Re: [PATCH v3 05/17] mtd: spinand: Define ctrl_ops for non-page read/write op templates

[Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>]

On Sat, 1 Jan 2022 13:12:38 +0530
Apurva Nandan <a-nandan@xxxxxx> wrote:

> 'ctrl_ops' are op templates for non-page read/write operations,
> which are: reset, get_feature, set_feature, write_enable, block_erase,
> page_read and program_execute ops. The 'ctrl_ops' struct contains in it
> op templates for each of this op, as well as enum spinand_protocol
> denoting protocol of all these ops.
> 
> We require these new op templates because of deviation in standard
> SPINAND ops by manufacturers and also due to changes when there is a
> change in SPI protocol/mode. This prevents the core from live-patching
> and vendor-specific adjustments in ops.
> 
> Define 'ctrl_ops', add macros to initialize it and add it in
> spinand_device.
> 
> Signed-off-by: Apurva Nandan <a-nandan@xxxxxx>
> ---
>  include/linux/mtd/spinand.h | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
> index 439d8ce40e1d..e5df6220ec1e 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -356,6 +356,35 @@ struct spinand_op_variants {
>  			sizeof(struct spi_mem_op),			\
>  	}
>  
> +struct spinand_ctrl_ops {
> +	const struct {
> +		struct spi_mem_op reset;
> +		struct spi_mem_op get_feature;
> +		struct spi_mem_op set_feature;
> +		struct spi_mem_op write_enable;
> +		struct spi_mem_op block_erase;
> +		struct spi_mem_op page_read;
> +		struct spi_mem_op program_execute;
> +	} ops;
> +	const enum spinand_protocol protocol;

Do you really need that protocol field?

> +};
> +
> +#define SPINAND_CTRL_OPS(__protocol, __reset, __get_feature, __set_feature,	\
> +			 __write_enable, __block_erase, __page_read,		\
> +			 __program_execute)					\
> +	{									\
> +		.ops = {							\
> +			.reset = __reset,					\
> +			.get_feature = __get_feature,				\
> +			.set_feature = __set_feature,				\
> +			.write_enable = __write_enable,				\
> +			.block_erase = __block_erase,				\
> +			.page_read = __page_read,				\
> +			.program_execute = __program_execute,			\
> +		},								\
> +		.protocol = __protocol,						\
> +	}
> +
>  /**
>   * spinand_ecc_info - description of the on-die ECC implemented by a SPI NAND
>   *		      chip
> @@ -468,6 +497,8 @@ struct spinand_dirmap {
>   * @data_ops.read_cache: read cache op template
>   * @data_ops.write_cache: write cache op template
>   * @data_ops.update_cache: update cache op template
> + * @ctrl_ops: various SPI mem op templates for handling the flash device, i.e.
> + *	      non page-read/write ops.
>   * @select_target: select a specific target/die. Usually called before sending
>   *		   a command addressing a page or an eraseblock embedded in
>   *		   this die. Only required if your chip exposes several dies
> @@ -498,6 +529,8 @@ struct spinand_device {
>  		const struct spi_mem_op *update_cache;
>  	} data_ops;
>  
> +	const struct spinand_ctrl_ops *ctrl_ops;
> +

Okay, I had something slightly different in mind. First, I'd put all
templates in a struct:

struct spinand_op_templates {
	const struct spi_mem_op *read_cache;
	const struct spi_mem_op *write_cache;
	const struct spi_mem_op *update_cache;
	const struct spi_mem_op *reset;
	const struct spi_mem_op *get_feature;
	const struct spi_mem_op *set_feature;
	const struct spi_mem_op *write_enable;
	const struct spi_mem_op *block_erase;
	const struct spi_mem_op *page_load;
	const struct spi_mem_op *program_execute;
};

Then, at the spinand level, I'd define an array of templates:

enum spinand_protocol {
	SPINAND_1S_1S_1S,
	SPINAND_2S_2S_2S,
	SPINAND_4S_4S_4S,
	SPINAND_8S_8S_8S,
	SPINAND_8D_8D_8D,
	SPINAND_NUM_PROTOCOLS,
};

struct spinand_device {
	...
	enum spinand_protocol protocol;
	const struct spinand_op_templates *op_templates[SPINAND_NUM_PROTOCOLS];
	...
};

This way, you can easily pick the right set of operations based
on the protocol/mode you're in:

#define spinand_get_op_template(spinand, opname) \
	((spinand)->op_templates[(spinand)->protocol]->opname)

static int spinand_read_reg_op(struct spinand_device *spinand, u8 reg, u8 *val)
{
	struct spi_mem_op op = *spinand_get_op_template(spinand, get_feature);
	int ret;

	...
}