to stop */
>>>> -    for (i = 1000; i > 0; i--) {
>>>> -        reg = readl(port_mmio + EDMA_CMD_OFS);
>>>> +    /* Wait for the chip to confirm eDMA is off. */
>>>> +    for (i = 10000; i > 0; i--) {
>>>> +        u32 reg = readl(port_mmio + EDMA_CMD_OFS);
>>>>         if (!(reg & EDMA_EN))
>>>> -            break;
>>>> -
>>>> -        udelay(100);
>>>> -    }
>>>> -
>>>> -    if (reg & EDMA_EN) {
>>>> -        ata_port_printk(ap, KERN_ERR, "Unable to stop eDMA\n");
>>>> -        err = -EIO;
>>>> +            return 0;
>>>> +        udelay(10);
>>>
>>> Unless the hardware calls for really short polling interval, I think 
>>> it's generally better to limit polling with jiffies and using 
>>> msleep() instead of delays.
>> ..
>>
>> Oh, absolutely.  I was just leaving Jeff's (?) original udelay() in there
>> for now, to avoid another possible failure while testing the new stuff.
>>
>> But if we can *guarantee* that .qc_issue and .port_stop are
>> always invoked only from thread context, then.. no problemo.
> 
> qc_issue is inside spin_lock_irqsave()
..

Okay, let's leave it alone for now.
Perhaps later it can be reworked again to find
a way to busy wait without messing up other stuff.

Nearly all of the time it exits rapidly anyway.

Cheers