[PATCH v2 0/2] mtd: rawnand: denali: clean-up unnecessary hook and device reset

[PATCH v2 0/2] mtd: rawnand: denali: clean-up unnecessary hook and device reset

[Masahiro Yamada]

I sent this series on September,
and Miquel replied this series was applied:
http://patchwork.ozlabs.org/patch/967242/

But, It turned out not applied.

I rebased it and resending now.


Masahiro Yamada (2):
  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(-)

-- 
2.7.4

[PATCH v2 1/2] mtd: rawnand: denali: remove ->dev_ready() hook

[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 <yamada.masahiro@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) {
-- 
2.7.4

[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 <yamada.masahiro@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;
 
-- 
2.7.4

Re: [PATCH v2 0/2] mtd: rawnand: denali: clean-up unnecessary hook and device reset

[Miquel Raynal]

Hi Masahiro,

Masahiro Yamada <yamada.masahiro@socionext.com> wrote on Wed, 28 Nov
2018 14:27:35 +0900:

> I sent this series on September,
> and Miquel replied this series was applied:
> http://patchwork.ozlabs.org/patch/967242/
> 
> But, It turned out not applied.
> 
> I rebased it and resending now.
> 
> 
> Masahiro Yamada (2):
>   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