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Prabhakar <prabhakar.csengg@gmail.com> says:
From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
non-coherent DMA support for AX45MP
====================================
On the Andes AX45MP core, cache coherency is a specification option so it
may not be supported. In this case DMA will fail. To get around with this
issue this patch series does the below:
1] Andes alternative ports is implemented as errata which checks if the
IOCP is missing and only then applies to CMO errata. One vendor specific
SBI EXT (ANDES_SBI_EXT_IOCP_SW_WORKAROUND) is implemented as part of
errata.
Below are the configs which Andes port provides (and are selected by
RZ/Five):
- ERRATA_ANDES
- ERRATA_ANDES_CMO
OpenSBI patch supporting ANDES_SBI_EXT_IOCP_SW_WORKAROUND SBI is now
part v1.3 release.
2] Andes AX45MP core has a Programmable Physical Memory Attributes (PMA)
block that allows dynamic adjustment of memory attributes in the runtime.
It contains a configurable amount of PMA entries implemented as CSR
registers to control the attributes of memory locations in interest.
OpenSBI configures the PMA regions as required and creates a reserve memory
node and propagates it to the higher boot stack.
Currently OpenSBI (upstream) configures the required PMA region and passes
this a shared DMA pool to Linux.
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
pma_resv0@58000000 {
compatible = "shared-dma-pool";
reg = <0x0 0x58000000 0x0 0x08000000>;
no-map;
linux,dma-default;
};
};
The above shared DMA pool gets appended to Linux DTB so the DMA memory
requests go through this region.
3] We provide callbacks to synchronize specific content between memory and
cache.
4] RZ/Five SoC selects the below configs
- AX45MP_L2_CACHE
- DMA_GLOBAL_POOL
- ERRATA_ANDES
- ERRATA_ANDES_CMO
----------x---------------------x--------------------x---------------x----
* b4-shazam-merge:
soc: renesas: Kconfig: Select the required configs for RZ/Five SoC
cache: Add L2 cache management for Andes AX45MP RISC-V core
dt-bindings: cache: andestech,ax45mp-cache: Add DT binding documentation for L2 cache controller
riscv: mm: dma-noncoherent: nonstandard cache operations support
riscv: errata: Add Andes alternative ports
riscv: asm: vendorid_list: Add Andes Technology to the vendors list
Link: https://lore.kernel.org/r/20230818135723.80612-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Prabhakar <prabhakar.csengg@gmail.com> says:
From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
This patch series is a subset from Arnd's original series [0]. Ive just
picked up the bits required for RISC-V unification of cache flushing.
Remaining patches from the series [0] will be taken care by Arnd soon.
* b4-shazam-merge:
riscv: dma-mapping: switch over to generic implementation
riscv: dma-mapping: skip invalidation before bidirectional DMA
riscv: dma-mapping: only invalidate after DMA, not flush
Link: https://lore.kernel.org/r/20230816232336.164413-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Introduce support for nonstandard noncoherent systems in the RISC-V
architecture. It enables function pointer support to handle cache
management in such systems.
This patch adds a new configuration option called
"RISCV_NONSTANDARD_CACHE_OPS." This option is a boolean flag that
depends on "RISCV_DMA_NONCOHERENT" and enables the function pointer
support for cache management in nonstandard noncoherent systems.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com> # tyre-kicking on a d1
Reviewed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com> #
Link: https://lore.kernel.org/r/20230818135723.80612-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Add helper functions for cache wback/inval/clean and use them
arch_sync_dma_for_device()/arch_sync_dma_for_cpu() functions. The proposed
changes are in preparation for switching over to generic implementation.
Reorganization of the code is based on the patch (Link[0]) from Arnd.
For now I have dropped CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU check as this
will be enabled by default upon selection of RISCV_DMA_NONCOHERENT
and also dropped arch_dma_mark_dcache_clean().
Link[0]: https://lore.kernel.org/all/20230327121317.4081816-22-arnd@kernel.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20230816232336.164413-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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For a DMA_BIDIRECTIONAL transfer, the caches have to be cleaned
first to let the device see data written by the CPU, and invalidated
after the transfer to let the CPU see data written by the device.
riscv also invalidates the caches before the transfer, which does
not appear to serve any purpose.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20230816232336.164413-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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No other architecture intentionally writes back dirty cache lines into
a buffer that a device has just finished writing into. If the cache is
clean, this has no effect at all, but if a cacheline in the buffer has
actually been written by the CPU, there is a driver bug that is likely
made worse by overwriting that buffer.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20230816232336.164413-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Currently, riscv defines ARCH_DMA_MINALIGN as L1_CACHE_BYTES, I.E
64Bytes, if CONFIG_RISCV_DMA_NONCOHERENT=y. To support unified kernel
Image, usually we have to enable CONFIG_RISCV_DMA_NONCOHERENT, thus
it brings some bad effects to coherent platforms:
Firstly, it wastes memory, kmalloc-96, kmalloc-32, kmalloc-16 and
kmalloc-8 slab caches don't exist any more, they are replaced with
either kmalloc-128 or kmalloc-64.
Secondly, larger than necessary kmalloc aligned allocations results
in unnecessary cache/TLB pressure.
