RFC: Introduce explicit_erase capability in the Flash API to support memory devices that may not require erase

drivers/disk/flashdisk.c

@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2016 Intel Corporation.
- * Copyright (c) 2022-2023 Nordic Semiconductor ASA
+ * Copyright (c) 2022-2024 Nordic Semiconductor ASA
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -19,6 +19,17 @@
 #include <zephyr/logging/log.h>
 LOG_MODULE_REGISTER(flashdisk, CONFIG_FLASHDISK_LOG_LEVEL);
 
+#if IS_ENABLED(CONFIG_FLASH_HAS_EXPLICIT_ERASE) && \
+ IS_ENABLED(CONFIG_FLASH_HAS_NO_EXPLICIT_ERASE)
+#define DISK_ON_EXPLICIT_ERASE(fd) ((fd)->erase_required)
+#define DISK_EXPLICIT_ERASE_RUNTIME_CHECK
+#elif IS_ENABLED(CONFIG_FLASH_HAS_EXPLICIT_ERASE)
+#define DISK_ON_EXPLICIT_ERASE(fd) (true)
+#else
+/* Assumed IS_ENABLED(CONFIG_FLASH_HAS_NO_EXPLICIT_ERASE) */
+#define DISK_ON_EXPLICIT_ERASE(fd) (false)
+#endif
+
 struct flashdisk_data {
  struct disk_info info;
  struct k_mutex lock;
@@ -32,11 +43,21 @@ struct flashdisk_data {
  off_t cached_addr;
  bool cache_valid;
  bool cache_dirty;
+#if defined(DISK_EXPLICIT_ERASE_RUNTIME_CHECK)
+ bool erase_required;
+#endif
 };
 
 #define GET_SIZE_TO_BOUNDARY(start, block_size) \
  (block_size - (start & (block_size - 1)))
 
+/*
+ * The default block size is used for devices not requiring erase.
+ * It defaults to 512 as this is most widely used sector size
+ * on storage devices.
+ */
+#define DEFAULT_BLOCK_SIZE 512
+
 static int disk_flash_access_status(struct disk_info *disk)
 {
  LOG_DBG("status : %s", disk->dev ? "okay" : "no media");
@@ -53,14 +74,25 @@ static int flashdisk_init_runtime(struct flashdisk_data *ctx,
  int rc;
  struct flash_pages_info page;
  off_t offset;
+#if defined(DISK_EXPLICIT_ERASE_RUNTIME_CHECK)
+ const struct flash_parameters *params;
 
- rc = flash_get_page_info_by_offs(ctx->info.dev, ctx->offset, &page);
- if (rc < 0) {
- LOG_ERR("Error %d while getting page info", rc);
- return rc;
+ params = flash_get_parameters(ctx->info.dev);
+ ctx->erase_required = params->caps.explicit_erase;
+#endif
+
+ if (DISK_ON_EXPLICIT_ERASE(ctx)) {
+ rc = flash_get_page_info_by_offs(ctx->info.dev, ctx->offset, &page);
+ if (rc < 0) {
+ LOG_ERR("Error %d while getting page info", rc);
+ return rc;
+ }
+
+ ctx->page_size = page.size;
+ } else {
+ ctx->page_size = DEFAULT_BLOCK_SIZE;
  }
 
- ctx->page_size = page.size;
  LOG_INF("Initialize device %s", ctx->info.name);
  LOG_INF("offset %lx, sector size %zu, page size %zu, volume size %zu",
  (long)ctx->offset, ctx->sector_size, ctx->page_size, ctx->size);
@@ -71,7 +103,7 @@ static int flashdisk_init_runtime(struct flashdisk_data *ctx,
  return 0;
  }
 
- if (IS_ENABLED(CONFIG_FLASHDISK_VERIFY_PAGE_LAYOUT)) {
+ if (DISK_ON_EXPLICIT_ERASE(ctx)) {
  if (ctx->offset != page.start_offset) {
  LOG_ERR("Disk %s does not start at page boundary",
  ctx->info.name);
@@ -213,8 +245,10 @@ static int flashdisk_cache_commit(struct flashdisk_data *ctx)
  return 0;
  }
 
