On Wed, 2019-09-25 at 16:09 +0100, Robin Murphy wrote:

On 25/09/2019 15:52, Nicolas Saenz Julienne wrote:

quoted

On Tue, 2019-09-24 at 16:59 -0500, Rob Herring wrote:

quoted

On Tue, Sep 24, 2019 at 1:12 PM Nicolas Saenz Julienne
[off-list ref] wrote:

quoted

Hi All,
this series tries to address one of the issues blocking us from
upstreaming Broadcom's STB PCIe controller[1]. Namely, the fact that
devices not represented in DT which sit behind a PCI bus fail to get the
bus' DMA addressing constraints.

This is due to the fact that of_dma_configure() assumes it's receiving a
DT node representing the device being configured, as opposed to the PCIe
bridge node we currently pass. This causes the code to directly jump
into PCI's parent node when checking for 'dma-ranges' and misses
whatever was set there.

To address this I create a new API in OF - inspired from Robin Murphys
original proposal[2] - which accepts a bus DT node as it's input in
order to configure a device's DMA constraints. The changes go deep into
of/address.c's implementation, as a device being having a DT node
assumption was pretty strong.

On top of this work, I also cleaned up of_dma_configure() removing its
redundant arguments and creating an alternative function for the special
cases
not applicable to either the above case or the default usage.

IMO the resulting functions are more explicit. They will probably
surface some hacky usages that can be properly fixed as I show with the
DT fixes on the Layerscape platform.

This was also tested on a Raspberry Pi 4 with a custom PCIe driver and
on a Seattle AMD board.

Humm, I've been working on this issue too. Looks similar though yours
has a lot more churn and there's some other bugs I've found.

That's good news, and yes now that I see it, some stuff on my series is
overly
complicated. Specially around of_translate_*().

On top of that, you removed in of_dma_get_range():

-	/*
-	 * At least empty ranges has to be defined for parent node if
-	 * DMA is supported
-	 */
-	if (!ranges)
-		break;

Which I assumed was bound to the standard and makes things easier.

quoted

Can you test out this branch[1]. I don't have any h/w needing this,
but wrote a unittest and tested with modified QEMU.

I reviewed everything, I did find a minor issue, see the patch attached.

WRT that patch, the original intent of "force_dma" was purely to 
consider a device DMA-capable regardless of the presence of 
"dma-ranges". Expecting of_dma_configure() to do anything for a non-OF 
device has always been bogus - magic paravirt devices which appear out 
of nowhere and expect to be treated as genuine DMA masters are a 
separate problem that we haven't really approached yet.

I agree it's clearly abusing the function. I have no problem with the behaviour
change if it's OK with you.

Robin, have you looked into supporting multiple dma-ranges? It's the next thing
we need for BCM STB's PCIe. I'll have a go at it myself if nothing is in the
works already.

Regards,
Nicolas