From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiancheng Xue Subject: Re: [RESEND PATCH v9] mtd: spi-nor: add hisilicon spi-nor flash controller driver Date: Mon, 11 Apr 2016 09:28:15 +0800 Message-ID: <570AFDAF.9050607@huawei.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5707821F.4020300-ynQEQJNshbs@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Marek Vasut , Brian Norris Cc: linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org, juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org, furquan-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, suwenping-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, yanhaifeng-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, raojun-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, xuejiancheng-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, ml.yang-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, gaofei-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, yanghongwei-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, zhangzhenxing-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org List-Id: devicetree@vger.kernel.org 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. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html