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@xxxxxx>
---
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);
