Operation method of controller configured to control nonvolatile memory device and operation method of storage device

An operation method of a controller which is configured to control a nonvolatile memory device, the method comprising:

• receiving cell counting data associated with selected memory cells included in the nonvolatile memory device from the nonvolatile memory device;
• adjusting operation parameters of the nonvolatile memory device based on the cell counting data, wherein the adjusting of the operation parameters of the nonvolatile memory device based on the cell counting data includes:
• detecting a degradation state of the selected memory cells based on the cell counting data;
• and
• controlling the operation parameters based on the degradation state;
• performing a valley search operation for the selected memory cells based on the adjusted operation parameters;
• and
• performing a read operation for the selected memory cells based on a result of the valley search operation.

An operation method of a controller which is configured to control a nonvolatile memory device, the method comprising:

• receiving cell counting data associated with selected memory cells included in the nonvolatile memory device from the nonvolatile memory device;
• adjusting operation parameters of the nonvolatile memory device based on the cell counting data;
• performing a valley search operation for the selected memory cells based on the adjusted operation parameters;
• and
• performing a read operation for the selected memory cells based on a result of the valley search operation, wherein the performing of the read operation for the selected memory cells based on the result of the valley search operation includes:
• determining optimal read levels based on the result of the valley search operation;
• and
• performing the read operation for the selected memory cells by using the optimal read levels.