From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756355AbcDLJdV (ORCPT ); Tue, 12 Apr 2016 05:33:21 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:61852 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755795AbcDLJdT (ORCPT ); Tue, 12 Apr 2016 05:33:19 -0400 Subject: Re: [RESEND PATCH v9] mtd: spi-nor: add hisilicon spi-nor flash controller driver To: Marek Vasut , Brian Norris References: <1458979861-3619-1-git-send-email-xuejiancheng@huawei.com> <56F73BC9.5000300@gmail.com> <56F8F630.5050008@huawei.com> <20160404064418.GC13995@localhost> <5705C17F.9030904@huawei.com> <5705C5E2.6070206@denx.de> <57076B26.7030700@huawei.com> <5707821F.4020300@denx.de> <570AFDAF.9050607@huawei.com> <570BF933.2000607@denx.de> CC: , , , , , , , , , , , , , , , , From: Jiancheng Xue Message-ID: <570CC098.9070606@huawei.com> Date: Tue, 12 Apr 2016 17:32:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <570BF933.2000607@denx.de> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.217.211] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A0B0205.570CC09A.0271,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: e3f6da0932fb8164b0d68e58998a2281 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Regards, Jiancheng