[PATCH 00/18] BCM2835 DMA mapping cleanups and fixes

Dave Stevenson
2024-05-24T18:27:52Z

Hi All

This series initially cleans up the BCM2835 DMA driver in preparation for
supporting the 40bit version. It then fixes up the incorrect mapping behaviour
we've had to date.

The cleanups are based on Stefan Wahren's RFC [1], with a couple of minor bugs
fixed, but stopping before actually adding the 40bit support. If we can sort
the mapping issue, it avoids having to have workarounds in the 40bit support.

The mapping issues were discussed in [2].
Up until this point all DMA users have been passing in dma addresses rather than
CPU physical addresses, and the DMA driver has been using those directly rather
than using dma_map_resource() to map them.
The DT has also been missing some of the required mappings in "dma-ranges", but
they have been present in "ranges". I've therefore duplicated the minimum amount
of of_dma_get_range and translate_phys_to_dma to be able to use "ranges" as
discussed in that thread. I'm assuming that sort of code is not desirable in the
core code as it shouldn't be necessary, so keeping it contained within a driver
is the better solution.

When Andrea posted our downstream patches in [3], Robin Murphy stated that
dma_map_resource is the correct API, but as it currently doesn't check the
dma_range_map we need Sergey Semin's patch [4].
There seemed to be no follow up over the implications of it. I've therefore
included it in the series at least for discussion. If it's not acceptable then
I'm not sure of the route forward in fixing this mapping issue.

I'm expecting there to be some discussion, but also acknowledge that merging this
will need to be phased with the patches 1-13 needing to be merged before any of
14-17, and then 18 merged last to remove the workaround. I suspect that's the
least of my worries though.

I will apologise in advance if I don't respond immediately to comments - I'm
out of the office for the next week, but do appreciate any feedback.

Thanks
Dave

[1] https://lore.kernel.org/linux-arm-kernel/13ec386b-2305-27da-9765-8fa3ad71146c@i2se.com/T/
[2] https://lore.kernel.org/linux-arm-kernel/CAPY8ntBua=wPVUj+SM0WGcUL0fT56uEHo8YZUTMB8Z54X_aPRw@mail.gmail.com/T/
[3] https://lore.kernel.org/lkml/cover.1706948717.git.andrea.porta@suse.com/T/
[4] https://lore.kernel.org/linux-iommu/20220610080802.11147-1-Sergey.Semin@baikalelectronics.ru/

Dave Stevenson (7):
ARM: dts: bcm283x: Update to use dma-channel-mask
dmaengine: bcm2835: Add function to handle DMA mapping
dmaengine: bcm2835: Add backwards compatible handling until clients
updated
dmaengine: bcm2835: Use dma_map_resource to map addresses
dmaengine: bcm2835: Read ranges if dma-ranges aren't mapped
arm: dt: Add dma-ranges to the bcm283x platforms
dmaengine: bcm2835: Revert the workaround for DMA addresses

Phil Elwell (4):
mmc: bcm2835: Use phys addresses for slave DMA config
spi: bcm2835: Use phys addresses for slave DMA config
drm/vc4: Use phys addresses for slave DMA config
ASoC: bcm2835-i2s: Use phys addresses for DAI DMA

Serge Semin (1):
dma-direct: take dma-ranges/offsets into account in resource mapping

Stefan Wahren (6):
dmaengine: bcm2835: Support common dma-channel-mask
dmaengine: bcm2835: move CB info generation into separate function
dmaengine: bcm2835: move CB final extra info generation into function
dmaengine: bcm2835: make address increment platform independent
dmaengine: bcm2385: drop info parameters
dmaengine: bcm2835: pass dma_chan to generic functions

arch/arm/boot/dts/broadcom/bcm2711.dtsi | 14 +-
.../arm/boot/dts/broadcom/bcm2835-common.dtsi | 2 +-
arch/arm/boot/dts/broadcom/bcm2835.dtsi | 3 +-
arch/arm/boot/dts/broadcom/bcm2836.dtsi | 3 +-
arch/arm/boot/dts/broadcom/bcm2837.dtsi | 3 +-
drivers/dma/bcm2835-dma.c | 432 ++++++++++++++----
drivers/gpu/drm/vc4/vc4_hdmi.c | 15 +-
drivers/mmc/host/bcm2835.c | 17 +-
drivers/spi/spi-bcm2835.c | 23 +-
kernel/dma/direct.c | 2 +-
sound/soc/bcm/bcm2835-i2s.c | 18 +-
11 files changed, 383 insertions(+), 149 deletions(-)

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2.34.1