From mboxrd@z Thu Jan  1 00:00:00 1970
From: Greentime Hu <green.hu@gmail.com>
Subject: Re: [PATCH v6 16/36] nds32: DMA mapping API
Date: Tue, 23 Jan 2018 16:23:27 +0800
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Cc: Greentime <greentime@andestech.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        David Howells <dhowells@redhat.com>,
        Will Deacon <will.deacon@arm.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        linux-serial@vger.kernel.org,
        Geert Uytterhoeven <geert.uytterhoeven@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
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        Guo Ren <ren_guo@c-sky.co
To: Arnd Bergmann <arnd@arndb.de>
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Hi, Arnd:

2018-01-18 18:26 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
> On Mon, Jan 15, 2018 at 6:53 AM, Greentime Hu <green.hu@gmail.com> wrote:
>> From: Greentime Hu <greentime@andestech.com>
>>
>> This patch adds support for the DMA mapping API. It uses dma_map_ops for
>> flexibility.
>>
>> Signed-off-by: Vincent Chen <vincentc@andestech.com>
>> Signed-off-by: Greentime Hu <greentime@andestech.com>
>
> I'm still unhappy about the way the cache flushes are done here as discussed
> before. It's not a show-stopped, but no Ack from me.

How about this implementation?

static void
nds32_dma_sync_single_for_cpu(struct device *dev, dma_addr_t handle,
                              size_t size, enum dma_data_direction dir)
{
        switch (direction) {
        case DMA_TO_DEVICE:     /* writeback only */
                break;
        case DMA_FROM_DEVICE:   /* invalidate only */
        case DMA_BIDIRECTIONAL: /* writeback and invalidate */
                cpu_dma_inval_range(start, end);
                break;
        default:
                BUG();
        }
}

static void
nds32_dma_sync_single_for_device(struct device *dev, dma_addr_t handle,
                                 size_t size, enum dma_data_direction dir)
{
        switch (direction) {
        case DMA_FROM_DEVICE:   /* invalidate only */
                break;
        case DMA_TO_DEVICE:     /* writeback only */
        case DMA_BIDIRECTIONAL: /* writeback and invalidate */
                cpu_dma_wb_range(start, end);
                break;
        default:
                BUG();
        }
}