Re: [PATCH 2/3] mtd: rawnand: sunxi: Add DMA support for sun8i

[Maxime Ripard <maxime.ripard@bootlin.com>]

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On Thu, Apr 04, 2019 at 06:21:10PM +0200, Miquel Raynal wrote:
> Allwinner NAND controllers can make use of DMA to enhance the I/O
> throughput thanks to ECC pipelining. DMA handling with sun8i NAND IP
> is a bit different than with the older SoCs, hence the introduction of
> a new compatible to handle:
> * the differences between register offsets,
> * the burst length change from 4 to minimum 8,
> * drive SRAM accesses through the AHB bus instead of the MBUS.
>
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  drivers/mtd/nand/raw/sunxi_nand.c | 75 ++++++++++++++++++++++++++++---
>  1 file changed, 68 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
> index 4282bc477761..49cd5067adaa 100644
> --- a/drivers/mtd/nand/raw/sunxi_nand.c
> +++ b/drivers/mtd/nand/raw/sunxi_nand.c
> @@ -42,7 +42,8 @@
>  #define NFC_REG_CMD		0x0024
>  #define NFC_REG_RCMD_SET	0x0028
>  #define NFC_REG_WCMD_SET	0x002C
> -#define NFC_REG_IO_DATA		0x0030
> +#define NFC_REG_A10_IO_DATA	0x0030
> +#define NFC_REG_A33_IO_DATA	0x0300
>  #define NFC_REG_ECC_CTL		0x0034
>  #define NFC_REG_ECC_ST		0x0038
>  #define NFC_REG_DEBUG		0x003C
> @@ -200,6 +201,22 @@ static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
>  	return container_of(nand, struct sunxi_nand_chip, nand);
>  }
>
> +/*
> + * NAND Controller capabilities structure: stores NAND controller capabilities
> + * for distinction between compatible strings.
> + *
> + * @sram_through_ahb:	On A33, we choose to access the internal RAM through AHB
> + *                      instead of MBUS (less configuration). A10+ use the MBUS

What do you mean by A10+ ?

> + *                      but no extra configuration is needed.
> + * @reg_io_data:	I/O data register
> + * @dma_maxburst:	DMA maxburst
> + */
> +struct sunxi_nfc_caps {
> +	bool sram_through_ahb;
> +	unsigned int reg_io_data;
> +	unsigned int dma_maxburst;
> +};

Ideally, the introduction of that structure and the introduction of
the A33 support should be separate patches.

>  /**
>   * struct sunxi_nfc - stores sunxi NAND controller information
>   *
> @@ -228,6 +245,7 @@ struct sunxi_nfc {
>  	struct list_head chips;
>  	struct completion complete;
>  	struct dma_chan *dmac;
> +	const struct sunxi_nfc_caps *caps;
>  };
>
>  static inline struct sunxi_nfc *to_sunxi_nfc(struct nand_controller *ctrl)
> @@ -350,10 +368,29 @@ static int sunxi_nfc_dma_op_prepare(struct sunxi_nfc *nfc, const void *buf,
>  		goto err_unmap_buf;
>  	}
>
> -	writel(readl(nfc->regs + NFC_REG_CTL) | NFC_RAM_METHOD,
> -	       nfc->regs + NFC_REG_CTL);
> +	/*
> +	 * On A33, we suppose the "internal RAM" (p.12 of the user manual)

Which user manual? It certainly isn't the A33 user manual :)

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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