linux-kernel - [PATCH 1/2] m68k: Enable DMA support for Coldfire M5441x

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Message-Id: <20250121-coldfire-global-pool-v1-1-382a7235c2aa@yoseli.org>
Date: Tue, 21 Jan 2025 11:54:13 +0100
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>, 
 Greg Ungerer <gerg@...ux-m68k.org>
Cc: linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org, 
 Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
Subject: [PATCH 1/2] m68k: Enable DMA support for Coldfire M5441x

Add DMA support for the Coldfire M5441x platform with a global DMA pool
and coherent DMA operations.

Reserve a configurable DRAM pool (default 16MB with CONFIG_DMASIZE) and
initialize it with the dedicated helper.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
---
 arch/m68k/Kconfig.cpu       |  2 ++
 arch/m68k/Kconfig.machine   |  8 ++++++++
 arch/m68k/coldfire/Makefile |  2 ++
 arch/m68k/include/asm/dma.h |  1 +
 arch/m68k/kernel/dma.c      | 10 ++++++++++
 arch/m68k/mm/mcfmmu.c       |  5 +++++
 6 files changed, 28 insertions(+)

diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu
index c9a7e602d8a4da8e5094762e90c7b1a1ab1acfdf..66e5f62a0eb280f6029e7501f4fa152f422b76b4 100644
--- a/arch/m68k/Kconfig.cpu
+++ b/arch/m68k/Kconfig.cpu
@@ -303,6 +303,8 @@ config M5441x
 	select COLDFIRE_PIT_TIMER
 	select MMU_COLDFIRE if MMU
 	select HAVE_CACHE_CB
+	select DMA_GLOBAL_POOL
+	select ARCH_HAS_DMA_OPS
 	help
 	  Freescale Coldfire 54410/54415/54416/54417/54418 processor support.
 
diff --git a/arch/m68k/Kconfig.machine b/arch/m68k/Kconfig.machine
index de39f23b180ee21d3d3a028ad46f815f3690b1ad..1467d1ff349bb26714a3c99f593a2a71c9ad273d 100644
--- a/arch/m68k/Kconfig.machine
+++ b/arch/m68k/Kconfig.machine
@@ -405,6 +405,14 @@ config KERNELBASE
 	  a system with the RAM based at address 0, and leaving enough room
 	  for the theoretical maximum number of 256 vectors.
 
+config DMASIZE
+       hex "Size of DRAM (in bytes) reserved pool"
+       default "0x1000000"
+       depends on DMA_GLOBAL_POOL
+       help
+         Define the DMA pool size, allocated at init time, which can then
+         be used by DMA engine. Defaults to 16MB.
+
 comment "ROM configuration"
 
 config ROM
diff --git a/arch/m68k/coldfire/Makefile b/arch/m68k/coldfire/Makefile
index c56bc0dc7f2e338c8275cfd15656f80e78825254..b30c55ec722401822651cb329a9910cfc2d1d788 100644
--- a/arch/m68k/coldfire/Makefile
+++ b/arch/m68k/coldfire/Makefile
@@ -31,6 +31,8 @@ obj-$(CONFIG_M5407)	+= m5407.o intc.o reset.o
 obj-$(CONFIG_M54xx)	+= m54xx.o intc-2.o
 obj-$(CONFIG_M5441x)	+= m5441x.o intc-simr.o reset.o
 
+obj-$(CONFIG_ARCH_HAS_DMA_OPS) += dma_ops.o
+
 obj-$(CONFIG_COLDFIRE_PIT_TIMER) += pit.o
 obj-$(CONFIG_COLDFIRE_TIMERS)	 += timers.o
 obj-$(CONFIG_COLDFIRE_SLTIMERS)	 += sltimers.o
diff --git a/arch/m68k/include/asm/dma.h b/arch/m68k/include/asm/dma.h
index 1c8d9c5bc2fadeb425965974bdfb497577ebcc3b..53f9c1570ce62ddaa521d85d9ef64523e8ad0919 100644
--- a/arch/m68k/include/asm/dma.h
+++ b/arch/m68k/include/asm/dma.h
@@ -6,4 +6,5 @@
    bootmem allocator (but this should do it for this) */
 #define MAX_DMA_ADDRESS PAGE_OFFSET
 
+extern size_t dma_coldfire_base;
 #endif /* _M68K_DMA_H */
diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
index 16063783aa80c6ef200567543f98f011a2ac4dd2..bc66b012de79be842b55f3d82726a00c929416b9 100644
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
@@ -43,3 +43,13 @@ void arch_sync_dma_for_device(phys_addr_t handle, size_t size,
 		break;
 	}
 }
+
+#ifdef CONFIG_DMA_GLOBAL_POOL
+static int __init coldfire_dma_init(void)
+{
+	return dma_init_global_coherent(PFN_PHYS(PFN_DOWN(coldfire_dma_base)),
+					CONFIG_DMASIZE);
+}
+
+core_initcall(coldfire_dma_init);
+#endif
diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
index 9a6fa342e872e32ca9566ebfe247531c808f49d6..f6c560ea17a68ff6546b0683461b6b9ffb587db7 100644
--- a/arch/m68k/mm/mcfmmu.c
+++ b/arch/m68k/mm/mcfmmu.c
@@ -156,6 +156,8 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
 	return ret;
 }
 
+size_t coldfire_dma_base = _ramend - CONFIG_DMASIZE;
+
 void __init cf_bootmem_alloc(void)
 {
 	unsigned long memstart;
@@ -179,6 +181,9 @@ void __init cf_bootmem_alloc(void)
 	/* Reserve kernel text/data/bss */
 	memblock_reserve(_rambase, memstart - _rambase);
 
+	/* Reserve DMA */
+	memblock_reserve(coldfire_dma_base, CONFIG_DMASIZE);
+
 	m68k_virt_to_node_shift = fls(_ramend - 1) - 6;
 	module_fixup(NULL, __start_fixup, __stop_fixup);
 

-- 
2.39.5