- if (flash_erase(ctx->info.dev, ctx->cached_addr, ctx->page_size) < 0) {
- return -EIO;
+ if (DISK_ON_EXPLICIT_ERASE(ctx)) {
+ if (flash_erase(ctx->info.dev, ctx->cached_addr, ctx->page_size) < 0) {
+ return -EIO;
+ }
  }
 
  /* write data to flash */

drivers/flash/CMakeLists.txt

@@ -1,5 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
+zephyr_library_sources(flash_util.c)
+
 zephyr_syscall_header_ifdef(
  CONFIG_FLASH_SIMULATOR
  ${ZEPHYR_BASE}/include/zephyr/drivers/flash/flash_simulator.h

drivers/flash/Kconfig

@@ -17,11 +17,62 @@ config FLASH_HAS_EX_OP
  This option is selected by drivers that support flash extended
  operations.
 
+config FLASH_HAS_EXPLICIT_ERASE
+ bool
+ help
+ Device has does not do erase-on-write (erase-on-program, auto-erase
+ on write) and requires explicit erase procedure to be programmed
+ with random value, in place where it has already been programmed with
+ some other value, as program can only change bits from erased-value
+ to the opposite.
+ All pure Flash devices are evolution of EEPROM where erase has
+ been separated from write, EEPROM has erase-on-write, giving
+ it advantage of higher write speeds at a cost of larger erase block.
+ Note that explicit-erase capability does not warrants that
+ write without erase is not allowed, taking the above restrictions,
+ it only states that write of a random information will require
+ erase.
+ Erase is usually performed in pages, as we have chosen to name
+ the unit in Zephyr, that may have different naming in device
+ specifications, like pages, sectors or blocks, and may vary
+ in size, depending how they are named by vendor.
+ This option should be selected by drivers that serve
+ devices with such characteristic and is used and may be
+ used by users to provide paths in code that only serve
+ such devices, and could be optimized-out by compiler in
+ case where there is no such device in a system.
+
+config FLASH_HAS_NO_EXPLICIT_ERASE
+ bool
+ help
+ Device does not require explicit erase before programming
+ a new random value at any location that has been previously
+ programmed with some other value.
+ Note that the device may have erase-on-write (auto-erase),
+ as for example in EEPROM devices, but may also have no erase
+ at all.
+ A device driver may still provide erase callback,
+ especially if it is able to perform erase to accelerate
+ further writes or is able to fill the area requested for
+ erase, with single value, faster than consecutive writes
+ that would be used to emulate erase.
+ This option should be selected by drivers that serve
+ devices with such characteristic and is used and may be
+ used by users to provide paths in code that only serve
+ such devices, and could be optimized-out by compiler in
+ case where there is no such device in a system.
+ This option should be selected for any device that
+ can change storage bits, by write, from any value to opposite
+ value at any time.
+
+if FLASH_HAS_EXPLICIT_ERASE
+
 config FLASH_HAS_PAGE_LAYOUT
  bool
  help
  This option is enabled when the SoC flash driver supports
  retrieving the layout of flash memory pages.
+endif
 
 config FLASH_JESD216
  bool
@@ -77,13 +128,30 @@ config FLASH_SHELL_BUFFER_SIZE
 
 endif # FLASH_SHELL
 
+config FLASH_FILL_BUFFER_SIZE
+ int "Buffer size of flash_fill funciton"
+ default 32
+ help
+ Size of a buffer used by flash_fill function to fill a device with
+ specific value; this buffer is allocated on stack.
+ The buffer is needed as most devices have write-block alignment
+ requirements that which imposes minimal size of data, which can
+ be written to a device, and alignment of write offset.
+ Even if device does not have such requirement, filling device by
+ single bytes is not efficient.
+ Value selected here should be multiply of the largest write-block-size
+ among all the memory devices used in system.
+
+if FLASH_HAS_PAGE_LAYOUT
+
 config FLASH_PAGE_LAYOUT
  bool "API for retrieving the layout of pages"
- depends on FLASH_HAS_PAGE_LAYOUT
- default y
+ default FLASH_HAS_PAGE_LAYOUT
  help
  Enables API for retrieving the layout of flash memory pages.
 
