Re: pata_sl82c105 can not reserve IO region

[Alan <alan@lxorguk.ukuu.org.uk>]

On Sun, 3 Dec 2006 23:24:49 +0100 (MET)
Olaf Hering <olaf@aepfle.de> wrote:

> This change seems to fix it, only a single reset occurs. I think that
> one is normal when a CD is in the drive during bootup, maybe it leaves
> the drive in a confused state.
> 
> @@ -167,9 +175,13 @@ static void sl82c105_reset_engine(struct
>         struct pci_dev *pdev = to_pci_dev(ap->host->dev);
>         u16 val;
> 
> +       udelay(42);
>         pci_read_config_word(pdev, 0x7E, &val);
> +       udelay(10);
>         pci_write_config_word(pdev, 0x7E, val | 4);
> +       udelay(10);
>         pci_write_config_word(pdev, 0x7E, val & ~4);
> +       udelay(42);
>  }

Where do you get the delays from ? There is nothing in the documentation
or errata sheets I have here on that subject. Is this guesswork, divine
inspiration or an errata note I don't posess ?

In the absence of documented behaviour its seem to me much more likely
that the delay is actually either moving a race condition in the libata
code, or perhaps just allowing some time for the CD to "recover" in which
case it's perhaps a bit of a delay we need in libata. That would explain
why the old -> new change broke stuff.

Either way its most interesting it makes a difference.

Alan