linux-kernel - Re: ata: For what PHY was debounce delay introduced? (was: [PATCH v3 3/3] ahci: AMD A85 FCH (Hudson D4): Skip 200 ms debounce delay in `sata_link

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Message-ID: <Ydiw8hxkNWDO2nW3@slm.duckdns.org>
Date:   Fri, 7 Jan 2022 11:30:26 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Jeff Garzik <jeff@...q.com>
Cc:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: ata: For what PHY was debounce delay introduced? (was: [PATCH v3
 3/3] ahci: AMD A85 FCH (Hudson D4): Skip 200 ms debounce delay in
 `sata_link_resume()`)

Hello,

On Wed, Jan 05, 2022 at 03:49:58PM -0500, Jeff Garzik wrote:
> On Tue, Jan 4, 2022 at 6:34 AM Paul Menzel <pmenzel@...gen.mpg.de> wrote:
> 
> > [cc: +jeff, +tejun]
> >
> > void sata_phy_reset(struct ata_port *ap)
> > {
> > […]
> >         /* wait for phy to become ready, if necessary */
> >         do {
> >                 msleep(200);
> >                 sstatus = scr_read(ap, SCR_STATUS);
> >                 if ((sstatus & 0xf) != 1)
> >                         break;
> >         } while (time_before(jiffies, timeout));
> > […]
> > }
> > ```
> >
> 
> The piix did not have SCRs, as I recall, so it wouldn't apply to those
> chips.   I don't recall further than that.
> 
> Presumably just give those early chips a "needs delay" quirk, and then
> start testing newer chips to make sure they survive an immediate bitbang?

I don't remember exactly but most likely the sata_sil chips, I think. But,
yeah, the way forward would be converting it to a quirk and gradually lift
them with tests.

Thanks and happy new year.

-- 
tejun