On 02/22/2017 05:01 PM, Chen Feng wrote: > > > On 2017/2/22 3:29, Laura Abbott wrote: >> On 02/20/2017 10:05 PM, Chen Feng wrote: >>> Hi Laura, >>> >>> When we enable kernel v4.4 or newer version on our platform, we meet the issue >>> of flushing cache without reference device. It seems that this patch set is >>> a solution. I'm curious the progress of the discussion. Do you have any plan >>> to fix it in v4.4 and newer kernel verison? >>> >> >> No, I've abandoned this approach based on feedback. The APIs had too much >> potential for incorrect usage. I'm ripping out the implicit caching in Ion >> and switching it to a model where there should always be a device available. >> >> What's your use case where you don't have a device structure? >> > Userspace use ioctl to flush cache for device. > > ion_sync_for_device > dma_sync_sg_for_device(NULL, buffer->sg_table->sgl, > buffer->sg_table->nents, DMA_BIDIRECTIONAL); > > And sys-heap when allocate a zero buffer flush zero data to ddr. > alloc_buffer_page > ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order, > DMA_BIDIRECTIONAL); > > Yes, those calls are being removed. This is what I proposed back in December https://marc.info/?l=linux-kernel&m=148176054902921&w=2 I never heard any feedback on it so I assume everyone was okay with the general direction. I plan on pushing a revised and expanded version of that series once the merge window closes. Thanks, Laura > >> Thanks, >> Laura >> >>> On 2016/9/14 2:41, Laura Abbott wrote: >>>> On 09/13/2016 08:14 AM, Will Deacon wrote: >>>>> On Tue, Sep 13, 2016 at 08:02:20AM -0700, Laura Abbott wrote: >>>>>> On 09/13/2016 02:19 AM, Will Deacon wrote: >>>>>>> On Mon, Sep 12, 2016 at 02:32:56PM -0700, Laura Abbott wrote: >>>>>>>> >>>>>>>> arm64 may need to guarantee the caches are synced. Implement versions of >>>>>>>> the kernel_force_cache API to allow this. >>>>>>>> >>>>>>>> Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx> >>>>>>>> --- >>>>>>>> v3: Switch to calling cache operations directly instead of relying on >>>>>>>> DMA mapping. >>>>>>>> --- >>>>>>>> arch/arm64/include/asm/cacheflush.h | 8 ++++++++ >>>>>>>> arch/arm64/mm/cache.S | 24 ++++++++++++++++++++---- >>>>>>>> arch/arm64/mm/flush.c | 11 +++++++++++ >>>>>>>> 3 files changed, 39 insertions(+), 4 deletions(-) >>>>>>> >>>>>>> I'm really hesitant to expose these cache routines as an API solely to >>>>>>> support a driver sitting in staging/. I appreciate that there's a chicken >>>>>>> and egg problem here, but we *really* don't want people using these routines >>>>>>> in preference to the DMA API, and I fear that we'll simply grow a bunch >>>>>>> more users of these things if we promote it as an API like you're proposing. >>>>>>> >>>>>>> Can the code not be contained under staging/, as part of ion? >>>>>>> >>>>>> >>>>>> I proposed that in V1 and it was suggested I make it a proper API >>>>>> >>>>>> http://www.mail-archive.com/driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx/msg47654.html >>>>>> http://www.mail-archive.com/driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx/msg47672.html >>>>> >>>>> :/ then I guess we're in disagreement. If ion really needs this stuff >>>>> (which I don't fully grok), perhaps we should be exposing something at >>>>> a higher level from the architecture, so it really can't be used for >>>>> anything other than ion. >>>> >>>> I talked/complained about this at a past plumbers. The gist is that Ion >>>> ends up acting as a fake DMA layer for clients. It doesn't match nicely >>>> because clients can allocate both coherent and non-coherent memory. >>>> Trying to use dma_map doesn't work because a) a device for coherency isn't >>>> known at allocation time b) it kills performance. Part of the motivation >>>> for taking this approach is to avoid the need to rework the existing >>>> Android userspace and keep the existing behavior, as terrible as it >>>> is. Having Ion out of staging and not actually usable isn't helpful. >>>> >>>> I'll give this all some more thought and hopefully have one or two more >>>> proposals before Connect/Plumbers. >>>> >>>>> >>>>> Will >>>>> >>>> >>>> Thanks, >>>> Laura >>>> _______________________________________________ >>>> Linaro-mm-sig mailing list >>>> Linaro-mm-sig@xxxxxxxxxxxxxxxx >>>> https://lists.linaro.org/mailman/listinfo/linaro-mm-sig >>> >>> >>> _______________________________________________ >>> linux-arm-kernel mailing list >>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>> >> >> >> . >> > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
