<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Am 10.01.19 um 14:31 schrieb Bas Vermeulen:<br>
</div>
<blockquote type="cite" cite="mid:CAGtoiRiY-TK+_YHwk=f_2vMxJJ6Ucv9AQ2vuoxtufFakKp=hAA@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">On Thu, Jan 10, 2019 at 11:59 AM Christian König <<a href="mailto:ckoenig.leichtzumerken@gmail.com" moz-do-not-send="true">ckoenig.leichtzumerken@gmail.com</a>> wrote:<br>
</div>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<div class="gmail-m_9195313590891012054moz-cite-prefix">
<blockquote type="cite">The PCI Express controller as instantiated on this chip does not support hardware coherency. All incoming PCI Express transactions are made non IO-coherent.
<div><br>
</div>
<div>Would AMDGPU still work with that PCI Express controller, or is this a show-stopper?</div>
</blockquote>
<br>
I'm really wondering what this comment in the documentation means.<br>
<br>
As far as I know PCIe doesn't support cache coherency in the downstream and supporting it in the up stream is a must have.<br>
</div>
</div>
</blockquote>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<div class="gmail-m_9195313590891012054moz-cite-prefix">So what exactly is meant here with IO-coherent?<br>
</div>
</div>
</blockquote>
<div><br>
</div>
<div>I believe IO Coherent means that when PCIe writes something to CPU memory, the caches are flushed or updated<br>
(or in this case they aren't). I found <a href="https://community.arm.com/processors/b/blog/posts/extended-system-coherency---part-1---cache-coherency-fundamentals" moz-do-not-send="true">https://community.arm.com/processors/b/blog/posts/extended-system-coherency---part-1---cache-coherency-fundamentals</a> </div>
<div>with this explanation.</div>
</div>
</div>
</div>
</blockquote>
<br>
Yeah, but as I said this upstream memory coherency is mandatory for PCIe.<br>
<br>
When a controller doesn't have that it can't call itself a PCIe controller. The spec is pretty clear about that :)<br>
<br>
And to answer the original question: Yes, that would be a totally show-stopper.<br>
<br>
Regards,<br>
Christian.<br>
<br>
<blockquote type="cite" cite="mid:CAGtoiRiY-TK+_YHwk=f_2vMxJJ6Ucv9AQ2vuoxtufFakKp=hAA@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">
<div class="gmail_quote">
<div><br>
</div>
<div>Regards,</div>
<div><br>
</div>
<div>Bas Vermeulen</div>
</div>
</div>
</div>
</blockquote>
<br>
</body>
</html>