The refactor of powerpc DMA functions in commit 6666cc17d780 ("powerpc/dma: remove dma_nommu_mmap_coherent") incorrectly changes the way DMA mappings are handled on powerpc. Since this change, all mapped pages are marked as cache-inhibited through the default implementation of arch_dma_mmap_pgprot. This differs from the previous behavior of only marking pages in noncoherent mappings as cache-inhibited and has resulted in sporadic system crashes in certain hardware configurations and workloads (see Bugzilla).
This commit restores the previous correct behavior by providing an implementation of arch_dma_mmap_pgprot that only marks pages in noncoherent mappings as cache-inhibited. As this behavior should be universal for all powerpc platforms a new file, dma-generic.c, was created to store it. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204145 Fixes: 6666cc17d780 ("powerpc/dma: remove dma_nommu_mmap_coherent") Signed-off-by: Shawn Anastasio <sh...@anastas.io> --- arch/powerpc/Kconfig | 1 + arch/powerpc/kernel/Makefile | 3 ++- arch/powerpc/kernel/dma-common.c | 17 +++++++++++++++++ 3 files changed, 20 insertions(+), 1 deletion(-) create mode 100644 arch/powerpc/kernel/dma-common.c diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index d8dcd8820369..77f6ebf97113 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -121,6 +121,7 @@ config PPC select ARCH_32BIT_OFF_T if PPC32 select ARCH_HAS_DEBUG_VIRTUAL select ARCH_HAS_DEVMEM_IS_ALLOWED + select ARCH_HAS_DMA_MMAP_PGPROT select ARCH_HAS_ELF_RANDOMIZE select ARCH_HAS_FORTIFY_SOURCE select ARCH_HAS_GCOV_PROFILE_ALL diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 56dfa7a2a6f2..ea0c69236789 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -49,7 +49,8 @@ obj-y := cputable.o ptrace.o syscalls.o \ signal.o sysfs.o cacheinfo.o time.o \ prom.o traps.o setup-common.o \ udbg.o misc.o io.o misc_$(BITS).o \ - of_platform.o prom_parse.o + of_platform.o prom_parse.o \ + dma-common.o obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \ signal_64.o ptrace32.o \ paca.o nvram_64.o firmware.o diff --git a/arch/powerpc/kernel/dma-common.c b/arch/powerpc/kernel/dma-common.c new file mode 100644 index 000000000000..5a15f99f4199 --- /dev/null +++ b/arch/powerpc/kernel/dma-common.c @@ -0,0 +1,17 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Contains common dma routines for all powerpc platforms. + * + * Copyright (C) 2019 Shawn Anastasio (sh...@anastas.io) + */ + +#include <linux/mm.h> +#include <linux/dma-noncoherent.h> + +pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot, + unsigned long attrs) +{ + if (!dev_is_dma_coherent(dev)) + return pgprot_noncached(prot); + return prot; +} -- 2.22.0