Re: [RFC PATCH 1/3] mm/cma: Move dma contiguous changes into a seperate config

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Hello,

On 6/24/2013 10:25 AM, Aneesh Kumar K.V wrote:
From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>

We want to use CMA for allocating hash page table and real mode area for
PPC64. Hence move DMA contiguous related changes into a seperate config
so that ppc64 can enable CMA without requiring DMA contiguous.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>

It's nice to see that CMA is gaining another client in mainline Linux kernel.
I also like the idea of adding CONFIG_DMA_CMA for DMA-mapping related CMA
use to let others to use alloc_contig_range() interface.

However I noticed that You have almost copied the whole drivers/base.c for
separate use with PPC64 KVM. Is this really necessary? I think it should be
possible to isolate some common code, which plays with contiguous region
management and use it for both alloc_contig_range() clients (dma-mapping and
ppc64 kvm).

---
  arch/arm/configs/omap2plus_defconfig  |  2 +-
  arch/arm/configs/tegra_defconfig      |  2 +-
  arch/arm/include/asm/dma-contiguous.h |  2 +-
  arch/arm/mm/dma-mapping.c             |  6 +++---
  drivers/base/Kconfig                  | 21 +++++----------------
  drivers/base/Makefile                 |  2 +-
  include/linux/dma-contiguous.h        |  2 +-
  mm/Kconfig                            | 20 ++++++++++++++++++++
  8 files changed, 33 insertions(+), 24 deletions(-)

