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Date: Mon, 11 Apr 2016 09:28:15 +0800 From: Jiancheng Xue <xuejiancheng@...wei.com> To: Marek Vasut <marex@...x.de>, Brian Norris <computersforpeace@...il.com> CC: <linux-mtd@...ts.infradead.org>, <robh+dt@...nel.org>, <dwmw2@...radead.org>, <boris.brezillon@...e-electrons.com>, <juhosg@...nwrt.org>, <furquan@...gle.com>, <suwenping@...ilicon.com>, <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <yanhaifeng@...ilicon.com>, <raojun@...ilicon.com>, <xuejiancheng@...ilicon.com>, <ml.yang@...ilicon.com>, <gaofei@...ilicon.com>, <yanghongwei@...ilicon.com>, <zhangzhenxing@...ilicon.com> Subject: Re: [RESEND PATCH v9] mtd: spi-nor: add hisilicon spi-nor flash controller driver Hi, On 2016/4/8 18:04, Marek Vasut wrote: > On 04/08/2016 10:26 AM, Jiancheng Xue wrote: >> Hi, >> >> On 2016/4/7 10:28, Marek Vasut wrote: >>> On 04/07/2016 04:10 AM, Jiancheng Xue wrote: >>>> Hi Brian, >>>> Thank you very much for your comments. I'll fix these issues in next version. >>>> In addition, for easy understanding I'd like to rewrite hisi_spi_nor_write and >>>> hisi_spi_nor_read. Your comments on these modifications will be highly appreciated. >>> >>> Would you please stop top-posting ? It rubs some people the wrong way. >>> >> I feel very sorry about that. I have read the etiquette and won't make the same mistake again. >> >>>> static int hisi_spi_nor_read(struct spi_nor *nor, loff_t from, size_t len, >>>> size_t *retlen, u_char *read_buf) >>>> { >>>> struct hifmc_priv *priv = nor->priv; >>>> struct hifmc_host *host = priv->host; >>>> int i; >>>> >>>> /* read all bytes in only one time */ >>>> if (len <= HIFMC_DMA_MAX_LEN) { >>>> hisi_spi_nor_dma_transfer(nor, from, host->dma_buffer, >>>> len, FMC_OP_READ); >>>> memcpy(read_buf, host->buffer, len); >>> >>> Is all the ad-hoc memcpying necessary? I think you can use >>> dma_map_single() and co to obtain DMAble memory for your >>> controller's use and then you can probably get rid of most >>> of this stuff. >>> >> Considering read_buf >= high_mem case, I think it is also complicated to use dma_map_* >> and the DMA buffer allocated by the driver is still needed. But I am not sure about >> this. Please let me know if I am wrong. Thank you! > > Does your controller/DMA have a limitation where it's buffers must be in > the bottom 4GiB range ? The DMA framework should be able to take care of > such platform limitations. > When read_buf is allocated by vmalloc, the underlying physical memory may be not contiguous. In this case, dma_map_single can't be used directly. I think inner DMA buffer and memcpy are still needed. Am I right? Regards, Jiancheng.
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