From: Bjorn Helgaas <helgaas@kernel.org>
To: yu <kkndyu@gmail.com>
Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Logan Gunthorpe <logang@deltatee.com>,
Stephen Bates <sbates@raithlin.com>,
Jonathan Cameron <jonathan.cameron@huawei.com>,
Eric Wehage <Eric.Wehage@huawei.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>
Subject: Re: How to force RC to forward p2p TLPs
Date: Fri, 28 Dec 2018 20:29:23 -0600 [thread overview]
Message-ID: <20181229022923.GA159477@google.com> (raw)
In-Reply-To: <CADayL-pxr_dpJykyiTeQDO13XmKPoKUs544zVrB2taHTVEx9Pw@mail.gmail.com>
[+cc Logan, Stephen, Jonathan, Eric, Alex]
On Sat, Dec 22, 2018 at 12:50:19PM +0800, yu wrote:
> Hi all,
>
> We have a PCIE card which has a PEX8732 switch on-board, and there
> are two endpoint SOCs like graphic decoder behind the switch, and by
> default the ACS is enabled in 8732.
>
> We use the p2p DMA to transfer data between these two endpoint SOCs,
> and if the host server is not enable ACS in BIOS, the p2p works well,
> but when ACS is enabled in BIOS, the p2p is always failed. With the
> help of a protocol analyzer, we can see that the TLP is redirected to
> RC, and RC just discard it.
>
> I tried to find how to make RC forward redirected TLP to its original
> target, but nothing found, it seems this is highly related to the RC
> vendors.
>
> In the PCIE 4.0 spec, the section of the RC behavior of the p2p
> request redirect said that ''implementation-specific logic within the
> RC that determines whether the request is directed towards its
> original target, or blocked as an ACS Violation error. the algorithms
> and specific controls for making this determination are not
> architected by this spec''.
>
>
> So is there some spec or document to describe how to set the RC? Any
> suggestion is appreciated.
Not that I'm aware of, but the folks I cc'd would know a lot more
about this area.
Bjorn
next prev parent reply other threads:[~2018-12-29 2:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-22 4:50 How to force RC to forward p2p TLPs yu
2018-12-29 2:29 ` Bjorn Helgaas [this message]
2018-12-29 19:18 ` Logan Gunthorpe
2019-01-01 6:20 ` Eric Wehage
2019-01-02 1:07 ` Stephen Bates
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