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Commit 8927ad39 authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Boris Brezillon
Browse files

mtd: nand: denali: remove meaningless pipeline read-ahead operation 



The pipeline read-ahead function of the Denali IP enables continuous
reading from the device; while data is being read out by a CPU, the
controller maintains additional commands for streaming data from the
device.  This will reduce the latency of the second page or later.

This feature is obviously no help for per-page accessors of Linux
NAND driver interface.

In the current implementation, the pipeline command is issued to
load a single page, then data are read out immediately.  The use of
the pipeline operation is not adding any advantage, but just adding
complexity to the code.  Remove.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
parent 8aabdf37

drivers/mtd/nand/denali.c

+3 −39
Original line number Diff line number Diff line
@@ -84,7 +84,6 @@ static inline struct denali_nand_info *mtd_to_denali(struct mtd_info *mtd) 
#define SPARE_ACCESS		0x41

#define MAIN_ACCESS		0x42

#define MAIN_SPARE_ACCESS	0x43

#define PIPELINE_ACCESS		0x2000



#define DENALI_READ	0

#define DENALI_WRITE	0x100
@@ -683,15 +682,7 @@ static int denali_send_pipeline_cmd(struct denali_nand_info *denali, 
				    int access_type, int op)

{

	int status = PASS;

	uint32_t page_count = 1;

	uint32_t addr, cmd, irq_status, irq_mask;



	if (op == DENALI_READ)

		irq_mask = INTR__LOAD_COMP;

	else if (op == DENALI_WRITE)

		irq_mask = 0;

	else

		BUG();

	uint32_t addr, cmd;



	setup_ecc_for_xfer(denali, ecc_en, transfer_spare);
@@ -714,35 +705,8 @@ static int denali_send_pipeline_cmd(struct denali_nand_info *denali, 
		cmd = MODE_10 | addr;

		index_addr(denali, cmd, access_type);



		/*

		 * page 33 of the NAND controller spec indicates we should not

		 * use the pipeline commands in Spare area only mode.

		 * So we don't.

		 */

		if (access_type == SPARE_ACCESS) {

		cmd = MODE_01 | addr;

		iowrite32(cmd, denali->flash_mem);

		} else {

			index_addr(denali, cmd,

					PIPELINE_ACCESS | op | page_count);



			/*

			 * wait for command to be accepted

			 * can always use status0 bit as the

			 * mask is identical for each bank.

			 */

			irq_status = wait_for_irq(denali, irq_mask);



			if (irq_status == 0) {

				dev_err(denali->dev,

					"cmd, page, addr on timeout (0x%x, 0x%x, 0x%x)\n",

					cmd, denali->page, addr);

				status = FAIL;

			} else {

				cmd = MODE_01 | addr;

				iowrite32(cmd, denali->flash_mem);

			}

		}

	}

	return status;

}