Hi,
This is v5 of my Apple M1 DART IOMMU driver series as a follow up to the
previous
versions [1][2][3][7].
Short summary: this series adds support for the iommu found in Apple's new M1
SoC which is required to use DMA on most peripherals like the display
controller,
the USB ports or the internal PCIe bus (which is used for WiFi, Ethernet and
more USB ports).
So far this code has been tested by multiple people with dwc3 in host and
device mode (which both only require changes to the device tree after this
patchset) and PCIe (using a yet to be finalized patchset).
Note that this version has to be applied on top of iommu/core or iommu/next
since
it now uses the new map_pages/unmap_pages API.
== Testing this patchset with the USB-C controller ==
The two USB-C ports on the M1 machines are exposed as two separate dwc3
controllers which are behind a DART. Now that my USB phy bringup code has been
merged into our bootloader m1n1 you can easily test this patchset yourself:
1) Follow the instructions at [4] to setup our bootloader m1n1 on your M1
machine which will allow you to boot kernels using a normal USB cable.
Note that you'll still need a special setup to expose the UART for very
low-level debugging.
2) Apply this patchset and add the DART and dwc3 nodes as done in e.g. [5].
3) Boot the kernel through our bootloader m1n1. You'll need a version after
commit [6] which enables the USB PHY and the USB PD chip.
Note that the dwc3 controller has a quirk where each root port can only be used
once right now. The most stable way to test is to already connected the USB
device(s) before booting the kernel.
It's also possible to test the PCIe bus but this requires a more complex setup
for now. I can write a quick howto if anyone is interested though.
(tl;dr: Mark Kettenis has a u-boot fork that includes PCIe bringup code and
Marc Zyngier has a WIP patchset to add a PCIe driver)
== Project Blurb ==
Asahi Linux is an open community project dedicated to developing and
maintaining mainline support for Apple Silicon on Linux. Feel free to
drop by #asahi and #asahi-dev on OFTC to chat with us, or check
our website for more information on the project:
https://asahilinux.org/
== Changes ==
Changes for v5:
- Added reviewed-by and tested-by tags (thanks!)
- Rebased on top of iommu/core and replaced map/unmap with
map_pages/unmap_pages
- Removed software bypass hacks: I've tried a few different variants now
and they all have drawbacks or incompatibilities that I am not comfortable
with. This means that PCIe devices (for which there is no kernel support yet
anyway) will not work correctly for now on 4K kernels. I plan to address this
in a follow-up series where I want to modify the dma-iommu layer to support
pagesize mismatches.
- Removed reference to ARM from the constants for the io-pgtable code
- Addressed the following comments by Robin Murphy, which resulted in some
major
changes to apple-dart.c
- Correctly assign iommu_groups in apple_dart_device_group
- Get rid of the fwspec-inspired of_xlate linked lists and replaced them with
a simple static array with a streamid bitmap covering all known cases
- Relax locking: Now only a single spinlock around TLB flushes and a mutex
around domain initialization are required. attach_dev/detach_dev uses
atomic64_t.
- Set .suppress_bind_attrs to prevent manual unbinding
- Get rid of .shutdown since there's no real need to clean anything up
- Manage interrupts manually instead of using devm_* to prevent situations
where a shared interrupt could trigger while clocks are disabled
- apple_dart_irq now prints "unknown" when more than a single error bit
has been set.
- Use DL_FLAG_AUTOREMOVE_SUPPLIER so that there's no need to keep track
of the pointer
- Ignore any unknown protection flags instead of failing
- Use dev_err_ratelimited and clk_bulk_disable_unprepare instead of
open-coding them
- Correctly set and clear iommu_bus_ops
- Removed unhelpful WARN_ONs and duplicate sanity checks
- Removed unnecessary identity stream map reset code
- Renamed apple-dart-iommu.c to apple-dart.c
- Fixed commit style to use the correct subsystem style
- Possibly some smaller fixes I forgot about
Changes for v4:
- Addressed Rob Herring's remark about the incorrect phandles in the device
tree binding example and added his reviewed-by tag
- Take the software linear mapping range from the bus instead of hardcoding
it in the driver
- Use def_domain_type to force bypass mode if there's a pagesize mismatch
between the DART (hardwired to 16KB) and the kernel (may use 4K)
- Added lockdep_assert_held instead of comments as suggested by Rouven
Czerwinski
- rebased on 5.13-rc7
Changes for v3:
- fixed name of the iommu node in the device tree binding example
pointed out by Arnd Bergmann
- remove hardware specific checks from io-pgtable.c as pointed out by
