From: Robin Murphy <firstname.lastname@example.org>
To: Soeren Moch <email@example.com>, Shawn Lin <firstname.lastname@example.org>
Cc: Lorenzo Pieralisi <email@example.com>,
Andrew Murray <firstname.lastname@example.org>,
Bjorn Helgaas <email@example.com>,
Heiko Stuebner <firstname.lastname@example.org>,
Subject: Re: [BUG] PCI: rockchip: rk3399: pcie switch support
Date: Tue, 14 Apr 2020 13:28:05 +0100 [thread overview]
Message-ID: <email@example.com> (raw)
On 2020-04-14 12:35 pm, Soeren Moch wrote:
> On 06.04.20 19:12, Soeren Moch wrote:
>> On 06.04.20 14:52, Robin Murphy wrote:
>>> On 2020-04-04 7:41 pm, Soeren Moch wrote:
>>>> I want to use a PCIe switch on a RK3399 based RockPro64 V2.1 board.
>>>> "Normal" PCIe cards work (mostly) just fine on this board. The PCIe
>>>> switches (I tried Pericom and ASMedia based switches) also work fine on
>>>> other boards. The RK3399 PCIe controller with pcie_rockchip_host driver
>>>> also recognises the switch, but fails to initialize the buses behind the
>>>> bridge properly, see syslog from linux-5.6.0.
>>>> Any ideas what I do wrong, or any suggestions what I can test here?
>>> See the thread here:
>> Thanks Robin!
>> I also found out in the meantime that device enumeration fails in this
>> fatal way when probing non-existent devices. So if I hack my complete
>> bus topology into rockchip_pcie_valid_device, then all existing devices
>> come up properly. Of course this is not how PCIe should work.
>>> The conclusion there seems to be that the RK3399 root complex just
>>> doesn't handle certain types of response in a sensible manner, and
>>> there's not much that can reasonably be done to change that.
>> Hm, at least there is the promising suggestion to take over the SError
>> handler, maybe in ATF, as workaround.
> Unfortunately it seems to be not that easy. Only when PCIe device
> probing runs on one of the Cortex-A72 cores of rk3399 we see the SError.
> When probing runs on one of the A53 cores, we get a synchronous external
> abort instead.
> Is this expected to see different error types on big.LITTLE systems? Or
> is this another special property of the rk3399 pcie controller?
As far as I'm aware, the CPU microarchitecture is indeed one of the
factors in whether it takes a given external abort synchronously or
asynchronously, so yes, I'd say that probably is expected. I wouldn't
necessarily even rely on a single microarchitecture only behaving one
way, since in principle it's possible that surrounding instructions
might affect whether the core still has enough context left to take the
exception synchronously or not at the point the abort does come back.
In general external aborts are a "should never happen" kind of thing, so
they're not necessarily expected to be recoverable (I think the RAS
extensions might add a more robustness in terms of reporting, but aren't
relevant here either way).
At this point I'm starting to wonder whether it might be possible to do
something similar to the Arm N1SDP workaround using the Cortex-M0,
albeit with the complication that probing would realistically have to be
explicitly invoked from the Linux driver due to clocks and external
next prev parent reply other threads:[~2020-04-14 12:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-04 18:41 [BUG] PCI: rockchip: rk3399: pcie switch support Soeren Moch
2020-04-06 12:52 ` Robin Murphy
2020-04-06 17:12 ` Soeren Moch
2020-04-14 11:35 ` Soeren Moch
2020-04-14 12:28 ` Robin Murphy [this message]
2020-04-27 19:32 ` Soeren Moch
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).