Re: [PATCH v1] mtd: rawnand: meson: waiting w/o wired ready/busy pin

From: Liang Yang
Date: Tue Jun 06 2023 - 23:16:05 EST


Hi Arseniy,

On 2023/6/7 3:54, Arseniy Krasnov wrote:
[ EXTERNAL EMAIL ]

On 06.06.2023 22:51, Arseniy Krasnov wrote:
If there is no wired ready/busy pin, classic way to wait for command
completion is to use function 'nand_soft_waitrdy()'. Meson NAND has
special command which allows to wait for NAND_STATUS_READY bit without
reading status in a software loop (as 'nand_soft_waitrdy()' does). To
use it send this command along with NAND_CMD_STATUS, then wait for an
interrupt, and after interrupt send NAND_CMD_READ0. So this feature
allows to use interrupt driven waiting without wired ready/busy pin.

Suggested-by: Liang Yang <liang.yang@xxxxxxxxxxx>
Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
---
drivers/mtd/nand/raw/meson_nand.c | 58 ++++++++++++++++++++++++++++++-
1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
index 074e14225c06..f4c5309a9527 100644
--- a/drivers/mtd/nand/raw/meson_nand.c
+++ b/drivers/mtd/nand/raw/meson_nand.c
@@ -38,6 +38,7 @@
#define NFC_CMD_SCRAMBLER_DISABLE 0
#define NFC_CMD_SHORTMODE_DISABLE 0
#define NFC_CMD_RB_INT BIT(14)
+#define NFC_CMD_RB_INT_NO_PIN ((0xb << 10) | BIT(18) | BIT(16))

#define NFC_CMD_GET_SIZE(x) (((x) >> 22) & GENMASK(4, 0))

@@ -94,6 +95,7 @@

/* nand flash controller delay 3 ns */
#define NFC_DEFAULT_DELAY 3000
+#define NFC_NO_RB_PIN_DELAY 5

#define ROW_ADDER(page, index) (((page) >> (8 * (index))) & 0xff)
#define MAX_CYCLE_ADDRS 5
@@ -179,6 +181,7 @@ struct meson_nfc {
u32 info_bytes;

unsigned long assigned_cs;
+ bool no_rb_pin;
};

enum {
@@ -392,7 +395,41 @@ static void meson_nfc_set_data_oob(struct nand_chip *nand,
}
}

-static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
+static int meson_nfc_wait_no_rb_pin(struct meson_nfc *nfc, int timeout_ms)
+{
+ u32 cmd, cfg;
+
+ meson_nfc_cmd_idle(nfc, nfc->timing.twb);
+ meson_nfc_drain_cmd(nfc);
+ meson_nfc_wait_cmd_finish(nfc, CMD_FIFO_EMPTY_TIMEOUT);
+
+ cfg = readl(nfc->reg_base + NFC_REG_CFG);
+ cfg |= NFC_RB_IRQ_EN;
+ writel(cfg, nfc->reg_base + NFC_REG_CFG);
+
+ reinit_completion(&nfc->completion);
+ cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_STATUS;
+ writel(cmd, nfc->reg_base + NFC_REG_CMD);
+ meson_nfc_cmd_idle(nfc, NFC_NO_RB_PIN_DELAY);

^^^

+
+ /* use the max erase time as the maximum clock for waiting R/B */
+ cmd = NFC_CMD_RB | NFC_CMD_RB_INT_NO_PIN | nfc->timing.tbers_max;
+ writel(cmd, nfc->reg_base + NFC_REG_CMD);
+ meson_nfc_cmd_idle(nfc, NFC_NO_RB_PIN_DELAY);

^^^
Liang, I've implemented "new RB_INT" way instead of 'nand_soft_waitrdy()'. There were two numbers
2 and 5 in 'meson_nfc_cmd_idle()' as time argument (here and above). I've replaced both with
define of 5 == NFC_NO_RB_PIN_DELAY. Is it correct? 2 and 5 were from doc?

You can do like that. as i know, bigger has no impact.
yes, them come from the example code of the controller datasheet; but i think we can delete them also.


Thanks, Arseniy

+
+ if (!wait_for_completion_timeout(&nfc->completion,
+ msecs_to_jiffies(timeout_ms)))
+ return -ETIMEDOUT;
+
+ cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_READ0;
+ writel(cmd, nfc->reg_base + NFC_REG_CMD);
+ meson_nfc_drain_cmd(nfc);
+ meson_nfc_wait_cmd_finish(nfc, CMD_FIFO_EMPTY_TIMEOUT);
+
+ return 0;
+}
+
+static int meson_nfc_wait_rb_pin(struct meson_nfc *nfc, int timeout_ms)
{
u32 cmd, cfg;
int ret = 0;
@@ -420,6 +457,23 @@ static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
return ret;
}

+static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
+{
+ if (nfc->no_rb_pin) {
+ /* This mode is used when there is no wired R/B pin.
+ * It works like 'nand_soft_waitrdy()', but instead of
+ * polling NAND_CMD_STATUS bit in the software loop,
+ * it will wait for interrupt - controllers checks IO
+ * bus and when it detects NAND_CMD_STATUS on it, it
+ * raises interrupt. After interrupt, NAND_CMD_READ0 is
+ * sent as terminator of the ready waiting procedure.
+ */
+ return meson_nfc_wait_no_rb_pin(nfc, timeout_ms);
+ } else {
+ return meson_nfc_wait_rb_pin(nfc, timeout_ms);
+ }
+}
+
static void meson_nfc_set_user_byte(struct nand_chip *nand, u8 *oob_buf)
{
struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
@@ -1412,6 +1466,8 @@ static int meson_nfc_probe(struct platform_device *pdev)
return ret;
}

+ nfc->no_rb_pin = !of_property_read_bool(dev->of_node, "nand-rb");
+
writel(0, nfc->reg_base + NFC_REG_CFG);
ret = devm_request_irq(dev, irq, meson_nfc_irq, 0, dev_name(dev), nfc);
if (ret) {