linux-kernel - Re: [PATCH 1/2] mtd: mtk-quadspi: add support for memory-mapped flash reading

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Date:   Thu, 7 Nov 2019 11:36:03 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Chuanhong Guo <gch981213@...il.com>,
        <linux-mtd@...ts.infradead.org>
CC:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mtd: mtk-quadspi: add support for memory-mapped flash
 reading

Hi,

On 06/11/19 7:37 PM, Chuanhong Guo wrote:
> PIO reading mode on this controller is ridiculously inefficient
> (one cmd+addr+dummy sequence reads only one byte)
> This patch adds support for reading from memory-mapped flash area
> which increases reading speed from 1MB/s to 5.6MB/s
> 
> Signed-off-by: Chuanhong Guo <gch981213@...il.com>
> ---
>  drivers/mtd/spi-nor/mtk-quadspi.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/mtk-quadspi.c b/drivers/mtd/spi-nor/mtk-quadspi.c
> index 34db01ab6cab..ba8b3be39896 100644
> --- a/drivers/mtd/spi-nor/mtk-quadspi.c
> +++ b/drivers/mtd/spi-nor/mtk-quadspi.c
> @@ -106,6 +106,7 @@ struct mtk_nor {
>  	struct spi_nor nor;
>  	struct device *dev;
>  	void __iomem *base;	/* nor flash base address */
> +	void __iomem *flash_base;
>  	struct clk *spi_clk;
>  	struct clk *nor_clk;
>  };
> @@ -272,6 +273,11 @@ static ssize_t mtk_nor_read(struct spi_nor *nor, loff_t from, size_t length,
>  	mtk_nor_set_read_mode(mtk_nor);
>  	mtk_nor_set_addr(mtk_nor, addr);
>  
> +	if (mtk_nor->flash_base) {
> +		memcpy_fromio(buffer, mtk_nor->flash_base + from, length);
> +		return length;
> +	}
> +

Don't you need to check if access is still within valid memory mapped
window?

>  	for (i = 0; i < length; i++) {
>  		ret = mtk_nor_execute_cmd(mtk_nor, MTK_NOR_PIO_READ_CMD);
>  		if (ret < 0)
> @@ -475,6 +481,11 @@ static int mtk_nor_drv_probe(struct platform_device *pdev)
>  	if (IS_ERR(mtk_nor->base))
>  		return PTR_ERR(mtk_nor->base);
>  
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +	mtk_nor->flash_base = devm_ioremap_resource(&pdev->dev, res);

There is a single API now: devm_platform_ioremap_resource().

> +	if (IS_ERR(mtk_nor->flash_base))
> +		mtk_nor->flash_base = NULL;
> +
>  	mtk_nor->spi_clk = devm_clk_get(&pdev->dev, "spi");
>  	if (IS_ERR(mtk_nor->spi_clk))
>  		return PTR_ERR(mtk_nor->spi_clk);
> 

-- 
Regards
Vignesh