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From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Robin Murphy <robin.murphy@arm.com>, Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org, Matthias Brugger <mbrugger@suse.com>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	etnaviv@lists.freedesktop.org, linux-tegra@vger.kernel.org,
	Florian Fainelli <f.fainelli@gmail.com>,
	Stefan Wahren <wahrenst@gmx.net>,
	james.quinlan@broadcom.com, linux-pci@vger.kernel.org,
	"open list:DMA GENERIC OFFLOAD ENGINE SUBSYSTEM" 
	<dmaengine@vger.kernel.org>,
	xen-devel@lists.xenproject.org,
	Dan Williams <dan.j.williams@intel.com>,
	freedreno <freedreno@lists.freedesktop.org>,
	Frank Rowand <frowand.list@gmail.com>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>,
	Linux Media Mailing List <linux-media@vger.kernel.org>
Subject: Re: [PATCH 00/11] of: Fix DMA configuration for non-DT masters
Date: Wed, 25 Sep 2019 17:30:10 +0200
Message-ID: <43fb5fe1de317d65a4edf592f88ea150c6e3b8cc.camel@suse.de> (raw)
In-Reply-To: <e404c65b-5a66-6f91-5b38-8bf89a7697b2@arm.com>

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On Wed, 2019-09-25 at 16:09 +0100, Robin Murphy wrote:
> On 25/09/2019 15:52, Nicolas Saenz Julienne wrote:
> > On Tue, 2019-09-24 at 16:59 -0500, Rob Herring wrote:
> > > On Tue, Sep 24, 2019 at 1:12 PM Nicolas Saenz Julienne
> > > <nsaenzjulienne@suse.de> wrote:
> > > > 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.
> > 
> > > 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


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  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-24 18:12 Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 01/11] of: address: clean-up unused variable in of_dma_get_range() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 02/11] of: base: introduce __of_n_*_cells_parent() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 03/11] of: address: use parent DT node in bus->count_cells() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 04/11] of: address: introduce of_translate_dma_address_parent() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 05/11] of: expose __of_get_dma_parent() to OF subsystem Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 06/11] of: address: use parent OF node in of_dma_get_range() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 07/11] dts: arm64: layerscape: add dma-ranges property to qoric-mc node Nicolas Saenz Julienne
2019-10-14  8:28   ` Shawn Guo
2019-10-14 10:00     ` Nicolas Saenz Julienne
2019-10-14 11:09       ` Shawn Guo
2019-09-24 18:12 ` [PATCH 08/11] dts: arm64: layerscape: add dma-ranges property to pcie nodes Nicolas Saenz Julienne
2019-10-14  8:29   ` Shawn Guo
2019-09-24 18:12 ` [PATCH 09/11] of: device: remove comment in of_dma_configure() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 10/11] of: device: introduce of_dma_configure_parent() Nicolas Saenz Julienne
2019-09-24 18:12 ` [PATCH 11/11] of: simplify of_dma_config()'s arguments Nicolas Saenz Julienne
2019-09-24 21:59 ` [PATCH 00/11] of: Fix DMA configuration for non-DT masters Rob Herring
2019-09-25 14:52   ` Nicolas Saenz Julienne
2019-09-25 15:09     ` Robin Murphy
2019-09-25 15:30       ` Nicolas Saenz Julienne [this message]
2019-09-25 16:16         ` Rob Herring
2019-09-25 16:52           ` Robin Murphy
2019-09-25 21:33             ` Rob Herring
2019-09-26 10:44               ` Nicolas Saenz Julienne
2019-09-26 11:20                 ` Robin Murphy
2019-10-02 18:28                   ` Florian Fainelli
2019-09-25 16:07     ` Rob Herring

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