Re: How to make SATA hotplug path tight?

[Tejun Heo <htejun@gmail.com>]

[adding linux-ide back, please don't drop it]

Fajun Chen wrote:
> Hi Tejun,
> 
> I try to understand your eh code and still have several questions:
> 
> 1. Why software is needed after hard reset under certain condition?

Because some controllers including sil24 cannot acquire device signature 
after hardreset.

>     rc = ata_do_reset(ap, reset, classes);
>     did_followup_srst = 0;
>     if (reset == hardreset &&
>         ata_eh_followup_srst_needed(rc, classify, classes)) {
>         /* okay, let's do follow-up softreset */
>         did_followup_srst = 1;
>         reset = softreset;
>       ...
>       Sometimes this part of the code costed as many as 7 secs:
> [  366.400000] ata2: hard resetting port
> [  366.400000] sata_phy_debounce: ENTER
> [  368.490000] sata_phy_debounce: EXIT
> [  368.490000] sil24_softreset: ENTER
> [  375.750000] ata_dev_classify: found ATA device by sig
> [  375.750000] sil24_softreset: EXIT, class=1
>       Is there any way to get drive going without going through this?

Well, on hotplug case, you need to detect which class of device is 
attached, so you need a softreset there.

> 2.  What's the concept of port suspend and resume?

Port being suspended and resumed, I think. :-) You need ask more 
specifically.

-- 
tejun