[PATCH v4 2/3] mtd: spinand: use the spi-mem poll status APIs

[patrice.chotard at foss.st.com]

From: Patrice Chotard <patrice.chotard at foss.st.com>

Make use of spi-mem poll status APIs to let advanced controllers
optimize wait operations.
This should also fix the high CPU usage for system that don't have
a dedicated STATUS poll block logic.

Signed-off-by: Patrice Chotard <patrice.chotard at foss.st.com>
Signed-off-by: Christophe Kerello <christophe.kerello at foss.st.com>
---
Changes in v4:
  - Update commit message.
  - Add comment which explains how delays has been calculated.
  - Rename SPINAND_STATUS_TIMEOUT_MS to SPINAND_WAITRDY_TIMEOUT_MS.

Changes in v3:
  - Add initial_delay_us and polling_delay_us parameters to spinand_wait()
  - Add SPINAND_READ/WRITE/ERASE/RESET_INITIAL_DELAY_US and
    SPINAND_READ/WRITE/ERASE/RESET_POLL_DELAY_US defines.

Changes in v2:
  - non-offload case is now managed by spi_mem_poll_status()

 drivers/mtd/nand/spi/core.c | 45 ++++++++++++++++++++++++++-----------
 include/linux/mtd/spinand.h | 22 ++++++++++++++++++
 2 files changed, 54 insertions(+), 13 deletions(-)

diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 17f63f95f4a2..3131fae0c715 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -473,20 +473,26 @@ static int spinand_erase_op(struct spinand_device *spinand,
 	return spi_mem_exec_op(spinand->spimem, &op);
 }
 
-static int spinand_wait(struct spinand_device *spinand, u8 *s)
+static int spinand_wait(struct spinand_device *spinand,
+			unsigned long initial_delay_us,
+			unsigned long poll_delay_us,
+			u8 *s)
 {
-	unsigned long timeo =  jiffies + msecs_to_jiffies(400);
+	struct spi_mem_op op = SPINAND_GET_FEATURE_OP(REG_STATUS,
+						      spinand->scratchbuf);
 	u8 status;
 	int ret;
 
-	do {
-		ret = spinand_read_status(spinand, &status);
-		if (ret)
-			return ret;
+	ret = spi_mem_poll_status(spinand->spimem, &op, STATUS_BUSY, 0,
+				  initial_delay_us,
+				  poll_delay_us,
+				  SPINAND_WAITRDY_TIMEOUT_MS);
+	if (ret)
+		return ret;
 
-		if (!(status & STATUS_BUSY))
-			goto out;
-	} while (time_before(jiffies, timeo));
+	status = *spinand->scratchbuf;
+	if (!(status & STATUS_BUSY))
+		goto out;
 
 	/*
 	 * Extra read, just in case the STATUS_READY bit has changed
@@ -526,7 +532,10 @@ static int spinand_reset_op(struct spinand_device *spinand)
 	if (ret)
 		return ret;
 
-	return spinand_wait(spinand, NULL);
+	return spinand_wait(spinand,
+			    SPINAND_RESET_INITIAL_DELAY_US,
+			    SPINAND_RESET_POLL_DELAY_US,
+			    NULL);
 }
 
 static int spinand_lock_block(struct spinand_device *spinand, u8 lock)
@@ -549,7 +558,10 @@ static int spinand_read_page(struct spinand_device *spinand,
 	if (ret)
 		return ret;
 
-	ret = spinand_wait(spinand, &status);
+	ret = spinand_wait(spinand,
+			   SPINAND_READ_INITIAL_DELAY_US,
+			   SPINAND_READ_POLL_DELAY_US,
+			   &status);
 	if (ret < 0)
 		return ret;
 
@@ -585,7 +597,10 @@ static int spinand_write_page(struct spinand_device *spinand,
 	if (ret)
 		return ret;
 
-	ret = spinand_wait(spinand, &status);
+	ret = spinand_wait(spinand,
+			   SPINAND_WRITE_INITIAL_DELAY_US,
+			   SPINAND_WRITE_POLL_DELAY_US,
+			   &status);
 	if (!ret && (status & STATUS_PROG_FAILED))
 		return -EIO;
 
@@ -768,7 +783,11 @@ static int spinand_erase(struct nand_device *nand, const struct nand_pos *pos)
 	if (ret)
 		return ret;
 
-	ret = spinand_wait(spinand, &status);
+	ret = spinand_wait(spinand,
+			   SPINAND_ERASE_INITIAL_DELAY_US,
+			   SPINAND_ERASE_POLL_DELAY_US,
+			   &status);
+
 	if (!ret && (status & STATUS_ERASE_FAILED))
 		ret = -EIO;
 
diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
index 6bb92f26833e..6988956b8492 100644
--- a/include/linux/mtd/spinand.h
+++ b/include/linux/mtd/spinand.h
@@ -170,6 +170,28 @@ struct spinand_op;
 struct spinand_device;
 
 #define SPINAND_MAX_ID_LEN	4
+/*
+ * For erase, write and read operation, we got the following timings :
+ * tBERS (erase) 1ms to 4ms
+ * tPROG 300us to 400us
+ * tREAD 25us to 100us
+ * In order to minimize latency, the min value is divided by 4 for the
+ * initial delay, and dividing by 20 for the poll delay.
+ * For reset, 5us/10us/500us if the device is respectively
+ * reading/programming/erasing when the RESET occurs. Since we always
+ * issue a RESET when the device is IDLE, 5us is selected for both initial
+ * and poll delay.
+ */
+#define SPINAND_READ_INITIAL_DELAY_US	6
+#define SPINAND_READ_POLL_DELAY_US	5
+#define SPINAND_RESET_INITIAL_DELAY_US	5
+#define SPINAND_RESET_POLL_DELAY_US	5
+#define SPINAND_WRITE_INITIAL_DELAY_US	75
+#define SPINAND_WRITE_POLL_DELAY_US	15
+#define SPINAND_ERASE_INITIAL_DELAY_US	250
+#define SPINAND_ERASE_POLL_DELAY_US	50
+
+#define SPINAND_WAITRDY_TIMEOUT_MS	400
 
 /**
  * struct spinand_id - SPI NAND id structure
-- 
2.17.1