51 lines
2.6 KiB
ReStructuredText
51 lines
2.6 KiB
ReStructuredText
.. include:: ../../../../components/spi_flash/README.rst
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See also
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--------
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- :doc:`Partition Table documentation <../../api-guides/partition-tables>`
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- :doc:`Over The Air Update (OTA) API <../system/ota>` provides high-level API for updating app firmware stored in flash.
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- :doc:`Non-Volatile Storage (NVS) API <nvs_flash>` provides a structured API for storing small pieces of data in SPI flash.
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.. _spi-flash-implementation-details:
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Implementation details
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----------------------
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In order to perform some flash operations, it is necessary to make sure that both CPUs are not running any code from flash for the duration of the flash operation:
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- In a single-core setup, the SDK does it by disabling interrupts/scheduler before performing the flash operation.
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- In a dual-core setup, this is slightly more complicated as the SDK needs to make sure that the other CPU is not running any code from flash.
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When SPI flash API is called on CPU A (can be PRO or APP), start the spi_flash_op_block_func function on CPU B using the esp_ipc_call API. This API wakes up a high priority task on CPU B and tells it to execute a given function, in this case, spi_flash_op_block_func. This function disables cache on CPU B and signals that the cache is disabled by setting the s_flash_op_can_start flag. Then the task on CPU A disables cache as well and proceeds to execute flash operation.
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While a flash operation is running, interrupts can still run on CPUs A and B. It is assumed that all interrupt code is placed into RAM. Once the interrupt allocation API is added, a flag should be added to request the interrupt to be disabled for the duration of a flash operations.
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Once the flash operation is complete, the function on CPU A sets another flag, s_flash_op_complete, to let the task on CPU B know that it can re-enable cache and release the CPU. Then the function on CPU A re-enables the cache on CPU A as well and returns control to the calling code.
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Additionally, all API functions are protected with a mutex (s_flash_op_mutex).
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In a single core environment (:ref:`CONFIG_FREERTOS_UNICORE` enabled), you need to disable both caches, so that no inter-CPU communication can take place.
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API Reference - SPI Flash
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-------------------------
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.. include-build-file:: inc/esp_flash_spi_init.inc
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.. include-build-file:: inc/esp_flash.inc
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.. include-build-file:: inc/spi_flash_types.inc
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.. _api-reference-partition-table:
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API Reference - Partition Table
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-------------------------------
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.. include-build-file:: inc/esp_partition.inc
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API Reference - Flash Encrypt
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-----------------------------
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.. include-build-file:: inc/esp_flash_encrypt.inc
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