Date: Mon, 27 Sep 2010 11:04:17 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Neel Natu <neelnatu@gmail.com> Subject: Re: PATCH: fix bogus error message "bus_dmamem_alloc failed to align memory properly" Message-ID: <201009271104.17478.jhb@freebsd.org> In-Reply-To: <AANLkTik3gtndjQWh22fzq8vr_QTRAUwPRoca-wkVEYY=@mail.gmail.com> References: <AANLkTik3gtndjQWh22fzq8vr_QTRAUwPRoca-wkVEYY=@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Friday, September 24, 2010 9:00:44 pm Neel Natu wrote:
> Hi,
>
> This patch fixes the bogus error message from bus_dmamem_alloc() about
> the buffer not being aligned properly.
>
> The problem is that the check is against a virtual address as opposed
> to the physical address. contigmalloc() makes guarantees about
> the alignment of physical addresses but not the virtual address
> mapping it.
>
> Any objections if I commit this patch?
Hmmm, I guess you are doing super-page alignment rather than sub-page
alignment? In general I thought the busdma code only handled sub-page
alignment and doesn't fully handle requests for super-page alignment.
For example, since it insists on walking individual pages at a time, if you
had an alignment setting of 4 pages and passed in a single, aligned 4-page
buffer, bus_dma would actually bounce the last 3 pages so that each individual
page is 4-page aligned. At least, I think that is what would happen.
For sub-page alignment, the virtual and physical address alignments should be
the same.
> best
> Neel
>
> Index: sys/powerpc/powerpc/busdma_machdep.c
> ===================================================================
> --- sys/powerpc/powerpc/busdma_machdep.c (revision 213113)
> +++ sys/powerpc/powerpc/busdma_machdep.c (working copy)
> @@ -529,7 +529,7 @@
> CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
> __func__, dmat, dmat->flags, ENOMEM);
> return (ENOMEM);
> - } else if ((uintptr_t)*vaddr & (dmat->alignment - 1)) {
> + } else if (vtophys(*vaddr) & (dmat->alignment - 1)) {
> printf("bus_dmamem_alloc failed to align memory properly.\n");
> }
> #ifdef NOTYET
> Index: sys/sparc64/sparc64/bus_machdep.c
> ===================================================================
> --- sys/sparc64/sparc64/bus_machdep.c (revision 213113)
> +++ sys/sparc64/sparc64/bus_machdep.c (working copy)
> @@ -652,7 +652,7 @@
> }
> if (*vaddr == NULL)
> return (ENOMEM);
> - if ((uintptr_t)*vaddr % dmat->dt_alignment)
> + if (vtophys(*vaddr) % dmat->dt_alignment)
> printf("%s: failed to align memory properly.\n", __func__);
> return (0);
> }
> Index: sys/ia64/ia64/busdma_machdep.c
> ===================================================================
> --- sys/ia64/ia64/busdma_machdep.c (revision 213113)
> +++ sys/ia64/ia64/busdma_machdep.c (working copy)
> @@ -455,7 +455,7 @@
> }
> if (*vaddr == NULL)
> return (ENOMEM);
> - else if ((uintptr_t)*vaddr & (dmat->alignment - 1))
> + else if (vtophys(*vaddr) & (dmat->alignment - 1))
> printf("bus_dmamem_alloc failed to align memory properly.\n");
> return (0);
> }
> Index: sys/i386/i386/busdma_machdep.c
> ===================================================================
> --- sys/i386/i386/busdma_machdep.c (revision 213113)
> +++ sys/i386/i386/busdma_machdep.c (working copy)
> @@ -540,7 +540,7 @@
> CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
> __func__, dmat, dmat->flags, ENOMEM);
> return (ENOMEM);
> - } else if ((uintptr_t)*vaddr & (dmat->alignment - 1)) {
> + } else if (vtophys(*vaddr) & (dmat->alignment - 1)) {
> printf("bus_dmamem_alloc failed to align memory properly.\n");
> }
> if (flags & BUS_DMA_NOCACHE)
> Index: sys/amd64/amd64/busdma_machdep.c
> ===================================================================
> --- sys/amd64/amd64/busdma_machdep.c (revision 213113)
> +++ sys/amd64/amd64/busdma_machdep.c (working copy)
> @@ -526,7 +526,7 @@
> CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
> __func__, dmat, dmat->flags, ENOMEM);
> return (ENOMEM);
> - } else if ((uintptr_t)*vaddr & (dmat->alignment - 1)) {
> + } else if (vtophys(*vaddr) & (dmat->alignment - 1)) {
> printf("bus_dmamem_alloc failed to align memory properly.\n");
> }
> if (flags & BUS_DMA_NOCACHE)
> _______________________________________________
> freebsd-hackers@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
>
--
John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201009271104.17478.jhb>