[PATCH linux-next v2 09/14] mtd: spi-nor: configure the number of dummy clock cycles on Micron memories
From: Cyrille Pitchen <hidden>
Date: 2016-01-08 16:06:04
Also in:
linux-devicetree, lkml
Subsystem:
memory technology devices (mtd), spi nor subsystem, the rest · Maintainers:
Miquel Raynal, Richard Weinberger, Vignesh Raghavendra, Pratyush Yadav, Michael Walle, Linus Torvalds
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 <redacted> --- 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 353a0f6ac3fe..3f79619aea52 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c@@ -1341,6 +1341,53 @@ 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) {
@@ -1425,12 +1472,15 @@ 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)
@@ -1455,12 +1505,15 @@ 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)
@@ -1483,7 +1536,13 @@ 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:
@@ -1494,8 +1553,7 @@ 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