On Mon, 28 Sep 2020 16:23:34 +0200 Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote: > Some architectures need allocations to be done under a > specific address limit to allow DMA from I/O. > > We propose here a very simple page allocator to get > pages allocated under this specific limit. > > The DMA page allocator will only use part of the available memory > under the DMA address limit to let room for the standard allocator. > > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx> > --- > lib/alloc_dma_page.c | 57 ++++++++++++++++++++++++++++++++++++++++++++ > lib/alloc_dma_page.h | 24 +++++++++++++++++++ > lib/s390x/sclp.c | 2 ++ > s390x/Makefile | 1 + > 4 files changed, 84 insertions(+) > create mode 100644 lib/alloc_dma_page.c > create mode 100644 lib/alloc_dma_page.h (...) > diff --git a/lib/alloc_dma_page.h b/lib/alloc_dma_page.h > new file mode 100644 > index 0000000..85e1d2f > --- /dev/null > +++ b/lib/alloc_dma_page.h > @@ -0,0 +1,24 @@ > +/* > + * Page allocator for DMA definitions > + * > + * Copyright (c) IBM, Corp. 2020 > + * > + * Authors: > + * Pierre Morel <pmorel@xxxxxxxxxxxxx> > + * > + * This code is free software; you can redistribute it and/or modify it > + * under the terms of the GNU Library General Public License version 2. > + */ > +#ifndef _ALLOC_DMA_PAGE_H_ > +#define _ALLOC_DMA_PAGE_H_ > + > +#include <asm/page.h> > + > +void put_dma_page(void *dma_page); > +void *get_dma_page(void); > +phys_addr_t dma_page_alloc_init(phys_addr_t start_pfn, phys_addr_t nb_pages); > + > +#define DMA_MAX_PFN (0x80000000 >> PAGE_SHIFT) > +#define DMA_ALLOC_RATIO 8 Hm, shouldn't the architecture be able to decide where a dma page can be located? Or am I misunderstanding? > + > +#endif /* _ALLOC_DMA_PAGE_H_ */ (...)
