spi: Add spi_mem_calc_op_duration() helper

}

EXPORT_SYMBOL_GPL(spi_mem_adjust_op_freq);

/**

 * spi_mem_calc_op_duration() - Derives the theoretical length (in ns) of an

 *			        operation. This helps finding the best variant

 *			        among a list of possible choices.

 * @op: the operation to benchmark

 *

 * Some chips have per-op frequency limitations, PCBs usually have their own

 * limitations as well, and controllers can support dual, quad or even octal

 * modes, sometimes in DTR. All these combinations make it impossible to

 * statically list the best combination for all situations. If we want something

 * accurate, all these combinations should be rated (eg. with a time estimate)

 * and the best pick should be taken based on these calculations.

 *

 * Returns a ns estimate for the time this op would take.

 */

u64 spi_mem_calc_op_duration(struct spi_mem_op *op)

{

	u64 ncycles = 0;

	u32 ns_per_cycles;

	ns_per_cycles = 1000000000 / op->max_freq;

	ncycles += ((op->cmd.nbytes * 8) / op->cmd.buswidth) / (op->cmd.dtr ? 2 : 1);

	ncycles += ((op->addr.nbytes * 8) / op->addr.buswidth) / (op->addr.dtr ? 2 : 1);

	ncycles += ((op->dummy.nbytes * 8) / op->dummy.buswidth) / (op->dummy.dtr ? 2 : 1);

	ncycles += ((op->data.nbytes * 8) / op->data.buswidth) / (op->data.dtr ? 2 : 1);

	return ncycles * ns_per_cycles;

}

EXPORT_SYMBOL_GPL(spi_mem_calc_op_duration);

static ssize_t spi_mem_no_dirmap_read(struct spi_mem_dirmap_desc *desc,

				      u64 offs, size_t len, void *buf)

{

int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op);

void spi_mem_adjust_op_freq(struct spi_mem *mem, struct spi_mem_op *op);

u64 spi_mem_calc_op_duration(struct spi_mem_op *op);

bool spi_mem_supports_op(struct spi_mem *mem,

			 const struct spi_mem_op *op);