Re: [PATCH 10/12] libata-hp-prep: implement sata_phy_debounce()

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> Jeff Garzik wrote:
>> Tejun Heo wrote:
>>> With hotplug, PHY always needs to be debounced before a reset as any
>>> reset might find new devices.  Extract PHY waiting code from
>>> sata_phy_resume() and extend it to include SStatus debouncing.  Note
>>> that sata_phy_debounce() is superset of what used to be done inside
>>> sata_phy_resume().
>>>
>>> Three default debounce timing parameters are defined to be used by
>>> hot/boot plug.  As resume failure during probing will be properly
>>> handled as errors, timeout doesn't have to be long as before.
>>> probeinit() uses the same timeout to retain the original behavior.
>>>
>>> Signed-off-by: Tejun Heo <htejun@gmail.com>
>>
>> NAK, changes behavior.  We want to preserve the old order of 
>> operations because some PHYs (sata_via and sata_mv come to mind) are a 
>> bit sensitive to being pounded immediately after wakeup.
> 
> The following is what the original sata_phy_resume() did
> 
> 1. read SControl
> 2. write SControl (wake)
> 3. msleep(200)
> 4. read SStatus
> 5. if condition not met, goto #3
> 
> The new code does...
> 
> 1. read SControl
> 2. write SControl (wake)
> 3. read SStatus
> 4. msleep(interval_msec)
> 5. read SStatus
> 6. if condition not met, goto #4
> 
> How about putting msleep(200) before calling sata_phy_debounce() from 
> sata_phy_resume().  This will add msleep(200) between #2 and #3 and the 
> only difference left would be the duration of interval_msec in #4 which 
> is 5ms during boot, 25ms during EH.  The wait is in the millisecs range 
> and it's difficult to imagine the change would cause any problem.

As long as the delay following #2 remains, I'm happy...

	Jeff