61 lines
2.4 KiB
ReStructuredText
61 lines
2.4 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 items 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, we need to make sure both CPUs
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are not running any code from flash for the duration of the flash operation.
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In a single-core setup this is easy: we disable interrupts/scheduler and do
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the flash operation. In the dual-core setup this is slightly more complicated.
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We need to make sure that the other CPU doesn't run any code from flash.
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When SPI flash API is called on CPU A (can be PRO or APP), we start
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spi_flash_op_block_func function on CPU B using esp_ipc_call API. This API
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wakes up high priority task on CPU B and tells it to execute given function,
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in this case spi_flash_op_block_func. This function disables cache on CPU B and
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signals that cache is disabled by setting s_flash_op_can_start flag.
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Then the task on CPU A disables cache as well, and proceeds to execute flash
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operation.
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While flash operation is running, interrupts can still run on CPUs A and B.
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We assume that all interrupt code is placed into RAM. Once interrupt allocation
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API is added, we should add a flag to request interrupt to be disabled for
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the duration of flash operations.
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Once flash operation is complete, function on CPU A sets another flag,
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s_flash_op_complete, to let the task on CPU B know that it can re-enable
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cache and release the CPU. Then the function on CPU A re-enables the cache on
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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 (:envvar:`CONFIG_FREERTOS_UNICORE` enabled), we simply
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disable both caches, no inter-CPU communication takes place.
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API Reference - SPI Flash
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-------------------------
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.. include:: /_build/inc/esp_spi_flash.inc
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API Reference - Partition Table
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-------------------------------
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.. include:: /_build/inc/esp_partition.inc
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API Reference - Flash Encrypt
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-----------------------------
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.. include:: /_build/inc/esp_flash_encrypt.inc
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