linux-kernel - [PATCH v14 09/15] mtd: spi-nor: Introduce SNOR_F_IO_MODE_EN

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Date:   Thu, 1 Oct 2020 00:27:26 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC:     Pratyush Yadav <p.yadav@...com>, Sekhar Nori <nsekhar@...com>,
        Boris Brezillon <boris.brezillon@...labora.com>
Subject: [PATCH v14 09/15] mtd: spi-nor: Introduce SNOR_F_IO_MODE_EN_VOLATILE

From: Tudor Ambarus <tudor.ambarus@...rochip.com>

We don't want to enter a stateful mode, where a X-X-X I/O mode
is entered by setting a non-volatile bit, because in case of a
reset or a crash, once in the non-volatile mode, we may not be able
to recover in bootloaders and we may break the SPI NOR boot.

Forbid by default the I/O modes that are set via a non-volatile bit.

SPI_NOR_IO_MODE_EN_VOLATILE should be set just for the flashes that
don't define the optional SFDP SCCR Map, so that we don't pollute the
flash info flags.

Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
Signed-off-by: Pratyush Yadav <p.yadav@...com>
---
 drivers/mtd/spi-nor/core.c | 6 ++++++
 drivers/mtd/spi-nor/core.h | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 6b54a923002a..b42d59ab2724 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -3085,6 +3085,9 @@ static int spi_nor_octal_dtr_enable(struct spi_nor *nor, bool enable)
 	      nor->write_proto == SNOR_PROTO_8_8_8_DTR))
 		return 0;
 
+	if (!(nor->flags & SNOR_F_IO_MODE_EN_VOLATILE))
+		return 0;
+
 	ret = nor->params->octal_dtr_enable(nor, enable);
 	if (ret)
 		return ret;
@@ -3422,6 +3425,9 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 	if (info->flags & SPI_NOR_4B_OPCODES)
 		nor->flags |= SNOR_F_4B_OPCODES;
 
+	if (info->flags & SPI_NOR_IO_MODE_EN_VOLATILE)
+		nor->flags |= SNOR_F_IO_MODE_EN_VOLATILE;
+
 	ret = spi_nor_set_addr_width(nor);
 	if (ret)
 		return ret;
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 5cfe2db9ee13..105a4ddeb309 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -26,6 +26,7 @@ enum spi_nor_option_flags {
 	SNOR_F_HAS_SR_TB_BIT6	= BIT(11),
 	SNOR_F_HAS_4BIT_BP      = BIT(12),
 	SNOR_F_HAS_SR_BP3_BIT6  = BIT(13),
+	SNOR_F_IO_MODE_EN_VOLATILE = BIT(14),
 };
 
 struct spi_nor_read_command {
@@ -322,6 +323,11 @@ struct flash_info {
 					 */
 #define SPI_NOR_OCTAL_DTR_READ	BIT(19) /* Flash supports octal DTR Read. */
 #define SPI_NOR_OCTAL_DTR_PP	BIT(20) /* Flash supports Octal DTR Page Program */
+#define SPI_NOR_IO_MODE_EN_VOLATILE	BIT(21) /*
+						 * Flash enables the best
+						 * available I/O mode via a
+						 * volatile bit.
+						 */
 
 	/* Part specific fixup hooks. */
 	const struct spi_nor_fixups *fixups;
-- 
2.28.0