diff --git a/arch/arm/configs/omap2plus_defconfig b/arch/arm/configs/omap2plus_defconfig
index abbe319..098268f 100644
--- a/arch/arm/configs/omap2plus_defconfig
+++ b/arch/arm/configs/omap2plus_defconfig
@@ -71,7 +71,7 @@ CONFIG_MAC80211=m
  CONFIG_MAC80211_RC_PID=y
  CONFIG_MAC80211_RC_DEFAULT_PID=y
  CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
-CONFIG_CMA=y
+CONFIG_DMA_CMA=y
  CONFIG_CONNECTOR=y
  CONFIG_DEVTMPFS=y
  CONFIG_DEVTMPFS_MOUNT=y
diff --git a/arch/arm/configs/tegra_defconfig b/arch/arm/configs/tegra_defconfig
index f7ba3161..34ae8f2 100644
--- a/arch/arm/configs/tegra_defconfig
+++ b/arch/arm/configs/tegra_defconfig
@@ -79,7 +79,7 @@ CONFIG_RFKILL_GPIO=y
  CONFIG_DEVTMPFS=y
  CONFIG_DEVTMPFS_MOUNT=y
  # CONFIG_FIRMWARE_IN_KERNEL is not set
-CONFIG_CMA=y
+CONFIG_DMA_CMA=y
  CONFIG_MTD=y
  CONFIG_MTD_CHAR=y
  CONFIG_MTD_M25P80=y
diff --git a/arch/arm/include/asm/dma-contiguous.h b/arch/arm/include/asm/dma-contiguous.h
index 3ed37b4..e072bb2 100644
--- a/arch/arm/include/asm/dma-contiguous.h
+++ b/arch/arm/include/asm/dma-contiguous.h
@@ -2,7 +2,7 @@
  #define ASMARM_DMA_CONTIGUOUS_H
#ifdef __KERNEL__
-#ifdef CONFIG_CMA
+#ifdef CONFIG_DMA_CMA
#include <linux/types.h>
  #include <asm-generic/dma-contiguous.h>
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index ef3e0f3..1fb40dc 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -358,7 +358,7 @@ static int __init atomic_pool_init(void)
  	if (!pages)
  		goto no_pages;
- if (IS_ENABLED(CONFIG_CMA))
+	if (IS_ENABLED(CONFIG_DMA_CMA))
  		ptr = __alloc_from_contiguous(NULL, pool->size, prot, &page,
  					      atomic_pool_init);
  	else
@@ -670,7 +670,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
  		addr = __alloc_simple_buffer(dev, size, gfp, &page);
  	else if (!(gfp & __GFP_WAIT))
  		addr = __alloc_from_pool(size, &page);
-	else if (!IS_ENABLED(CONFIG_CMA))
+	else if (!IS_ENABLED(CONFIG_DMA_CMA))
  		addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller);
  	else
  		addr = __alloc_from_contiguous(dev, size, prot, &page, caller);
@@ -759,7 +759,7 @@ static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
  		__dma_free_buffer(page, size);
  	} else if (__free_from_pool(cpu_addr, size)) {
  		return;
-	} else if (!IS_ENABLED(CONFIG_CMA)) {
+	} else if (!IS_ENABLED(CONFIG_DMA_CMA)) {
  		__dma_free_remap(cpu_addr, size);
  		__dma_free_buffer(page, size);
  	} else {
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 07abd9d..74b7c98 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -202,11 +202,10 @@ config DMA_SHARED_BUFFER
  	  APIs extension; the file's descriptor can then be passed on to other
  	  driver.
-config CMA
-	bool "Contiguous Memory Allocator"
-	depends on HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK
-	select MIGRATION
-	select MEMORY_ISOLATION
+config DMA_CMA
+	bool "DMA Contiguous Memory Allocator"
+	depends on HAVE_DMA_CONTIGUOUS
+	select CMA
  	help
  	  This enables the Contiguous Memory Allocator which allows drivers
  	  to allocate big physically-contiguous blocks of memory for use with
@@ -215,17 +214,7 @@ config CMA
  	  For more information see <include/linux/dma-contiguous.h>.
  	  If unsure, say "n".
-if CMA
-
-config CMA_DEBUG
-	bool "CMA debug messages (DEVELOPMENT)"
-	depends on DEBUG_KERNEL
-	help
-	  Turns on debug messages in CMA.  This produces KERN_DEBUG
-	  messages for every CMA call as well as various messages while
-	  processing calls such as dma_alloc_from_contiguous().
-	  This option does not affect warning and error messages.
-
+if  DMA_CMA
  comment "Default contiguous memory area size:"
config CMA_SIZE_MBYTES
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 4e22ce3..5d93bb5 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -6,7 +6,7 @@ obj-y			:= core.o bus.o dd.o syscore.o \
  			   attribute_container.o transport_class.o \
  			   topology.o
  obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
-obj-$(CONFIG_CMA) += dma-contiguous.o
+obj-$(CONFIG_DMA_CMA) += dma-contiguous.o
  obj-y			+= power/
  obj-$(CONFIG_HAS_DMA)	+= dma-mapping.o
  obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
index 01b5c84..00141d3 100644
--- a/include/linux/dma-contiguous.h
+++ b/include/linux/dma-contiguous.h
@@ -57,7 +57,7 @@ struct cma;
  struct page;
  struct device;
-#ifdef CONFIG_CMA
+#ifdef CONFIG_DMA_CMA
/*
   * There is always at least global CMA area and a few optional device
diff --git a/mm/Kconfig b/mm/Kconfig
index e742d06..b362369 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -477,3 +477,23 @@ config FRONTSWAP
  	  and swap data is stored as normal on the matching swap device.
If unsure, say Y to enable frontswap.
+
+config CMA
+	bool "Contiguous Memory Allocator"
+	depends on HAVE_MEMBLOCK
+	select MIGRATION
+	select MEMORY_ISOLATION
+	help
+	  This enables the Contiguous Memory Allocator which allows other
+	  subsystem to allocate big physically-contiguous blocks of memory
+
+	  If unsure, say "n".
+
+config CMA_DEBUG
+	bool "CMA debug messages (DEVELOPMENT)"
+	depends on DEBUG_KERNEL && CMA
+	help
+	  Turns on debug messages in CMA.  This produces KERN_DEBUG
+	  messages for every CMA call as well as various messages while
+	  processing calls such as dma_alloc_from_contiguous().
+	  This option does not affect warning and error messages.

Best regards
--
Marek Szyprowski
Samsung R&D Institute Poland


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