From: Stephen Douthit <stephend@silicom-usa.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
"linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ata: ahci: Lookup PCS register offset based on PCI device ID
Date: Mon, 19 Aug 2019 16:30:41 +0000 [thread overview]
Message-ID: <f6399f3a-3899-2663-6667-e967eb43b156@silicom-usa.com> (raw)
In-Reply-To: <CAPcyv4ivzdEKbVepxcyJMmDmb5zG4Zvw+3f0rVJ8FOErK+c27g@mail.gmail.com>
On 8/14/19 1:17 PM, Dan Williams wrote:
>> Can you get someone from the controller design team to give us a clear
>> answer on a revision where this PCS change happened?
>>
>> It would be nice if we could just check PCI_REVISION_ID or something
>> similar.
>
> I don't think such a reliable association with rev-id exists, the> intent was that the OS need never consider PCS.
Can you please ask to confirm? It would be a much simpler check if it
is possible.
> The way Linux is using
> it is already broken with the assumption that it is performed after
> every HOST_CTL based reset which only resets mmio space. At most it
> should only be required at initial PCI discovery iff platform firmware
> failed to run.
This is a separate issue.
It's broken in the sense that the code is called more often that it
needs to be, but reset isn't a hot path, and there are no side effects
to doing this multiple times that I can see. And as you point out, no
bug reports, so pretty benign all things considered.
We could move the PCS quirk code to ahci_init_one() to address this
concern once there's agreement on what the criteria is to run/not-run
this code.
> There are no bug reports with the current
> implementation that only attempts to enable bits based on PORTS_IMPL,
> so I think we are firmer ground trying to draw a line where the driver
> just stops worrying about PCS rather than try to detect the layout.
Someone at Intel is going to need to decide where/how to draw this line.
next prev parent reply other threads:[~2019-08-19 16:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 20:24 [PATCH] ata: ahci: Lookup PCS register offset based on PCI device ID Stephen Douthit
2019-08-09 3:46 ` Jens Axboe
2019-08-09 14:13 ` Stephen Douthit
2019-08-09 14:16 ` Jens Axboe
2019-08-10 7:43 ` Christoph Hellwig
2019-08-10 20:22 ` Dan Williams
2019-08-12 13:02 ` Stephen Douthit
2019-08-12 14:11 ` Jens Axboe
2019-08-12 16:29 ` Dan Williams
2019-08-12 17:49 ` Stephen Douthit
2019-08-12 18:06 ` Christoph Hellwig
2019-08-12 19:12 ` Stephen Douthit
2019-08-12 19:31 ` Dan Williams
2019-08-13 7:29 ` Christoph Hellwig
2019-08-13 22:07 ` Dan Williams
2019-08-14 14:34 ` Stephen Douthit
2019-08-14 16:09 ` Dan Williams
2019-08-14 16:54 ` Stephen Douthit
2019-08-14 17:17 ` Dan Williams
2019-08-19 16:30 ` Stephen Douthit [this message]
2019-08-20 2:17 ` Dan Williams
2019-08-20 13:59 ` Stephen Douthit
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