Messages in this thread Patch in this message | | | Subject | PATCH] dma_get_required_mask() | From | James Bottomley <> | Date | 28 Jun 2004 16:10:43 -0500 |
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This patch implements dma_get_required_mask() which may be used by drivers to probe the optimal DMA descriptor type they should be implementing on the platform.
I've also tested it this time with the sym_2 driver...making it chose the correct descriptors for the platform. (although I don't have a 64 bit platform with >4GB memory, so I only confirmed it selects the 32 bit descriptors all the time...)
It should be ready for inclusion.
James
===== Documentation/DMA-API.txt 1.7 vs edited ===== --- 1.7/Documentation/DMA-API.txt 2004-03-23 12:12:38 -06:00 +++ edited/Documentation/DMA-API.txt 2004-06-28 10:12:19 -05:00 @@ -162,6 +162,20 @@ Returns: 1 if successful and 0 if not +u64 +dma_get_required_mask(struct device *dev) + +After setting the mask with dma_set_mask(), this API returns the +actual mask (within that already set) that the platform actually +requires to operate efficiently. Usually this means the returned mask +is the minimum required to cover all of memory. Examining the +required mask gives drivers with variable descriptor sizes the +opportunity to use smaller descriptors as necessary. + +Requesting the required mask does not alter the current mask. If you +wish to take advantage of it, you should issue another dma_set_mask() +call to lower the mask again. + Part Id - Streaming DMA mappings -------------------------------- ===== include/linux/dma-mapping.h 1.3 vs edited ===== --- 1.3/include/linux/dma-mapping.h 2004-03-30 19:53:54 -06:00 +++ edited/include/linux/dma-mapping.h 2004-06-28 10:07:55 -05:00 @@ -19,6 +19,29 @@ #define dma_sync_single dma_sync_single_for_cpu #define dma_sync_sg dma_sync_sg_for_cpu +#ifndef ARCH_HAS_DMA_GET_REQUIRED_MASK +static inline u64 dma_get_required_mask(struct device *dev) +{ + extern unsigned long max_pfn; /* defined in bootmem.h but may + not be included */ + u32 low_totalram = ((max_pfn - 1) << PAGE_SHIFT); + u32 high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT)); + u64 mask; + + if (!high_totalram) { + /* convert to mask just covering totalram */ + low_totalram = (1 << (fls(low_totalram) - 1)); + low_totalram += low_totalram - 1; + mask = low_totalram; + } else { + high_totalram = (1 << (fls(high_totalram) - 1)); + high_totalram += high_totalram - 1; + mask = (((u64)high_totalram) << 32) + 0xffffffff; + } + return mask & *dev->dma_mask; +} +#endif + #endif
===== mm/bootmem.c 1.26 vs edited ===== --- 1.26/mm/bootmem.c 2004-06-27 02:19:26 -05:00 +++ edited/mm/bootmem.c 2004-06-28 11:12:00 -05:00 @@ -16,6 +16,7 @@ #include <linux/init.h> #include <linux/bootmem.h> #include <linux/mmzone.h> +#include <linux/module.h> #include <asm/dma.h> #include <asm/io.h> @@ -26,6 +27,10 @@ unsigned long max_low_pfn; unsigned long min_low_pfn; unsigned long max_pfn; + +EXPORT_SYMBOL(max_pfn); /* This is exported so + * dma_get_required_mask(), which uses + * it, can be an inline function */ /* return the number of _pages_ that will be allocated for the boot bitmap */ unsigned long __init bootmem_bootmap_pages (unsigned long pages) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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