+endif
+
 config FLASH_EX_OP_ENABLED
  bool "API for extended flash operations"
  depends on FLASH_HAS_EX_OP

drivers/flash/Kconfig.ambiq

@@ -6,7 +6,7 @@ config FLASH_AMBIQ
  default y
  depends on DT_HAS_AMBIQ_FLASH_CONTROLLER_ENABLED
  select AMBIQ_HAL
- select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_NO_EXPLICIT_ERASE
  help
  Enables Ambiq flash driver on MRAM.

drivers/flash/Kconfig.andes

@@ -12,6 +12,7 @@ menuconfig FLASH_ANDES_QSPI
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_JESD216
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  depends on !SPI_NOR
  help
  Enable driver for Andes QSPI

drivers/flash/Kconfig.at45

@@ -7,6 +7,7 @@ menuconfig SPI_FLASH_AT45
  depends on DT_HAS_ATMEL_AT45_ENABLED
  select FLASH_HAS_DRIVER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
+ select FLASH_HAS_EXPLICIT_ERASE
  select SPI
  help
  This driver can handle several instances of AT45 family chips that

drivers/flash/Kconfig.b91

@@ -7,5 +7,6 @@ config SOC_FLASH_TELINK_B91
  depends on DT_HAS_TELINK_B91_FLASH_CONTROLLER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enables Telink B91 flash driver.

drivers/flash/Kconfig.cadence_nand

@@ -10,6 +10,7 @@ config FLASH_CDNS_NAND
  depends on DT_HAS_CDNS_NAND_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enable Cadence NAND support.
 

drivers/flash/Kconfig.cadence_qspi_nor

@@ -7,6 +7,7 @@ config FLASH_CAD_QSPI_NOR
  depends on DT_HAS_CDNS_QSPI_NOR_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enable Cadence QSPI-NOR support.
 

drivers/flash/Kconfig.cc13xx_cc26xx

@@ -7,6 +7,7 @@ config SOC_FLASH_CC13XX_CC26XX
  depends on DT_HAS_TI_CC13XX_CC26XX_FLASH_CONTROLLER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select MPU_ALLOW_FLASH_WRITE if ARM_MPU
  help
  Enables TI SimpleLink CC13xx/CC26xx flash controller driver.

drivers/flash/Kconfig.esp32

@@ -7,6 +7,7 @@ config SOC_FLASH_ESP32
  depends on DT_HAS_ESPRESSIF_ESP32_FLASH_CONTROLLER_ENABLED
  select FLASH_HAS_DRIVER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enable ESP32 internal flash driver.
 

drivers/flash/Kconfig.gd32

@@ -7,6 +7,7 @@ config SOC_FLASH_GD32
  depends on (GD32_NV_FLASH_V1 || GD32_NV_FLASH_V2 || GD32_NV_FLASH_V3)
  select FLASH_HAS_DRIVER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
+ select FLASH_HAS_EXPLICIT_ERASE
  select MPU_ALLOW_FLASH_WRITE if ARM_MPU
  help
  Enable the GigaDevice GD32 flash driver.

drivers/flash/Kconfig.gecko

@@ -10,6 +10,7 @@ config SOC_FLASH_GECKO
  select FLASH_HAS_DRIVER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select SOC_GECKO_MSC
+ select FLASH_HAS_EXPLICIT_ERASE
  select MPU_ALLOW_FLASH_WRITE if ARM_MPU
  help
  Enable Silicon Labs Gecko series internal flash driver.

drivers/flash/Kconfig.ifx_cat1

@@ -12,6 +12,7 @@ config FLASH_INFINEON_CAT1
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
  select USE_INFINEON_FLASH
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enable the Flash driver for Infineon CAT1 family.
 

