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

[Apurva Nandan <a-nandan@ti.com>]

Hi Boris,

On 03/01/22 15:31, Boris Brezillon wrote:
> On Sat, 1 Jan 2022 13:12:38 +0530
> Apurva Nandan <a-nandan@ti.com> 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@ti.com>
>> ---
>>   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;
>
> 	...
> }

I find a couple of issues with this  method,

1. read_cache, write_cache, update_cache op templates don't fit well 
with the other non-data ops, as
these data ops are used to create a dirmap, and that can be done only 
once at probe time. Hence, there
is a different mechanism of selecting of data ops and non-data ops. 
Hence, this division in the op templates
struct as data_ops and ctrl_ops is required. Currently, the core only 
supports using a single protocol for
data ops, chosen at the time of probing.

2. If we use this single op_templates struct, I can't think of any good 
way to initialize these in the
manufacturers driver (winbond.c), refer to 17th patch in this series. 
Could you please suggest a macro
implementation also for winbond.c with the suggested op_templates struct.

Thanks,
Apurva Nandan