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components/esp32,spi_flash: update some comments

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This commit is contained in:
Ivan Grokhotkov
2016-09-12 19:54:35 +08:00
parent 1b6022bd07
commit 23d5c7579b
3 changed files with 12 additions and 11 deletions
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18
components/spi_flash/esp_spi_flash.c
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@@ -36,15 +36,14 @@
the flash operation. In the dual-core setup this is slightly more complicated.
We need to make sure that the other CPU doesn't run any code from flash.
SPI flash driver starts two tasks (spi_flash_op_block_task), one pinned to
each CPU. Each task is associated with its own semaphore.
When SPI flash API is called on CPU A (can be PRO or APP), we wake up the task
on CPU B by "giving" the semaphore associated with it. Tasks resumes, disables
cache on CPU B, and acknowledges that it has taken the semaphore by setting
a flag (s_flash_op_can_start). Flash API function running on CPU A waits for
this flag to be set. Once the flag is set, it disables cache on CPU A and
starts flash operation.
When SPI flash API is called on CPU A (can be PRO or APP), we start
spi_flash_op_block_func function on CPU B using esp_ipc_call API. This API
wakes up high priority task on CPU B and tells it to execute given function,
in this case spi_flash_op_block_func. This function disables cache on CPU B and
signals that cache is disabled by setting s_flash_op_can_start flag.
Then the task on CPU A disables cache as well, and proceeds to execute flash
operation.
While flash operation is running, interrupts can still run on CPU B.
We assume that all interrupt code is placed into RAM.
@@ -52,8 +51,7 @@
Once flash operation is complete, 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. Task on CPU B returns
to suspended state by "taking" the semaphore.
CPU A as well and returns control to the calling code.
Additionally, all API functions are protected with a mutex (s_flash_op_mutex).