The spi-nor framework currently expects all Fast Read operations to use 8
dummy clock cycles. Especially some drivers like m25p80 can only support
multiple of 8 dummy clock cycles.
On Micron memories, the number of dummy clock cycles to be used by Fast
Read commands can be safely set to 8 by updating the Volatile
Configuration Register (VCR).
Also the XIP bit is set at the same time when updating the VCR so the
Continuous Read mode is disabled: this prevents us from entering it by
mistake.
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx>
---
drivers/mtd/spi-nor/spi-nor.c | 72 ++++++++++++++++++++++++++++++++++++++-----
include/linux/mtd/spi-nor.h | 2 ++
2 files changed, 67 insertions(+), 7 deletions(-)
diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index ef520048edae..2b1a26588ae6 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1314,6 +1314,53 @@ static int winbond_set_single_mode(struct spi_nor *nor)
return 0;
}
+static int micron_set_dummy_cycles(struct spi_nor *nor, u8 read_dummy)
+{
+ u8 vcr, val, mask;
+ int ret;
+
+ /* Set bit3 (XIP) to disable the Continuous Read mode */
+ mask = GENMASK(7, 4) | BIT(3);
+ val = ((read_dummy << 4) | BIT(3)) & mask;
+
+ /* Read the Volatile Configuration Register (VCR). */
+ ret = nor->read_reg(nor, SPINOR_OP_RD_VCR, &vcr, 1);
+ if (ret < 0) {
+ dev_err(nor->dev, "error while reading VCR register\n");
+ return ret;
+ }
+
+ /* Check whether we need to update the number of dummy cycles. */
+ if ((vcr & mask) == val) {
+ nor->read_dummy = read_dummy;
+ return 0;
+ }
+
+ /* Update the number of dummy into the VCR. */
+ write_enable(nor);
+ vcr = (vcr & ~mask) | val;
+ ret = nor->write_reg(nor, SPINOR_OP_WR_VCR, &vcr, 1);
+ if (ret < 0) {
+ dev_err(nor->dev, "error while writing VCR register\n");
+ return ret;
+ }
+
+ ret = spi_nor_wait_till_ready(nor);
+ if (ret)
+ return ret;
+
+ /* Read VCR and check it. */
+ ret = nor->read_reg(nor, SPINOR_OP_RD_VCR, &vcr, 1);
+ if (ret < 0 || (vcr & mask) != val) {
+ dev_err(nor->dev, "Micron VCR dummy cycles not updated\n");
+ return -EINVAL;
+ }
+
+ /* Save the number of dummy cycles to use with Fast Read commands */
+ nor->read_dummy = read_dummy;
+ return 0;
+}
+
static int micron_set_protocol(struct spi_nor *nor, u8 mask, u8 val,
enum spi_nor_protocol proto)
{
@@ -1398,12 +1445,15 @@ static int micron_set_quad_mode(struct spi_nor *nor)
/*
* Whatever the Quad mode is enabled or not, the
* Fast Read Quad Output 1-1-4 (0x6b) op code is supported.
+ * Force the number of dummy cycles to 8 and disable the Continuous Read
+ * mode to prevent some drivers from using it by mistake (m25p80).
+ * We can change these settings safely as we write into a volatile
+ * register.
*/
if (nor->read_proto != SNOR_PROTO_4_4_4)
nor->read_proto = SNOR_PROTO_1_1_4;
nor->read_opcode = SPINOR_OP_READ_1_1_4;
- nor->read_dummy = 8;
- return 0;
+ return micron_set_dummy_cycles(nor, 8);
}
static int micron_set_dual_mode(struct spi_nor *nor)
@@ -1428,12 +1478,15 @@ static int micron_set_dual_mode(struct spi_nor *nor)
/*
* Whatever the Dual mode is enabled or not, the
* Fast Read Dual Output 1-1-2 (0x3b) op code is supported.
+ * Force the number of dummy cycles to 8 and disable the Continuous Read
+ * mode to prevent some drivers from using it by mistake (m25p80).
+ * We can change these settings safely as we write into a volatile
+ * register.
*/
if (nor->read_proto != SNOR_PROTO_2_2_2)
nor->read_proto = SNOR_PROTO_1_1_2;
nor->read_opcode = SPINOR_OP_READ_1_1_2;
- nor->read_dummy = 8;
- return 0;
+ return micron_set_dummy_cycles(nor, 8);
}
static int micron_set_single_mode(struct spi_nor *nor)
@@ -1456,7 +1509,13 @@ static int micron_set_single_mode(struct spi_nor *nor)
nor->read_proto = SNOR_PROTO_1_1_1;
}
- /* Force the number of dummy cycles to 8 for Fast Read, 0 for Read. */
+ /*
+ * Force the number of dummy cycles to 8 for Fast Read, 0 for Read
+ * and disable the Continuous Read mode to prevent some drivers from
+ * using it by mistake (m25p80).
+ * We can change these settings safely as we write into a volatile
+ * register.
+ */
switch (nor->read_opcode) {
case SPINOR_OP_READ:
case SPINOR_OP_READ4:
@@ -1467,8 +1526,7 @@ static int micron_set_single_mode(struct spi_nor *nor)
read_dummy = 8;
break;
}
- nor->read_dummy = read_dummy;
- return 0;
+ return micron_set_dummy_cycles(nor, read_dummy);
}
static int spansion_set_quad_mode(struct spi_nor *nor)
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index d0a6f343a063..2dc0f8b429ca 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -86,6 +86,8 @@
/* Used for Micron flashes only. */
#define SPINOR_OP_MIO_RDID 0xaf /* Multiple I/O Read JEDEC ID */
+#define SPINOR_OP_RD_VCR 0x85 /* Read VCR register */
+#define SPINOR_OP_WR_VCR 0x81 /* Write VCR register */
#define SPINOR_OP_RD_EVCR 0x65 /* Read EVCR register */
#define SPINOR_OP_WD_EVCR 0x61 /* Write EVCR register */
--
1.8.2.2
--
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