[PATCH] mtd: spi-nor: Add CHIP_ERASE optimization

[Marek Vasut]

Add support for CHIP_ERASE opcode 0xc7 . This is useful in case the
entire SPI NOR is supposed to be erase at once, as is it considerably
faster than 4k sector erase and even slightly faster than 64k block
erase. The spi_nor_erase_chip() implementation is adapted from Linux
6.1.y as of commit 7d54cb2c26dad ("Linux 6.1.14") . The chip erase is
only used in case the entire MTD device is being erased, and the chip
does support this functionality.

Timing figures from W25Q128JW:
16 MiB erase using 4kiB sector erase opcode 0x20 ... 107.5s
16 MiB erase using 64kiB block erase opcode 0xd8 ... 39.1s
16 MiB erase using chip erase opcode 0xc7 .......... 38.7s

Signed-off-by: Marek Vasut <marex at denx.de>
---
Cc: Jagan Teki <jagan at amarulasolutions.com>
Cc: Vignesh R <vigneshr at ti.com>
---
 drivers/mtd/spi/spi-nor-core.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 2c3116ee530..83d7fe44ee1 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -903,6 +903,30 @@ static int read_bar(struct spi_nor *nor, const struct flash_info *info)
 }
 #endif
 
+/**
+ * spi_nor_erase_chip() - Erase the entire flash memory.
+ * @nor:	pointer to 'struct spi_nor'.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_erase_chip(struct spi_nor *nor)
+{
+	struct spi_mem_op op =
+		SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_CHIP_ERASE, 0),
+			   SPI_MEM_OP_NO_ADDR,
+			   SPI_MEM_OP_NO_DUMMY,
+			   SPI_MEM_OP_NO_DATA);
+	int ret;
+
+	spi_nor_setup_op(nor, &op, nor->write_proto);
+
+	ret = spi_mem_exec_op(nor->spi, &op);
+	if (ret)
+		return ret;
+
+	return nor->mtd.size;
+}
+
 /*
  * Initiate the erasure of a single sector. Returns the number of bytes erased
  * on success, a negative error code on error.
@@ -974,7 +998,12 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 		if (ret < 0)
 			goto erase_err;
 
-		ret = spi_nor_erase_sector(nor, addr);
+		if (len == mtd->size &&
+		    !(nor->flags & SNOR_F_NO_OP_CHIP_ERASE)) {
+			ret = spi_nor_erase_chip(nor);
+		} else {
+			ret = spi_nor_erase_sector(nor, addr);
+		}
 		if (ret < 0)
 			goto erase_err;
 
-- 
2.39.2