Em Mon, 14 May 2018 07:35:03 -0300 Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx> escreveu: > Hi Fabien, > > Em Mon, 14 May 2018 08:00:37 +0000 > Fabien DESSENNE <fabien.dessenne@xxxxxx> escreveu: > > > On 07/05/18 17:19, Mauro Carvalho Chehab wrote: > > > Em Mon, 07 May 2018 16:26:08 +0300 > > > Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> escreveu: > > > > > >> Hi Mauro, > > >> > > >> On Saturday, 5 May 2018 19:08:15 EEST Mauro Carvalho Chehab wrote: > > >>> There was a recent discussion about the use/abuse of GFP_DMA flag when > > >>> allocating memories at LSF/MM 2018 (see Luis notes enclosed). > > >>> > > >>> The idea seems to be to remove it, using CMA instead. Before doing that, > > >>> better to check if what we have on media is are valid use cases for it, or > > >>> if it is there just due to some misunderstanding (or because it was > > >>> copied from some other code). > > >>> > > >>> Hans de Goede sent us today a patch stopping abuse at gspca, and I'm > > >>> also posting today two other patches meant to stop abuse of it on USB > > >>> drivers. Still, there are 4 platform drivers using it: > > >>> > > >>> $ git grep -l -E "GFP_DMA\\b" drivers/media/ > > >>> drivers/media/platform/omap3isp/ispstat.c > > >>> drivers/media/platform/sti/bdisp/bdisp-hw.c > > >>> drivers/media/platform/sti/hva/hva-mem.c > > > > Hi Mauro, > > > > The two STI drivers (bdisp-hw.c and hva-mem.c) are only expected to run > > on ARM platforms, not on x86. > > Since this thread deals with x86 & DMA trouble, I am not sure that we > > actually have a problem for the sti drivers. > > > > There are some other sti drivers that make use of this GFP_DMA flag > > (drivers/gpu/drm/sti/sti_*.c) and it does not seem to be a problem. > > > > Nevertheless I can see that the media sti drivers depend on COMPILE_TEST > > (which is not the case for the DRM ones). > > Would it be an acceptable solution to remove the COMPILE_TEST dependency? > > This has nothing to do with either x86 or COMPILE_TEST. The thing is > that there's a plan for removing GFP_DMA from the Kernel[1], as it was > originally meant to be used only by old PCs, where the DMA controllers > used only on the bottom 16 MB memory address (24 bits). IMHO, it is > very unlikely that any ARM SoC have such limitation. > > [1] https://lwn.net/Articles/753273/ (article will be freely available > on May, 17) Btw, you can also read about that at: https://lwn.net/Articles/753274/ > > Anyway, before the removal of GFP_DMA happens, I'd like to better > understand why we're using it at media, and if we can, instead, > set the DMA bit mask, just like almost all other media drivers > that require to confine DMA into a certain range do. In the case > of ARM, this is what we currently have: > > drivers/media/platform/exynos-gsc/gsc-core.c: vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32)); > drivers/media/platform/exynos4-is/fimc-core.c: vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32)); > drivers/media/platform/exynos4-is/fimc-is.c: vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32)); > drivers/media/platform/exynos4-is/fimc-lite.c: vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32)); > drivers/media/platform/mtk-mdp/mtk_mdp_core.c: vb2_dma_contig_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32)); > drivers/media/platform/omap3isp/isp.c: ret = dma_coerce_mask_and_coherent(isp->dev, DMA_BIT_MASK(32)); > drivers/media/platform/s5p-g2d/g2d.c: vb2_dma_contig_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32)); > drivers/media/platform/s5p-jpeg/jpeg-core.c: vb2_dma_contig_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32)); > drivers/media/platform/s5p-mfc/s5p_mfc.c: DMA_BIT_MASK(32)); > drivers/media/platform/s5p-mfc/s5p_mfc.c: DMA_BIT_MASK(32)); > drivers/media/platform/s5p-mfc/s5p_mfc.c: vb2_dma_contig_set_max_seg_size(dev, DMA_BIT_MASK(32)); > > > > > BR > > > > Fabien > > > > >>> drivers/media/spi/cxd2880-spi.c > > >>> > > >>> Could you please check if GFP_DMA is really needed there, or if it is > > >>> just because of some cut-and-paste from some other place? > > >> I started looking at that for the omap3isp driver but Sakari beat me at > > >> submitting a patch. GFP_DMA isn't needed for omap3isp. > > >> > > > Thank you both for looking into it. > > > > > > Regards, > > > Mauro > > > > > > > > > > > > Thanks, > > > Mauro > > > > Thanks, > Mauro Thanks, Mauro
