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Date: Thu, 9 Nov 2017 15:12:05 +0800 From: Greentime Hu <green.hu@...il.com> To: Arnd Bergmann <arnd@...db.de> Cc: Greentime <greentime@...estech.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Jason Cooper <jason@...edaemon.net>, Marc Zyngier <marc.zyngier@....com>, Rob Herring <robh+dt@...nel.org>, Networking <netdev@...r.kernel.org>, Vincent Chen <vincentc@...estech.com>, deanbo422@...il.com Subject: Re: [PATCH 13/31] nds32: DMA mapping API 2017-11-08 17:09 GMT+08:00 Arnd Bergmann <arnd@...db.de>: > On Wed, Nov 8, 2017 at 6:55 AM, Greentime Hu <green.hu@...il.com> wrote: > >> +static void consistent_sync(void *vaddr, size_t size, int direction) >> +{ >> + unsigned long start = (unsigned long)vaddr; >> + unsigned long end = start + size; >> + >> + switch (direction) { >> + case DMA_FROM_DEVICE: /* invalidate only */ >> + cpu_dma_inval_range(start, end); >> + break; >> + case DMA_TO_DEVICE: /* writeback only */ >> + cpu_dma_wb_range(start, end); >> + break; >> + case DMA_BIDIRECTIONAL: /* writeback and invalidate */ >> + cpu_dma_wbinval_range(start, end); >> + break; >> + default: >> + BUG(); >> + } >> +} > >> + >> +static void >> +nds32_dma_sync_single_for_cpu(struct device *dev, dma_addr_t handle, >> + size_t size, enum dma_data_direction dir) >> +{ >> + consistent_sync((void *)dma_to_virt(dev, handle), size, dir); >> +} >> + >> +static void >> +nds32_dma_sync_single_for_device(struct device *dev, dma_addr_t handle, >> + size_t size, enum dma_data_direction dir) >> +{ >> + consistent_sync((void *)dma_to_virt(dev, handle), size, dir); >> +} > > You do the same cache operations for _to_cpu and _to_device, which > usually works, > but is more expensive than you need. It's better to take the ownership into > account and only do what you need. > Thanks. Like this? static void nds32_dma_sync_single_for_cpu(struct device *dev, dma_addr_t handle, size_t size, enum dma_data_direction dir) { consistent_sync((void *)dma_to_virt(dev, handle), size, DMA_FROM_DEVICE); } static void nds32_dma_sync_single_for_device(struct device *dev, dma_addr_t handle, size_t size, enum dma_data_direction dir) { consistent_sync((void *)dma_to_virt(dev, handle), size, DMA_TO_DEVICE); }
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