This issue also exists on arm64 platforms. From last year, Catalin
tried to solve this issue by decoupling ARCH_KMALLOC_MINALIGN from
ARCH_DMA_MINALIGN, limiting kmalloc() minimum alignment to
dma_get_cache_alignment() and replacing ARCH_KMALLOC_MINALIGN usage
in various drivers with ARCH_DMA_MINALIGN etc.[1]
One fact we can make use of for riscv: if the CPU doesn't support
ZICBOM or T-HEAD CMO, we know the platform is coherent. Based on
Catalin's work and above fact, we can easily solve the kmalloc align
issue for riscv: we can override dma_get_cache_alignment(), then let
it return ARCH_DMA_MINALIGN at the beginning and return 1 once we know
the underlying HW neither supports ZICBOM nor supports T-HEAD CMO.
So what about if the CPU supports ZICBOM or T-HEAD CMO, but all the
devices are dma coherent? Well, we use ARCH_DMA_MINALIGN as the
kmalloc minimum alignment, nothing changed in this case. This case
can be improved in the future.
After this patch, a simple test of booting to a small buildroot rootfs
on qemu shows:
kmalloc-96 5041 5041 96 ...
kmalloc-64 9606 9606 64 ...
kmalloc-32 5128 5128 32 ...
kmalloc-16 7682 7682 16 ...
kmalloc-8 10246 10246 8 ...
So we save about 1268KB memory. The saving will be much larger in normal
OS env on real HW platforms.
Link: https://lore.kernel.org/linux-arm-kernel/20230524171904.3967031-1-catalin.marinas@arm.com/ [1]
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230718152214.2907-2-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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The noncoherent_supported indicates whether the HW is coherent or not,
it won't change after booting, mark it as __ro_after_init.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230614165504.532-4-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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riscv_cbom_block_size and riscv_init_cbom_blocksize() should always
be available and riscv_init_cbom_blocksize() should always be
invoked, even when compiling without RISCV_ISA_ZICBOM enabled. This
is because disabling RISCV_ISA_ZICBOM means "don't use zicbom
instructions in the kernel" not "pretend there isn't zicbom, even
when there is". When zicbom is available, whether the kernel enables
its use with RISCV_ISA_ZICBOM or not, KVM will offer it to guests.
Ensure we can build KVM and that the block size is initialized even
when compiling without RISCV_ISA_ZICBOM.
Fixes: 8f7e001e0325 ("RISC-V: Clean up the Zicbom block size probing")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Anup Patel <anup@brainfault.org>
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We're about to allow guests to use the Zicbom extension. KVM
userspace needs to know the cache block size in order to
properly advertise it to the guest. Provide a virtual config
register for userspace to get it with the GET_ONE_REG API, but
setting it cannot be supported, so disallow SET_ONE_REG.
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
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This fixes two issues: I truncated the warning's hart ID when porting to
the 64-bit hart ID code, and the original code's warning handling could
fire on an uninitialized hart ID.
The biggest change here is that riscv_cbom_block_size is no longer
initialized, as IMO the default isn't sane: there's nothing in the ISA
that mandates any specific cache block size, so falling back to one will
just silently produce the wrong answer on some systems. This also
changes the probing order so the cache block size is known before
enabling Zicbom support.
CC: stable@vger.kernel.org
CC: Andrew Jones <ajones@ventanamicro.com>
CC: Heiko Stuebner <heiko@sntech.de>
CC: Atish Patra <atishp@rivosinc.com>
Fixes: 3aefb2ee5bdd ("riscv: implement Zicbom-based CMO instructions + the t-head variant")
Fixes: 1631ba1259d6 ("riscv: Add support for non-coherent devices using zicbom extension")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
[Conor: fixed the redefinition errors]
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220912224800.998121-1-mail@conchuod.ie
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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This series is based on the alternatives changes done in my svpbmt
series and thus also depends on Atish's isa-extension parsing series.
It implements using the cache-management instructions from the Zicbom-
extension to handle cache flush, etc actions on platforms needing them.
SoCs using cpu cores from T-Head like the Allwinne D1 implement a
different set of cache instructions. But while they are different,
instructions they provide the same functionality, so a variant can easly
hook into the existing alternatives mechanism on those.
[Palmer: Some minor fixups, including a RISCV_ISA_ZICBOM dependency on
MMU that's probably not strictly necessary. The Zicbom support will
trip up sparse for users that have new toolchains, I just sent a patch.]
Link: https://lore.kernel.org/all/20220706231536.2041855-1-heiko@sntech.de/
Link: https://lore.kernel.org/linux-sparse/20220811033138.20676-1-palmer@rivosinc.com/T/#u
* palmer/riscv-zicbom:
riscv: implement cache-management errata for T-Head SoCs
riscv: Add support for non-coherent devices using zicbom extension
dt-bindings: riscv: document cbom-block-size
of: also handle dma-noncoherent in of_dma_is_coherent()
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The Zicbom ISA-extension was ratified in november 2021
and introduces instructions for dcache invalidate, clean
and flush operations.
Implement cache management operations for non-coherent devices
based on them.
Of course not all cores will support this, so implement an
alternative-based mechanism that replaces empty instructions
with ones done around Zicbom instructions.
As discussed in previous versions, assume the platform
being coherent by default so that non-coherent devices need
to get marked accordingly by firmware.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20220706231536.2041855-4-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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