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

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Date:	Thu, 31 Mar 2016 15:24:45 +0800
From:	Jiancheng Xue <xuejiancheng@...wei.com>
To:	<robh+dt@...nel.org>, <dwmw2@...radead.org>,
	<computersforpeace@...il.com>,
	<boris.brezillon@...e-electrons.com>, <jteki@...nedev.com>,
	<ezequiel@...guardiasur.com.ar>, <juhosg@...nwrt.org>,
	<furquan@...gle.com>, <marek.vasut@...il.com>
CC:	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-mtd@...ts.infradead.org>, <yanhaifeng@...ilicon.com>,
	<yanghongwei@...ilicon.com>, <suwenping@...ilicon.com>,
	<raojun@...ilicon.com>, <ml.yang@...ilicon.com>,
	<gaofei@...ilicon.com>, <zhangzhenxing@...ilicon.com>,
	<xuejiancheng@...ilicon.com>
Subject: Re: [RESEND PATCH v9] mtd: spi-nor: add hisilicon spi-nor flash
 controller driver

Hi all,
    I'll highly appreciated any of your comments.

On 2016/3/26 16:11, Jiancheng Xue wrote:
> Add hisilicon spi-nor flash controller driver
> 
[...]
> +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;
> +	unsigned char *ptr = read_buf;
> +	size_t actual_len;
> +
> +	*retlen = 0;
> +	while (len > 0) {
> +		actual_len = (len >= HIFMC_DMA_MAX_LEN)
> +			? HIFMC_DMA_MAX_LEN : len;
> +		hisi_spi_nor_dma_transfer(nor, from, host->dma_buffer,
> +				actual_len, FMC_OP_READ);
> +		memcpy(ptr, host->buffer, actual_len);
> +		ptr += actual_len;
> +		from += actual_len;
> +		len -= actual_len;
> +		*retlen += actual_len;
> +	}
> +
> +	return 0;
> +}
For easy understanding, the read function will be changed like below:

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);
	} 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;
}

> +static void hisi_spi_nor_write(struct spi_nor *nor, loff_t to,
> +			size_t len, size_t *retlen, const u_char *write_buf)
> +{
> +	struct hifmc_priv *priv = nor->priv;
> +	struct hifmc_host *host = priv->host;
> +	const unsigned char *ptr = write_buf;
> +	size_t actual_len;
> +
> +	*retlen = 0;
> +	while (len > 0) {
> +		if (to & HIFMC_DMA_MASK)
> +			actual_len = (HIFMC_DMA_MAX_LEN - (to & HIFMC_DMA_MASK))
> +				>= len	? len
> +				: (HIFMC_DMA_MAX_LEN - (to & HIFMC_DMA_MASK));
> +		else
> +			actual_len = (len >= HIFMC_DMA_MAX_LEN)
> +				? HIFMC_DMA_MAX_LEN : len;
> +		memcpy(host->buffer, ptr, actual_len);
> +		hisi_spi_nor_dma_transfer(nor, to, host->dma_buffer, actual_len,
> +				FMC_OP_WRITE);
> +		to += actual_len;
> +		ptr += actual_len;
> +		len -= actual_len;
> +		*retlen += actual_len;
> +	}
> +}
> +
Because "len" passed from spi_nor_write is smaller than nor->page_size, and nor->page_size
is smaller than the length of host->dma_buffer. We can transfer "len" bytes data by
hisi_spi_nor_dma_transfer at one time. hisi_spi_nor_write can be simplified like below:

static void hisi_spi_nor_write(struct spi_nor *nor, loff_t to,
			size_t len, size_t *retlen, const u_char *write_buf)
{
	struct hifmc_priv *priv = nor->priv;
	struct hifmc_host *host = priv->host;

	/* len is smaller than dma buffer length*/
	memcpy(host->buffer, write_buf, len);
	hisi_spi_nor_dma_transfer(nor, to, host->dma_buffer, len,
					FMC_OP_WRITE);

	*retlen = len;
}

Regards,
Jiancheng