This started out as a request to look at the DMA mask situation, and how to solve the issues which we have on ARM - notably how the DMA mask should be setup.
However, I started off reviewing how the dma_mask and coherent_dma_mask was being used, and what I found was rather messy, and in some cases rather buggy. I tried to get some of the bug fixes in before the last merge window, but it seems that the maintainers preferred to have the full solution rather than a simple -rc suitable bug fix.
So, this is an attempt to clean things up.
The first point here is that drivers performing DMA should be calling dma_set_mask()/dma_set_coherent_mask() in their probe function to verify that DMA can be performed. Lots of ARM drivers omit this step; please refer to the DMA API documentation on this subject.
What this means is that the DMA mask provided by bus code is a default value - nothing more. It doesn't have to accurately reflect what the device is actually capable of. Apart from the storage for dev->dma_mask being initialised for any device which is DMA capable, there is no other initialisation which is strictly necessary at device creation time.
Now, these cleanups address two major areas: 1. The setting of DMA masks, particularly when both the coherent and streaming DMA masks are set together.
2. The initialisation of DMA masks by drivers - this seems to be becoming a popular habbit, one which may not be entirely the right solution. Rather than having this scattered throughout the tree, I've pulled that into a central location (and called it coercing the DMA mask - because it really is about forcing the DMA mask to be that value.)
3. Finally, addressing the long held misbelief that DMA masks somehow correspond with physical addresses. We already have established long ago that dma_addr_t values returned from the DMA API are the values which you program into the DMA controller, and so are the bus addresses. It is _only_ sane that DMA masks are also bus related too, and not related to physical address spaces.
(3) is a very important point for LPAE systems, which may still have less than 4GB of memory, but this memory is all located above the 4GB physical boundary. This means with the current model, any device using a 32-bit DMA mask fails - even though the DMA controller is still only a 32-bit DMA controller but the 32-bit bus addresses map to system memory. To put it another way, the bus addresses have a 4GB physical offset on them.
This email is only being sent to the mailing lists in question, not to anyone personally. The list of individuals is far to great to do that. I'm hoping no mailing lists reject the patches based on the number of recipients.
Patches based on v3.12-rc1.
Documentation/DMA-API-HOWTO.txt | 37 +++++++++------ Documentation/DMA-API.txt | 8 +++ arch/arm/include/asm/dma-mapping.h | 8 +++ arch/arm/mm/dma-mapping.c | 49 ++++++++++++++++++-- arch/arm/mm/init.c | 12 +++--- arch/arm/mm/mm.h | 2 + arch/powerpc/kernel/vio.c | 3 +- block/blk-settings.c | 8 ++-- drivers/amba/bus.c | 6 +-- drivers/ata/pata_ixp4xx_cf.c | 5 ++- drivers/ata/pata_octeon_cf.c | 5 +- drivers/block/nvme-core.c | 10 ++--- drivers/crypto/ixp4xx_crypto.c | 48 ++++++++++---------- drivers/dma/amba-pl08x.c | 5 ++ drivers/dma/dw/platform.c | 8 +-- drivers/dma/edma.c | 6 +-- drivers/dma/pl330.c | 4 ++ drivers/firmware/dcdbas.c | 23 +++++----- drivers/firmware/google/gsmi.c | 13 +++-- drivers/gpu/drm/exynos/exynos_drm_drv.c | 6 ++- drivers/gpu/drm/omapdrm/omap_dmm_tiler.c | 5 +- drivers/media/platform/omap3isp/isp.c | 6 +- drivers/media/platform/omap3isp/isp.h | 3 - drivers/mmc/card/queue.c | 3 +- drivers/mmc/host/sdhci-acpi.c | 5 +- drivers/net/ethernet/broadcom/b44.c | 3 +- drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c | 8 +--- drivers/net/ethernet/brocade/bna/bnad.c | 13 ++---- drivers/net/ethernet/emulex/benet/be_main.c | 12 +---- drivers/net/ethernet/intel/e1000/e1000_main.c | 9 +--- drivers/net/ethernet/intel/e1000e/netdev.c | 18 +++----- drivers/net/ethernet/intel/igb/igb_main.c | 18 +++----- drivers/net/ethernet/intel/igbvf/netdev.c | 18 +++----- drivers/net/ethernet/intel/ixgb/ixgb_main.c | 16 ++----- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 15 ++---- drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c | 15 ++---- drivers/net/ethernet/nxp/lpc_eth.c | 6 ++- drivers/net/ethernet/octeon/octeon_mgmt.c | 5 +- drivers/net/ethernet/sfc/efx.c | 12 +----- drivers/net/wireless/b43/dma.c | 9 +--- drivers/net/wireless/b43legacy/dma.c | 9 +--- drivers/of/platform.c | 3 - drivers/parport/parport_pc.c | 8 +++- drivers/scsi/scsi_lib.c | 2 +- drivers/staging/dwc2/platform.c | 5 +- drivers/staging/et131x/et131x.c | 17 +------ drivers/staging/imx-drm/imx-drm-core.c | 8 +++- drivers/staging/imx-drm/ipuv3-crtc.c | 4 +- drivers/staging/media/dt3155v4l/dt3155v4l.c | 5 +-- drivers/usb/chipidea/ci_hdrc_imx.c | 7 +-- drivers/usb/dwc3/dwc3-exynos.c | 7 +-- drivers/usb/gadget/lpc32xx_udc.c | 4 +- drivers/usb/host/bcma-hcd.c | 3 +- drivers/usb/host/ehci-atmel.c | 7 +-- drivers/usb/host/ehci-octeon.c | 4 +- drivers/usb/host/ehci-omap.c | 10 ++-- drivers/usb/host/ehci-orion.c | 7 +-- drivers/usb/host/ehci-platform.c | 10 ++-- drivers/usb/host/ehci-s5p.c | 7 +-- drivers/usb/host/ehci-spear.c | 7 +-- drivers/usb/host/ehci-tegra.c | 7 +-- drivers/usb/host/ohci-at91.c | 9 ++-- drivers/usb/host/ohci-exynos.c | 7 +-- drivers/usb/host/ohci-nxp.c | 5 +- drivers/usb/host/ohci-octeon.c | 5 +- drivers/usb/host/ohci-omap3.c | 10 ++-- drivers/usb/host/ohci-pxa27x.c | 8 ++-- drivers/usb/host/ohci-sa1111.c | 6 +++ drivers/usb/host/ohci-spear.c | 7 +-- drivers/usb/host/ssb-hcd.c | 3 +- drivers/usb/host/uhci-platform.c | 7 +-- drivers/usb/musb/am35x.c | 50 +++++++-------------- drivers/usb/musb/da8xx.c | 49 +++++++------------- drivers/usb/musb/davinci.c | 48 +++++++------------- drivers/usb/musb/tusb6010.c | 49 +++++++------------- drivers/video/amba-clcd.c | 5 ++ include/linux/amba/bus.h | 2 - include/linux/dma-mapping.h | 31 +++++++++++++ sound/arm/pxa2xx-pcm.c | 9 +--- sound/soc/atmel/atmel-pcm.c | 11 ++--- sound/soc/blackfin/bf5xx-ac97-pcm.c | 11 ++--- sound/soc/blackfin/bf5xx-i2s-pcm.c | 10 ++--- sound/soc/davinci/davinci-pcm.c | 9 +--- sound/soc/fsl/fsl_dma.c | 9 +--- sound/soc/fsl/mpc5200_dma.c | 10 ++--- sound/soc/jz4740/jz4740-pcm.c | 12 ++--- sound/soc/kirkwood/kirkwood-dma.c | 9 +--- sound/soc/nuc900/nuc900-pcm.c | 9 ++-- sound/soc/omap/omap-pcm.c | 11 ++--- sound/soc/pxa/pxa2xx-pcm.c | 11 ++--- sound/soc/s6000/s6000-pcm.c | 9 +--- sound/soc/samsung/dma.c | 11 ++--- sound/soc/samsung/idma.c | 11 ++--- 93 files changed, 493 insertions(+), 566 deletions(-)