Patchwork [v3,28/36] mtd: st_spi_fsm: Supply a busy wait for post-write status

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Submitter Lee Jones
Date Nov. 29, 2013, 12:19 p.m.
Message ID <1385727565-25794-29-git-send-email-lee.jones@linaro.org>
Download mbox | patch
Permalink /patch/295288/
State Superseded
Headers show

Comments

Lee Jones - Nov. 29, 2013, 12:19 p.m.
When we write data to the Serial Flash chip we'll wait a predetermined
period of time before giving up. During that period of time we poll the
status register until completion.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/mtd/devices/st_spi_fsm.c | 52 ++++++++++++++++++++++++++++++++++++++++
 drivers/mtd/devices/st_spi_fsm.h | 10 ++++++++
 2 files changed, 62 insertions(+)
Brian Norris - Dec. 11, 2013, 2:13 a.m.
On Fri, Nov 29, 2013 at 12:19:17PM +0000, Lee Jones wrote:
> --- a/drivers/mtd/devices/st_spi_fsm.c
> +++ b/drivers/mtd/devices/st_spi_fsm.c
> @@ -292,6 +308,42 @@ static int stfsm_enter_32bit_addr(struct stfsm *fsm, int enter)
>  	return 0;
>  }
>  
> +static uint8_t stfsm_wait_busy(struct stfsm *fsm)
> +{
> +	struct stfsm_seq *seq = &stfsm_seq_read_status_fifo;
> +	unsigned long deadline;
> +	uint32_t status;
> +
> +	/* Use RDRS1 */
> +	seq->seq_opc[0] = (SEQ_OPC_PADS_1 |
> +			   SEQ_OPC_CYCLES(8) |
> +			   SEQ_OPC_OPCODE(FLASH_CMD_RDSR));
> +
> +	/* Load read_status sequence */
> +	stfsm_load_seq(fsm, seq);
> +
> +	/* Repeat until busy bit is deasserted, or timeout */
> +	deadline = jiffies + FLASH_MAX_BUSY_WAIT;
> +	do {
> +		cond_resched();
> +
> +		stfsm_wait_seq(fsm);
> +
> +		stfsm_read_fifo(fsm, &status, 4);
> +
> +		if ((status & FLASH_STATUS_BUSY) == 0)
> +			return 0;
> +
> +		/* Restart */
> +		writel(seq->seq_cfg, fsm->base + SPI_FAST_SEQ_CFG);
> +
> +	} while (!time_after_eq(jiffies, deadline));

You have a timeout problem here, similar to the one I mentioned earlier,
except that in this one, your do/while at least ensures that you always
run the loop at least once... but still, what if "a long time" elapses
between stfsm_read_fifo() and checking time_after_eq()?

I think you want something like this after the while():

	stfsm_read_fifo(fsm, &status, 4);
	if ((status & FLASH_STATUS_BUSY) == 0)
		return 0;

> +	dev_err(fsm->dev, "timeout on wait_busy\n");
> +
> +	return -EIO;
> +}
> +
>  static int stfsm_wrvcr(struct stfsm *fsm, uint8_t data)
>  {
>  	struct stfsm_seq *seq = &stfsm_seq_wrvcr;

Brian

Patch

diff --git a/drivers/mtd/devices/st_spi_fsm.c b/drivers/mtd/devices/st_spi_fsm.c
index c08805f..d8fc97b 100644
--- a/drivers/mtd/devices/st_spi_fsm.c
+++ b/drivers/mtd/devices/st_spi_fsm.c
@@ -118,6 +118,22 @@  static struct stfsm_seq stfsm_seq_read_jedec = {
 		    SEQ_CFG_STARTSEQ),
 };
 
+static struct stfsm_seq stfsm_seq_read_status_fifo = {
+	.data_size = TRANSFER_SIZE(4),
+	.seq_opc[0] = (SEQ_OPC_PADS_1 |
+		       SEQ_OPC_CYCLES(8) |
+		       SEQ_OPC_OPCODE(FLASH_CMD_RDSR)),
+	.seq = {
+		STFSM_INST_CMD1,
+		STFSM_INST_DATA_READ,
+		STFSM_INST_STOP,
+	},
+	.seq_cfg = (SEQ_CFG_PADS_1 |
+		    SEQ_CFG_READNOTWRITE |
+		    SEQ_CFG_CSDEASSERT |
+		    SEQ_CFG_STARTSEQ),
+};
+
 static struct stfsm_seq stfsm_seq_erase_sector = {
 	/* 'addr_cfg' configured during initialisation */
 	.seq_opc = {
@@ -292,6 +308,42 @@  static int stfsm_enter_32bit_addr(struct stfsm *fsm, int enter)
 	return 0;
 }
 
+static uint8_t stfsm_wait_busy(struct stfsm *fsm)
+{
+	struct stfsm_seq *seq = &stfsm_seq_read_status_fifo;
+	unsigned long deadline;
+	uint32_t status;
+
+	/* Use RDRS1 */
+	seq->seq_opc[0] = (SEQ_OPC_PADS_1 |
+			   SEQ_OPC_CYCLES(8) |
+			   SEQ_OPC_OPCODE(FLASH_CMD_RDSR));
+
+	/* Load read_status sequence */
+	stfsm_load_seq(fsm, seq);
+
+	/* Repeat until busy bit is deasserted, or timeout */
+	deadline = jiffies + FLASH_MAX_BUSY_WAIT;
+	do {
+		cond_resched();
+
+		stfsm_wait_seq(fsm);
+
+		stfsm_read_fifo(fsm, &status, 4);
+
+		if ((status & FLASH_STATUS_BUSY) == 0)
+			return 0;
+
+		/* Restart */
+		writel(seq->seq_cfg, fsm->base + SPI_FAST_SEQ_CFG);
+
+	} while (!time_after_eq(jiffies, deadline));
+
+	dev_err(fsm->dev, "timeout on wait_busy\n");
+
+	return -EIO;
+}
+
 static int stfsm_wrvcr(struct stfsm *fsm, uint8_t data)
 {
 	struct stfsm_seq *seq = &stfsm_seq_wrvcr;
diff --git a/drivers/mtd/devices/st_spi_fsm.h b/drivers/mtd/devices/st_spi_fsm.h
index e168296..5143843 100644
--- a/drivers/mtd/devices/st_spi_fsm.h
+++ b/drivers/mtd/devices/st_spi_fsm.h
@@ -229,8 +229,18 @@ 
 #define FLASH_CMD_READ4_1_1_4	0x6c
 #define FLASH_CMD_READ4_1_4_4	0xec
 
+/* Status register */
+#define FLASH_STATUS_BUSY	0x01
+#define FLASH_STATUS_WEL	0x02
+#define FLASH_STATUS_BP0	0x04
+#define FLASH_STATUS_BP1	0x08
+#define FLASH_STATUS_BP2	0x10
+#define FLASH_STATUS_SRWP0	0x80
+#define FLASH_STATUS_TIMEOUT	0xff
+
 #define FLASH_PAGESIZE		256			/* In Bytes    */
 #define FLASH_PAGESIZE_32	FLASH_PAGESIZE / 4	/* In uint32_t */
+#define FLASH_MAX_BUSY_WAIT	(300 * HZ)	/* Maximum 'CHIPERASE' time */
 
 /*
  * Flags to tweak operation of default read/write/erase routines