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@xxxxxxx> 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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