+Russell Hi Jiancheng, On Tue, 12 Apr 2016 17:32:08 +0800 Jiancheng Xue <xuejiancheng@xxxxxxxxxx> wrote: > Hi Marek, > > On 2016/4/12 3:21, Marek Vasut wrote: > > On 04/11/2016 03:28 AM, Jiancheng Xue wrote: > >> 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? > > > > Take a look at drivers/spi/spi-mxs.c , look for "vmalloc" , does that > > solution help you in any way ? > > > No. I think this solution just processes the buffer within only one page. > I had referred to drivers/mtd/onenand/samsung.c and other files. > The corresponding code segment is as follows: > static int s5pc110_read_bufferram(struct mtd_info *mtd, int area, > unsigned char *buffer, int offset, size_t count) > { > void *buf = (void *) buffer; > dma_addr_t dma_src, dma_dst; > ... > /* Handle vmalloc address */ > if (buf >= high_memory) { > struct page *page; > > if (((size_t) buf & PAGE_MASK) != > ((size_t) (buf + count - 1) & PAGE_MASK)) > goto normal; > page = vmalloc_to_page(buf); > if (!page) > goto normal; > > ... > } else { > ... > } > > normal: > ... > memcpy(buffer, p, count); > > return 0; > } > I think memcpy in "normal" clause can't be removed. So I'd like to keep my original > implementation if it is also OK. What's your opinion? You might want to have a look at this series [1], and particularly at Russell's answers regarding DMA operations on non-lowmem memory. Best Regards, Boris [1]http://thread.gmane.org/gmane.linux.kernel.mm/149015 -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html