[PATCH v2 2/2] mtd: rawnand: denali: remove denali_reset_banks()

[Masahiro Yamada]

In nand_scan_ident(), the controller driver resets every NAND chip.
This is done by sending NAND_CMD_RESET. The Denali IP provides
another way to do the equivalent thing; if a bit is set in the
DEVICE_RESET register, the controller sends the RESET command to
the corresponding device. denali_reset_banks() uses it to reset
all devices beforehand.

This redundant reset sequence was needed to know the actual number
of chips before calling nand_scan_ident(); if DEVICE_RESET fails,
there is no chip in that chip select. Then, denali_reset_banks()
sets denali->max_banks to the number of detected chips.

As commit f486287d2372 ("mtd: nand: denali: fix bank reset function
to detect the number of chips") explained, nand_scan_ident() issued
Set Features (0xEF) command to all CS lines, some of which may not be
connected with a chip. Then, the driver would wait for R/B# response,
which never happens.

This problem was solved by commit 107b7d6a7ad4 ("mtd: rawnand: avoid
setting again the timings to mode 0 after a reset"). In the current
code, nand_setup_data_interface() is called from nand_scan_tail(),
which is invoked after the chip detection.

Now, we can really remove the redundant denali_nand_banks() by simply
passing the maximum number of chip selects supported by this IP
(typically 4 or 8) to nand_scan(). Let's leave all the chip detection
process to nand_scan_ident().

Signed-off-by: Masahiro Yamada <***@socionext.com>
---

Changes in v2: None

drivers/mtd/nand/raw/denali.c | 29 -----------------------------
1 file changed, 29 deletions(-)

diff --git a/drivers/mtd/nand/raw/denali.c b/drivers/mtd/nand/raw/denali.c
index ead6e60..2302010 100644
--- a/drivers/mtd/nand/raw/denali.c
+++ b/drivers/mtd/nand/raw/denali.c
@@ -1045,29 +1045,6 @@ static int denali_setup_data_interface(struct nand_chip *chip, int chipnr,
return 0;
}

-static void denali_reset_banks(struct denali_nand_info *denali)
-{
- u32 irq_status;
- int i;
-
- for (i = 0; i < denali->max_banks; i++) {
- denali->active_bank = i;
-
- denali_reset_irq(denali);
-
- iowrite32(DEVICE_RESET__BANK(i),
- denali->reg + DEVICE_RESET);
-
- irq_status = denali_wait_for_irq(denali,
- INTR__RST_COMP | INTR__INT_ACT | INTR__TIME_OUT);
- if (!(irq_status & INTR__INT_ACT))
- break;
- }
-
- dev_dbg(denali->dev, "%d chips connected\n", i);
- denali->max_banks = i;
-}
-
static void denali_hw_init(struct denali_nand_info *denali)
{
/*
@@ -1321,12 +1298,6 @@ int denali_init(struct denali_nand_info *denali)
}

denali_enable_irq(denali);
- denali_reset_banks(denali);
- if (!denali->max_banks) {
- /* Error out earlier if no chip is found for some reasons. */
- ret = -ENODEV;
- goto disable_irq;
- }

denali->active_bank = DENALI_INVALID_BANK;

[Masahiro Yamada]

The Denali NAND IP has no way to read out the current signal level
of the R/B# pin. Instead, denali_dev_ready() checks if the R/B#
transition has already happened. (The INTR__INT_ACT interrupt is
asserted at the rising edge of the R/B# pin.) It is not a correct
way to implement the ->dev_ready() hook.

In fact, it has a drawback; in the nand_scan_ident phase, the chip
detection iterates over maxchips until it fails to find a homogeneous
chip. For the last loop, nand_reset() fails if no chip is there.

If ->dev_ready hook exists, nand_command(_lp) calls nand_wait_ready()
after NAND_CMD_RESET. However, we know denali_dev_ready() never
returns 1 unless there exists a chip that toggles R/B# in that chip
select. Then, nand_wait_ready() just ends up with wasting 400 msec,
in the end, shows the "timeout while waiting for chip to become ready"
warning.

Let's remove the mis-implemented dev_ready hook, and fallback to
sending the NAND_CMD_STATUS and nand_wait_status_ready(), which
bails out more quickly.

Signed-off-by: Masahiro Yamada <***@socionext.com>
---

Changes in v2:
- Rebase

drivers/mtd/nand/raw/denali.c | 23 +----------------------
1 file changed, 1 insertion(+), 22 deletions(-)

diff --git a/drivers/mtd/nand/raw/denali.c b/drivers/mtd/nand/raw/denali.c
index 830ea24..ead6e60 100644
--- a/drivers/mtd/nand/raw/denali.c
+++ b/drivers/mtd/nand/raw/denali.c
@@ -204,18 +204,6 @@ static uint32_t denali_wait_for_irq(struct denali_nand_info *denali,
return denali->irq_status;
}

-static uint32_t denali_check_irq(struct denali_nand_info *denali)
-{
- unsigned long flags;
- uint32_t irq_status;
-
- spin_lock_irqsave(&denali->irq_lock, flags);
- irq_status = denali->irq_status;
- spin_unlock_irqrestore(&denali->irq_lock, flags);
-
- return irq_status;
-}
-
static void denali_read_buf(struct nand_chip *chip, uint8_t *buf, int len)
{
struct mtd_info *mtd = nand_to_mtd(chip);
@@ -288,8 +276,7 @@ static void denali_cmd_ctrl(struct nand_chip *chip, int dat, unsigned int ctrl)
return;

/*
- * Some commands are followed by chip->legacy.dev_ready or
- * chip->legacy.waitfunc.
+ * Some commands are followed by chip->legacy.waitfunc.
* irq_status must be cleared here to catch the R/B# interrupt later.
*/
if (ctrl & NAND_CTRL_CHANGE)
@@ -298,13 +285,6 @@ static void denali_cmd_ctrl(struct nand_chip *chip, int dat, unsigned int ctrl)
denali->host_write(denali, DENALI_BANK(denali) | type, dat);
}

-static int denali_dev_ready(struct nand_chip *chip)
-{
- struct denali_nand_info *denali = mtd_to_denali(nand_to_mtd(chip));
-
- return !!(denali_check_irq(denali) & INTR__INT_ACT);
-}
-
static int denali_check_erased_page(struct mtd_info *mtd,
struct nand_chip *chip, uint8_t *buf,
unsigned long uncor_ecc_flags,
@@ -1359,7 +1339,6 @@ int denali_init(struct denali_nand_info *denali)
chip->legacy.read_byte = denali_read_byte;
chip->legacy.write_byte = denali_write_byte;
chip->legacy.cmd_ctrl = denali_cmd_ctrl;
- chip->legacy.dev_ready = denali_dev_ready;
chip->legacy.waitfunc = denali_waitfunc;

if (features & FEATURES__INDEX_ADDR) {

[Miquel Raynal]

Hi Masahiro,

I sent this series on September,
http://patchwork.ozlabs.org/patch/967242/
But, It turned out not applied.
I rebased it and resending now.
mtd: rawnand: denali: remove ->dev_ready() hook
mtd: rawnand: denali: remove denali_reset_banks()
drivers/mtd/nand/raw/denali.c | 52 +------------------------------------------
1 file changed, 1 insertion(+), 51 deletions(-)

I don't know how I missed those. Sorry for that, they are now applied
on nand/next.


Thanks,
Miquèl