diff options
Diffstat (limited to 'target/linux/bcm27xx/patches-5.4/950-0437-mm-refresh-ZONE_DMA-and-ZONE_DMA32-comments-in-enum-.patch')
| -rw-r--r-- | target/linux/bcm27xx/patches-5.4/950-0437-mm-refresh-ZONE_DMA-and-ZONE_DMA32-comments-in-enum-.patch | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/target/linux/bcm27xx/patches-5.4/950-0437-mm-refresh-ZONE_DMA-and-ZONE_DMA32-comments-in-enum-.patch b/target/linux/bcm27xx/patches-5.4/950-0437-mm-refresh-ZONE_DMA-and-ZONE_DMA32-comments-in-enum-.patch new file mode 100644 index 0000000000..23811e0b6e --- /dev/null +++ b/target/linux/bcm27xx/patches-5.4/950-0437-mm-refresh-ZONE_DMA-and-ZONE_DMA32-comments-in-enum-.patch @@ -0,0 +1,84 @@ +From 1c108eaeae73a504ac1b2d882bc1fefb91eecf17 Mon Sep 17 00:00:00 2001 +From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> +Date: Wed, 11 Sep 2019 20:25:46 +0200 +Subject: [PATCH] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum + zone_type' + +commit 734f9246e791d8da278957b2c326d7709b2a97c0 upstream. + +These zones usage has evolved with time and the comments were outdated. +This joins both ZONE_DMA and ZONE_DMA32 explanation and gives up to date +examples on how they are used on different architectures. + +Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> +Reviewed-by: Christoph Hellwig <hch@lst.de> +Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> +Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> +--- + include/linux/mmzone.h | 45 ++++++++++++++++++++++++------------------ + 1 file changed, 26 insertions(+), 19 deletions(-) + +--- a/include/linux/mmzone.h ++++ b/include/linux/mmzone.h +@@ -358,33 +358,40 @@ struct per_cpu_nodestat { + #endif /* !__GENERATING_BOUNDS.H */ + + enum zone_type { +-#ifdef CONFIG_ZONE_DMA + /* +- * ZONE_DMA is used when there are devices that are not able +- * to do DMA to all of addressable memory (ZONE_NORMAL). Then we +- * carve out the portion of memory that is needed for these devices. +- * The range is arch specific. +- * +- * Some examples +- * +- * Architecture Limit +- * --------------------------- +- * parisc, ia64, sparc <4G +- * s390, powerpc <2G +- * arm Various +- * alpha Unlimited or 0-16MB. ++ * ZONE_DMA and ZONE_DMA32 are used when there are peripherals not able ++ * to DMA to all of the addressable memory (ZONE_NORMAL). ++ * On architectures where this area covers the whole 32 bit address ++ * space ZONE_DMA32 is used. ZONE_DMA is left for the ones with smaller ++ * DMA addressing constraints. This distinction is important as a 32bit ++ * DMA mask is assumed when ZONE_DMA32 is defined. Some 64-bit ++ * platforms may need both zones as they support peripherals with ++ * different DMA addressing limitations. ++ * ++ * Some examples: ++ * ++ * - i386 and x86_64 have a fixed 16M ZONE_DMA and ZONE_DMA32 for the ++ * rest of the lower 4G. ++ * ++ * - arm only uses ZONE_DMA, the size, up to 4G, may vary depending on ++ * the specific device. ++ * ++ * - arm64 has a fixed 1G ZONE_DMA and ZONE_DMA32 for the rest of the ++ * lower 4G. ++ * ++ * - powerpc only uses ZONE_DMA, the size, up to 2G, may vary ++ * depending on the specific device. + * +- * i386, x86_64 and multiple other arches +- * <16M. ++ * - s390 uses ZONE_DMA fixed to the lower 2G. ++ * ++ * - ia64 and riscv only use ZONE_DMA32. ++ * ++ * - parisc uses neither. + */ ++#ifdef CONFIG_ZONE_DMA + ZONE_DMA, + #endif + #ifdef CONFIG_ZONE_DMA32 +- /* +- * x86_64 needs two ZONE_DMAs because it supports devices that are +- * only able to do DMA to the lower 16M but also 32 bit devices that +- * can only do DMA areas below 4G. +- */ + ZONE_DMA32, + #endif + /* |