drivers: flash: mcux flexspi nor: copy data to RAM buffer on write

This feature prevents issues when trying to write data to the flash
device that is located on or addressed at the same flash device.

An example is the mcuboot logic that writes a magic number to
the secondary partition header.

Signed-off-by: Pieter De Gendt <[email protected]>

Author: pdgendt

drivers/flash/Kconfig.mcux

@@ -34,6 +34,15 @@ config FLASH_MCUX_FLEXSPI_NOR
 	select MEMC
 	select MEMC_MCUX_FLEXSPI
 
+config FLASH_MCUX_FLEXSPI_NOR_WRITE_BUFFER
+	bool "MCUX FlexSPI NOR write RAM buffer"
+	default y
+	depends on FLASH_MCUX_FLEXSPI_NOR
+	help
+	  Copy the data to a RAM buffer before writing it to the flash.
+	  This prevents faults when the data to write would be located on the
+	  flash itself.
+
 config FLASH_MCUX_FLEXSPI_XIP
 	bool "MCUX FlexSPI flash access with xip"
 	depends on MEMC_MCUX_FLEXSPI

drivers/flash/flash_mcux_flexspi_nor.c

@@ -19,6 +19,10 @@
 #define NOR_WRITE_SIZE	1
 #define NOR_ERASE_VALUE	0xff
 
+#ifdef CONFIG_FLASH_MCUX_FLEXSPI_NOR_WRITE_BUFFER
+static uint8_t nor_write_buf[SPI_NOR_PAGE_SIZE];
+#endif
+
 LOG_MODULE_REGISTER(flash_flexspi_nor, CONFIG_FLASH_LOG_LEVEL);
 
 enum {
@@ -346,8 +350,15 @@ static int flash_flexspi_nor_write(const struct device *dev, off_t offset,
 
 	while (len) {
 		i = MIN(SPI_NOR_PAGE_SIZE, len);
+#ifdef CONFIG_FLASH_MCUX_FLEXSPI_NOR_WRITE_BUFFER
+		memcpy(nor_write_buf, src, i);
+#endif
 		flash_flexspi_nor_write_enable(dev);
+#ifdef CONFIG_FLASH_MCUX_FLEXSPI_NOR_WRITE_BUFFER
+		flash_flexspi_nor_page_program(dev, offset, nor_write_buf, i);
+#else
 		flash_flexspi_nor_page_program(dev, offset, src, i);
+#endif
 		flash_flexspi_nor_wait_bus_busy(dev);
 		memc_flexspi_reset(data->controller);
 		src += i;