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Subject[PATCH v3 03/37] mtd: nand: denali: remove meaningless pipeline read-ahead operation
Date
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: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v3: None
Changes in v2:
- Newly added

drivers/mtd/nand/denali.c | 42 +++---------------------------------------
1 file changed, 3 insertions(+), 39 deletions(-)

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index 4e6d03d..65cf7cc 100644
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -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);
- }
- }
+ cmd = MODE_01 | addr;
+ iowrite32(cmd, denali->flash_mem);
}
return status;
}
--
2.7.4
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