Re: [PATCH 10/11] nand: spi: Add generic SPI controller support

[Arnaud Mouiche <arnaud.mouiche@gmail.com>]

On 21/02/2017 09:00, Peter Pan wrote:
> This commit supports to use generic spi controller
> as SPI NAND controller.
>
> Signed-off-by: Peter Pan <peterpandong@micron.com>
> ---
>   drivers/mtd/nand/spi/Kconfig             |   2 +
>   drivers/mtd/nand/spi/Makefile            |   1 +
>   drivers/mtd/nand/spi/chips/Kconfig       |   5 +
>   drivers/mtd/nand/spi/chips/Makefile      |   1 +
>   drivers/mtd/nand/spi/chips/generic_spi.c | 269 +++++++++++++++++++++++++++++++
>   5 files changed, 278 insertions(+)
>   create mode 100644 drivers/mtd/nand/spi/chips/Kconfig
>   create mode 100644 drivers/mtd/nand/spi/chips/Makefile
>   create mode 100644 drivers/mtd/nand/spi/chips/generic_spi.c
[...]
> +/*
> + * generic_spi_nand_cmd_fn - to process a command to send to the SPI-NAND
> + * by generic SPI bus
> + * @chip: SPI-NAND device structure
> + * @cmd: command structure
> + * Description:
> + *   Set up the command buffer to send to the SPI controller.
> + *   The command buffer has to initialized to 0.
> + */
> +static int generic_spi_nand_cmd_fn(struct spi_nand_chip *chip,
> +				struct spi_nand_cmd *cmd)
> +{
> +	struct spi_nand_cmd_cfg *cmd_cfg = spi_nand_get_cmd_cfg(cmd->cmd);
> +	struct spi_message message;
> +	struct spi_transfer x[3];
> +	struct spi_device *spi = chip->priv;
> +	u8 buf[SPINAND_MAX_ADDR_LEN];
> +
> +	spi_message_init(&message);
> +	memset(x, 0, sizeof(x));
> +	x[0].len = 1;
> +	x[0].tx_nbits = 1;
> +	x[0].tx_buf = &cmd->cmd;
> +	spi_message_add_tail(&x[0], &message);
> +
> +	if (cmd_cfg->addr_bytes || cmd_cfg->dummy_bytes) {
> +		if (cmd_cfg->addr_bytes > cmd->n_addr) {
> +			memcpy(buf, cmd->addr, cmd->n_addr);
> +			memset(cmd->addr, 0, cmd->n_addr);
> +			memcpy(cmd->addr + cmd_cfg->addr_bytes - cmd->n_addr,
> +				buf, cmd->n_addr);
> +		}
> +		x[1].len = cmd_cfg->addr_bytes + cmd_cfg->dummy_bytes;
> +		x[1].tx_nbits = cmd_cfg->addr_bits;
> +		x[1].tx_buf = cmd->addr;
> +		spi_message_add_tail(&x[1], &message);
> +	}
> +	if (cmd->n_tx) {
> +		x[2].len = cmd->n_tx;
> +		x[2].tx_nbits = cmd_cfg->data_bits;
> +		x[2].tx_buf = cmd->tx_buf;
> +		spi_message_add_tail(&x[2], &message);
> +	} else if (cmd->n_rx) {
> +		x[2].len = cmd->n_rx;
> +		x[2].rx_nbits = cmd_cfg->data_bits;
> +		x[2].rx_buf = cmd->rx_buf;
> +		spi_message_add_tail(&x[2], &message);
> +	}
> +	return spi_sync(spi, &message);
> +}
> +
>
Just a spi speed consideration.
All the spi drivers I've work with are not very good for scatter/gather, 
and performance are dropping especially when you gather only 1 to 3 
bytes parts.
But we can manage this optimization later anyway, with proper speed 
figures, once the spinand framework will be merged.

Arnaud