| Message ID | 1445986131-239566-2-git-send-email-borntraeger@de.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Christian, On Tue, Oct 27, 2015 at 11:48:48PM +0100, Christian Borntraeger wrote: > +static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page, > + unsigned long offset, size_t size, > + enum dma_data_direction dir, > + struct dma_attrs *attrs) > +{ > + return page_to_phys(page) + offset; > +} X86 also has its own version of these noop dma_ops, see arch/x86/kernel/pci-nommu.c. This one also checks the dma_mask and prints a warning if the physical address doesn't fit into the mask. I think this would make sense here too, and that we can also make x86 use the same generic noop-dma-ops your are introducing. Joerg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Am 28.10.2015 um 01:41 schrieb Joerg Roedel: > Hi Christian, > > On Tue, Oct 27, 2015 at 11:48:48PM +0100, Christian Borntraeger wrote: >> +static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page, >> + unsigned long offset, size_t size, >> + enum dma_data_direction dir, >> + struct dma_attrs *attrs) >> +{ >> + return page_to_phys(page) + offset; >> +} > > X86 also has its own version of these noop dma_ops, see > arch/x86/kernel/pci-nommu.c. This one also checks the dma_mask and > prints a warning if the physical address doesn't fit into the mask. > > I think this would make sense here too, and that we can also make x86 > use the same generic noop-dma-ops your are introducing. It not trivial without understanding the dma mask details. Do I read the x86 implementation right, that it limits the dma to 32 bit? Then we cannot collapse both implementations. Or maybe we can hide this in dma_capable. Dont know So I would prefer to keep it as is and let someone with x86 test environment do the unification. Christoph, I think you wanted to do that anyway, are you willing to do that? Christian -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Oct 30, 2015 at 01:55:56PM +0100, Christian Borntraeger wrote: > It not trivial without understanding the dma mask details. Do I read > the x86 implementation right, that it limits the dma to 32 bit? Then > we cannot collapse both implementations. Or maybe we can hide this in > dma_capable. Dont know No, DMA is not limited to 32bit on x86. Each device has its own dma_mask, and the requested address+size is checked against it. The DMA_BIT_MASK(32) check is only to there to print a warning when a 32bit capable device trys to access memory above 4GB. Joerg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index ac07ff0..7912f54 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -66,6 +66,8 @@ struct dma_map_ops { int is_phys; }; +extern struct dma_map_ops dma_noop_ops; + #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) #define DMA_MASK_NONE 0x0ULL diff --git a/lib/Makefile b/lib/Makefile index 13a7c6a..b04ba71 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ sha1.o md5.o irq_regs.o argv_split.o \ proportions.o flex_proportions.o ratelimit.o show_mem.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ - earlycpio.o seq_buf.o nmi_backtrace.o + earlycpio.o seq_buf.o nmi_backtrace.o dma-noop.o obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o lib-$(CONFIG_MMU) += ioremap.o diff --git a/lib/dma-noop.c b/lib/dma-noop.c new file mode 100644 index 0000000..3ce31302 --- /dev/null +++ b/lib/dma-noop.c @@ -0,0 +1,77 @@ +/* + * lib/dma-noop.c + * + * Stub DMA noop-ops + */ +#include <linux/export.h> +#include <linux/mm.h> +#include <linux/dma-mapping.h> +#include <linux/scatterlist.h> + +static void *dma_noop_alloc(struct device *dev, size_t size, + dma_addr_t *dma_handle, gfp_t gfp, + struct dma_attrs *attrs) +{ + void *ret; + + ret = (void *)__get_free_pages(gfp, get_order(size)); + if (ret) { + memset(ret, 0, size); + *dma_handle = virt_to_phys(ret); + } + return ret; +} + +static void dma_noop_free(struct device *dev, size_t size, + void *cpu_addr, dma_addr_t dma_addr, + struct dma_attrs *attrs) +{ + free_pages((unsigned long)cpu_addr, get_order(size)); +} + +static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page, + unsigned long offset, size_t size, + enum dma_data_direction dir, + struct dma_attrs *attrs) +{ + return page_to_phys(page) + offset; +} + +static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents, + enum dma_data_direction dir, struct dma_attrs *attrs) +{ + int i; + struct scatterlist *sg; + + for_each_sg(sgl, sg, nents, i) { + void *va; + + BUG_ON(!sg_page(sg)); + va = sg_virt(sg); + sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va); + sg_dma_len(sg) = sg->length; + } + + return nents; +} + +static int dma_noop_mapping_error(struct device *dev, dma_addr_t dma_addr) +{ + return 0; +} + +static int dma_noop_supported(struct device *dev, u64 mask) +{ + return 1; +} + +struct dma_map_ops dma_noop_ops = { + .alloc = dma_noop_alloc, + .free = dma_noop_free, + .map_page = dma_noop_map_page, + .map_sg = dma_noop_map_sg, + .mapping_error = dma_noop_mapping_error, + .dma_supported = dma_noop_supported, +}; + +EXPORT_SYMBOL(dma_noop_ops);
We are going to require dma_ops for several common drivers, even for systems that do have an identity mapping. Lets provide some minimal no-op dma_ops that can be used for that purpose. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> --- include/linux/dma-mapping.h | 2 ++ lib/Makefile | 2 +- lib/dma-noop.c | 77 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 80 insertions(+), 1 deletion(-) create mode 100644 lib/dma-noop.c