linux-kernel - Re: [RESEND PATCH v9] mtd: spi-nor: add hisilicon spi-nor flash controller driver

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Date:	Fri, 8 Apr 2016 16:26:14 +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 2016/4/7 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!

Regards,
Jiancheng

>> 	} else {
>> 		/* read HIFMC_DMA_MAX_LEN bytes at a time */
>> 		for (i = 0; i < len; i += HIFMC_DMA_MAX_LEN) {
>> 			hisi_spi_nor_dma_transfer(nor, from + i, host->dma_buffer,
>> 				HIFMC_DMA_MAX_LEN, FMC_OP_READ);
>> 			memcpy(read_buf + i, host->buffer, HIFMC_DMA_MAX_LEN);
>> 		}
>> 		/* read remaining bytes */
>> 		i -= HIFMC_DMA_MAX_LEN;
>> 		hisi_spi_nor_dma_transfer(nor, from + i, host->dma_buffer,
>> 				len - i, FMC_OP_READ);
>> 		memcpy(read_buf + i, host->buffer, len - i);
>> 	}
>> 	*retlen = len;
>>
>> 	return 0;
>> }
>>
[...]
>> On 2016/4/4 14:44, Brian Norris wrote:
>>> Hi Jiancheng,
>>>
>>> Looking good. In addition to Marek's comments, I have just a few small
>>> comments. I'll post a small diff at the end, and a few inline comments.
>>>
> 
>