drivers/flash/Kconfig.it8xxx2

@@ -10,6 +10,7 @@ config SOC_FLASH_ITE_IT8XXX2
  select SOC_IT8XXX2_USE_ILM
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select HAS_FLASH_LOAD_OFFSET
  help
  The flash driver includes support for read, write and

drivers/flash/Kconfig.lpc

@@ -8,6 +8,7 @@ config SOC_FLASH_LPC
  DT_HAS_NXP_IAP_FMC54_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enables the LPC IAP flash shim driver.
  WARNING: This driver will disable the system interrupts for

drivers/flash/Kconfig.mcux

@@ -11,6 +11,7 @@ config SOC_FLASH_MCUX
  DT_HAS_NXP_IAP_MSF1_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select MPU_ALLOW_FLASH_WRITE if ARM_MPU
  help
  Enables the MCUX flash shim driver.
@@ -41,6 +42,7 @@ config FLASH_MCUX_FLEXSPI_NOR
  depends on DT_HAS_NXP_IMX_FLEXSPI_NOR_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select FLASH_JESD216
  select MEMC
  select MEMC_MCUX_FLEXSPI
@@ -51,6 +53,7 @@ config FLASH_MCUX_FLEXSPI_MX25UM51345G
  depends on DT_HAS_NXP_IMX_FLEXSPI_MX25UM51345G_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select MEMC
  select MEMC_MCUX_FLEXSPI
 
@@ -60,6 +63,7 @@ config FLASH_MCUX_FLEXSPI_HYPERFLASH
  depends on DT_HAS_NXP_IMX_FLEXSPI_HYPERFLASH_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select MEMC
  select MEMC_MCUX_FLEXSPI
 

drivers/flash/Kconfig.nios2_qspi

@@ -6,5 +6,6 @@ config SOC_FLASH_NIOS2_QSPI
  depends on HAS_ALTERA_HAL
  depends on DT_HAS_ALTR_NIOS2_QSPI_NOR_ENABLED
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  help
  Enables the Nios-II QSPI flash driver.

drivers/flash/Kconfig.nor

@@ -1,11 +1,14 @@
 # Copyright (c) 2018 Savoir-Faire Linux.
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
 # SPDX-License-Identifier: Apache-2.0
 
 menuconfig SPI_NOR
  bool "SPI NOR Flash"
  default y
  depends on DT_HAS_JEDEC_SPI_NOR_ENABLED
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_JESD216
  select FLASH_HAS_EX_OP

drivers/flash/Kconfig.nordic_qspi_nor

@@ -6,6 +6,7 @@ menuconfig NORDIC_QSPI_NOR
  default y
  depends on DT_HAS_NORDIC_QSPI_NOR_ENABLED
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select NRFX_QSPI
  select FLASH_JESD216
  select PINCTRL

drivers/flash/Kconfig.npcx_fiu

@@ -18,6 +18,7 @@ config FLASH_NPCX_FIU_NOR
  depends on FLASH_NPCX_FIU_QSPI
  select FLASH_HAS_DRIVER_ENABLED
  select FLASH_HAS_PAGE_LAYOUT
+ select FLASH_HAS_EXPLICIT_ERASE
  select FLASH_JESD216
  select FLASH_HAS_EX_OP
  help

drivers/flash/Kconfig.nrf

@@ -17,6 +17,7 @@ menuconfig SOC_FLASH_NRF
  depends on !FLASH_NRF_FORCE_ALT
  select FLASH_HAS_PAGE_LAYOUT
  select FLASH_HAS_DRIVER_ENABLED
+ select FLASH_HAS_EXPLICIT_ERASE
  select NRFX_NVMC
  select MPU_ALLOW_FLASH_WRITE if ARM_MPU
  help

drivers/flash/Kconfig.nrf_mram

@@ -9,7 +9,7 @@ config SOC_FLASH_NRF_MRAM
  default y
  depends on DT_HAS_NORDIC_MRAM_ENABLED
  select FLASH_HAS_DRIVER_ENABLED
- select FLASH_HAS_PAGE_LAYOUT
+ select FLASH_HAS_NO_EXPLICIT_ERASE
  imply MPU_ALLOW_FLASH_WRITE if ARM_MPU
  help
  Enables Nordic Semiconductor flash driver for MRAM in direct write mode.