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Message-ID: <572668b5-48b5-4bac-8712-75a5e2c096bd@linux-m68k.org>
Date: Thu, 19 Oct 2023 22:50:50 +1000
From: Greg Ungerer <gerg@...ux-m68k.org>
To: Christoph Hellwig <hch@....de>, iommu@...ts.linux.dev
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Conor Dooley <conor@...nel.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Magnus Damm <magnus.damm@...il.com>, Robin Murphy <robin.murphy@....com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>, Wei Fang <wei.fang@....com>,
Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
NXP Linux Team <linux-imx@....com>, linux-m68k@...ts.linux-m68k.org,
netdev@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-renesas-soc@...r.kernel.org, Jim Quinlan <james.quinlan@...adcom.com>
Subject: Re: [PATCH 09/12] m68k: use the coherent DMA code for coldfire
without data cache
Hi Christoph,
On 16/10/23 15:47, Christoph Hellwig wrote:
> Coldfire cores configured without a data cache are DMA coherent and
> should thus simply use the simple coherent version of dma-direct.
>
> Introduce a new COLDFIRE_COHERENT_DMA Kconfig symbol as a convenient
> short hand for such configurations, and a M68K_NONCOHERENT_DMA symbol
> for all cases where we need to build non-coherent DMA infrastructure
> to simplify the Kconfig and code conditionals.
>
> Not building the non-coherent DMA code slightly reduces the code
> size for such configurations.
>
> Numers for m5249evb_defconfig below:
>
> text data bss dec hex filename
> 2896158 401052 65392 3362602 334f2a vmlinux.before
> 2895166 400988 65392 3361546 334b0a vmlinux.after
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> arch/m68k/Kconfig | 8 ++++----
> arch/m68k/Kconfig.cpu | 12 ++++++++++++
> arch/m68k/kernel/Makefile | 2 +-
> arch/m68k/kernel/dma.c | 2 +-
> 4 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index 0430b8ba6b5cc6..6c585eae89f4dc 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -3,19 +3,19 @@ config M68K
> bool
> default y
> select ARCH_32BIT_OFF_T
> - select ARCH_DMA_ALLOC if !MMU || COLDFIRE
> + select ARCH_DMA_ALLOC if M68K_NONCOHERENT_DMA && COLDFIRE
> select ARCH_HAS_BINFMT_FLAT
> select ARCH_HAS_CPU_FINALIZE_INIT if MMU
> select ARCH_HAS_CURRENT_STACK_POINTER
> - select ARCH_HAS_DMA_PREP_COHERENT if HAS_DMA && MMU && !COLDFIRE
> - select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
> + select ARCH_HAS_DMA_PREP_COHERENT if M68K_NONCOHERENT_DMA && !COLDFIRE
> + select ARCH_HAS_SYNC_DMA_FOR_DEVICE if M68K_NONCOHERENT_DMA
> select ARCH_HAVE_NMI_SAFE_CMPXCHG if RMW_INSNS
> select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
> select ARCH_NO_PREEMPT if !COLDFIRE
> select ARCH_USE_MEMTEST if MMU_MOTOROLA
> select ARCH_WANT_IPC_PARSE_VERSION
> select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
> - select DMA_DIRECT_REMAP if HAS_DMA && MMU && !COLDFIRE
> + select DMA_DIRECT_REMAP if M68K_NONCOHERENT_DMA && !COLDFIRE
> select GENERIC_ATOMIC64
> select GENERIC_CPU_DEVICES
> select GENERIC_IOMAP
> diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu
> index b826e9c677b2ae..e8905d38c714c4 100644
> --- a/arch/m68k/Kconfig.cpu
> +++ b/arch/m68k/Kconfig.cpu
> @@ -535,3 +535,15 @@ config CACHE_COPYBACK
> The ColdFire CPU cache is set into Copy-back mode.
> endchoice
> endif # HAVE_CACHE_CB
> +
> +# Coldfire cores that do not have a data cache configured can do coherent DMA.
> +config COLDFIRE_COHERENT_DMA
> + bool
> + default y
> + depends on COLDFIRE
> + depends on !HAVE_CACHE_CB && !CONFIG_CACHE_D && !CONFIG_CACHE_BOTH
^^^^^^ ^^^^^^
This needs to be "depends on !HAVE_CACHE_CB && !CACHE_D && !CACHE_BOTH".
Regards
Greg
> +
> +config M68K_NONCOHERENT_DMA
> + bool
> + default y
> + depends on HAS_DMA && !COLDFIRE_COHERENT_DMA
> diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile
> index af015447dfb4c1..01fb69a5095f43 100644
> --- a/arch/m68k/kernel/Makefile
> +++ b/arch/m68k/kernel/Makefile
> @@ -23,7 +23,7 @@ obj-$(CONFIG_MMU_MOTOROLA) += ints.o vectors.o
> obj-$(CONFIG_MMU_SUN3) += ints.o vectors.o
> obj-$(CONFIG_PCI) += pcibios.o
>
> -obj-$(CONFIG_HAS_DMA) += dma.o
> +obj-$(CONFIG_M68K_NONCOHERENT_DMA) += dma.o
>
> obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
> obj-$(CONFIG_BOOTINFO_PROC) += bootinfo_proc.o
> diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
> index 2e192a5df949bb..f83870cfa79b37 100644
> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c
> @@ -17,7 +17,7 @@
>
> #include <asm/cacheflush.h>
>
> -#if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
> +#ifndef CONFIG_COLDFIRE
> void arch_dma_prep_coherent(struct page *page, size_t size)
> {
> cache_push(page_to_phys(page), size);
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