[PATCH v2] mtd: rawnand: meson: waiting w/o wired ready/busy pin

[Arseniy Krasnov]

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>
---
 Changelog:
 v1 -> v2:
  * Remove small delays from 'meson_nfc_wait_no_rb_pin()'. Both have no
    effect according Liang's message.
  * Type of 'no_rb_pin' is u32, the same as for 'nand-rb' property.
  * 'meson_nfc_wait_no_rb_pin()' doesn't send NAND_CMD_READ0 in case of
    page programming. Extra argument is added to 'meson_nfc_queue_rb()'
    to check that case.

 drivers/mtd/nand/raw/meson_nand.c | 74 +++++++++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
index 074e14225c06..ae404655b68c 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))
 
@@ -179,6 +180,7 @@ struct meson_nfc {
 	u32 info_bytes;
 
 	unsigned long assigned_cs;
+	u32 no_rb_pin;
 };
 
 enum {
@@ -392,7 +394,42 @@ 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,
+				    bool need_cmd_read0)
+{
+	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);
+
+	/* 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);
+
+	if (!wait_for_completion_timeout(&nfc->completion,
+					 msecs_to_jiffies(timeout_ms)))
+		return -ETIMEDOUT;
+
+	if (need_cmd_read0) {
+		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 +457,25 @@ 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,
+			      bool need_cmd_read0)
+{
+	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,
+						need_cmd_read0);
+	} 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);
@@ -623,7 +679,7 @@ static int meson_nfc_rw_cmd_prepare_and_execute(struct nand_chip *nand,
 	if (in) {
 		nfc->cmdfifo.rw.cmd1 = cs | NFC_CMD_CLE | NAND_CMD_READSTART;
 		writel(nfc->cmdfifo.rw.cmd1, nfc->reg_base + NFC_REG_CMD);
-		meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tR_max));
+		meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tR_max), true);
 	} else {
 		meson_nfc_cmd_idle(nfc, nfc->timing.tadl);
 	}
@@ -669,7 +725,7 @@ static int meson_nfc_write_page_sub(struct nand_chip *nand,
 
 	cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_PAGEPROG;
 	writel(cmd, nfc->reg_base + NFC_REG_CMD);
-	meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tPROG_max));
+	meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tPROG_max), false);
 
 	meson_nfc_dma_buffer_release(nand, data_len, info_len, DMA_TO_DEVICE);
 
@@ -952,7 +1008,8 @@ static int meson_nfc_exec_op(struct nand_chip *nand,
 			break;
 
 		case NAND_OP_WAITRDY_INSTR:
-			meson_nfc_queue_rb(nfc, instr->ctx.waitrdy.timeout_ms);
+			meson_nfc_queue_rb(nfc, instr->ctx.waitrdy.timeout_ms,
+					   true);
 			if (instr->delay_ns)
 				meson_nfc_cmd_idle(nfc, delay_idle);
 			break;
@@ -1412,6 +1469,15 @@ static int meson_nfc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = of_property_read_u32(dev->of_node, "nand-rb", &nfc->no_rb_pin);
+	if (ret) {
+		/* If property was not found, don't use rb pin. */
+		if (ret == -EINVAL)
+			nfc->no_rb_pin = 1;
+		else
+			return ret;
+	}
+
 	writel(0, nfc->reg_base + NFC_REG_CFG);
 	ret = devm_request_irq(dev, irq, meson_nfc_irq, 0, dev_name(dev), nfc);
 	if (ret) {
-- 
2.35.0