Messages in this thread | | | Date | Tue, 30 Aug 2022 16:36:19 +0100 | Subject | Re: [PATCH 0/3] More ARM DMA ops cleanup | From | Robin Murphy <> |
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On 2022-08-30 16:19, Yongqin Liu wrote: > Hi, Robin > > Thanks for the kind reply! > > On Tue, 30 Aug 2022 at 17:48, Robin Murphy <robin.murphy@arm.com> wrote: >> >> On 2022-08-27 13:24, Yongqin Liu wrote: >>> Hi, Robin, Christoph >>> >>> With the changes landed in the mainline kernel, >>> one problem is exposed with our out of tree pvr module. >>> Like the source here[1], arm_dma_ops.sync_single_for_cpu is called in >>> the format like the following: >>> arm_dma_ops.sync_single_for_cpu(NULL, pStart, pEnd - pStart, >>> DMA_FROM_DEVICE); >>> >>> Not sure if you could give some suggestions on what I should do next >>> to make the pvr module work again. >> >> Wow, that driver reinvents so many standard APIs for no apparent reason >> it's not even funny. >> >> Anyway, from a brief look it seemingly already knows how to call the DMA >> API semi-correctly, so WTF that's doing behind an #ifdef, who knows? >> However it's still so completely wrong in general - fundamentally broken >> AArch64 set/way cache maintenance!? - that it looks largely beyond help. >> "Throw CONFIG_DMA_API_DEBUG at it and cry" is about the extent of >> support I'm prepared to provide for that mess. > > For the moment, I do not care about the AArch64 lines, like if we only > say the following two lines: > arm_dma_ops.sync_single_for_device(NULL, pStart, pEnd - pStart, > DMA_TO_DEVICE); > arm_dma_ops.sync_single_for_cpu(NULL, pStart, pEnd - pStart, > DMA_FROM_DEVICE); > > Could you please give some suggestions for that?
Remove them. Then remove the #ifdef __arch64__ too, since the code under there is doing a passable impression of generic DMA API usage, as long as one ignores the bigger picture.
arm64 already uses dma-direct. To say you don't care about the arm64 code when asking how to deal with ARM having now been converted to use dma-direct as well is supremely missing the point.
Robin. > > Thanks, > Yongqin Liu > > >>> Thanks in advance! >>> >>> [1]: https://android-git.linaro.org/kernel/omap-modules.git/tree/pvr/services4/srvkm/env/linux/osfunc.c?h=android-mainline#n4615 >>> >>> Thanks, >>> Yongqin Liu >>> >>> On Thu, 21 Apr 2022 at 22:35, Robin Murphy <robin.murphy@arm.com> wrote: >>>> >>>> On 2022-04-21 15:13, Christoph Hellwig wrote: >>>>> On Thu, Apr 21, 2022 at 12:36:56PM +0100, Robin Murphy wrote: >>>>>> Hi all, >>>>>> >>>>>> Thanks to Christoph's latest series, I'm reminded that, if we're going >>>>>> to give the ARM DMA ops some cleanup this cycle, it's as good a time as >>>>>> any to dust off these old patches and add them on top as well. I've >>>>>> based these on the arm-dma-direct branch which I assume matches the >>>>>> patches posted at [1]. >>>>> >>>>> All these do look sensible to me. But weren't you working on replacing >>>>> the ARM iommu dma_ops with dma-іommu anyway? >>>> >>>> Yes, that's somewhat entangled with the IOMMU bus ops stuff, so I'll >>>> probably get to the point of having to revisit it in a couple of months >>>> or so. These patches are off the bottom of that stack from my first >>>> attempt, where the aim was to make the current ops the same shape first >>>> so that the switch is then easier to reason about (particularly in terms >>>> of sounding out any issues with the hooking up of dev->dma_coherent, >>>> although your series will now be taking most of the load off there). >>>> >>>> Cheers, >>>> Robin. >>> >>> >>> > > >
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