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doc: add flash suspend feature to iram usage doc

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Armando
2022-01-11 16:02:50 +08:00
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docs/en/api-guides/performance/ram-usage.rst
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@@ -137,26 +137,48 @@ The following options will reduce IRAM usage of some ESP-IDF features:
- Disabling :ref:`CONFIG_SPI_MASTER_ISR_IN_IRAM` prevents spi_master interrupts from being serviced while writing to flash, and may otherwise reduce spi_master performance, but will save some IRAM.
- Setting :ref:`CONFIG_HAL_DEFAULT_ASSERTION_LEVEL` to disable assertion for HAL component will save some IRAM especially for HAL code who calls `HAL_ASSERT` a lot and resides in IRAM.
.. only:: esp32c3
Flash Suspend Feature
^^^^^^^^^^^^^^^^^^^^^
When using ESP Flash APIs and other APIs based on the former (NVS, Partition APIs, etc.), the Cache will be disabled. During this period of time, any code executed must reside in internal RAM (see :ref:`concurrency-constraints-flash`). Hence, interrupt handlers that are not in internal RAM will not be executed.
To achieve this, ESP-IDF Drivers usually have the following two options:
- an option to place the driver's internal ISR handler in internal RAM
- an option to place some control functions in internal RAM.
User ISR callbacks (and involved variables) have to be in internal RAM if they are also used in interrupt contexts.
Placing additional code into IRAM will exacerbate the IRAM usage. For this reason, there is :ref:`CONFIG_SPI_FLASH_AUTO_SUSPEND`, which can alleviate the aforementioned kinds of IRAM usage. By enabling this feature, cache won't be disabled when ESP Flash and ESP-Flash-based APIs are used. Therefore, code and data in Flash can be executed or accessed normally, but with some minor delay. See :ref:`Flash Auto Suspend <auto-suspend>` for more details about this feature.
Regarding the flash suspend feature usage, and corresponding response time delay, please also see this example :example:`system/flash_suspend` .
.. only:: esp32
When compiling for ESP32 revisions older than ECO3 (:ref:`CONFIG_ESP32_REV_MIN`), PSRAM cache bug workaround (:ref:`CONFIG_SPIRAM_CACHE_WORKAROUND`) option is enabled, and the C library functions normally located in ROM are recompiled with the workaround and placed into IRAM instead. For most applications, it is safe to move many of the C library functions into Flash, reclaiming some IRAM. Corresponding options include:
Putting C Library in Flash
^^^^^^^^^^^^^^^^^^^^^^^^^^
.. list::
When compiling for ESP32 revisions older than ECO3 (:ref:`CONFIG_ESP32_REV_MIN`), PSRAM cache bug workaround (:ref:`CONFIG_SPIRAM_CACHE_WORKAROUND`) option is enabled, and the C library functions normally located in ROM are recompiled with the workaround and placed into IRAM instead. For most applications, it is safe to move many of the C library functions into Flash, reclaiming some IRAM. Corresponding options include:
- :ref:`CONFIG_SPIRAM_CACHE_LIBJMP_IN_IRAM`: affects the functions ``longjmp`` and ``setjump``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBMATH_IN_IRAM`: affects the functions ``abs``, ``div``, ``labs``, ``ldiv``, ``quorem``, ``fpclassify`` and ``nan``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBNUMPARSER_IN_IRAM`: affects the functions ``utoa``, ``itoa``, ``atoi``, ``atol``, ``strtol``, and ``strtoul``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBIO_IN_IRAM`: affects the functions ``wcrtomb``, ``fvwrite``, ``wbuf``, ``wsetup``, ``fputwc``, ``wctomb_r``, ``ungetc``, ``makebuf``, ``fflush``, ``refill``, and ``sccl``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBTIME_IN_IRAM`: affects the functions ``asctime``, ``asctime_r``, ``ctime``, ``ctime_r``, ``lcltime``, ``lcltime_r``, ``gmtime``, ``gmtime_r``, ``strftime``, ``mktime``, ``tzset_r``, ``tzset``, ``time``, ``gettzinfo``, ``systimes``, ``month_lengths``, ``timelocal``, ``tzvars``, ``tzlock``, ``tzcalc_limits``, and ``strptime``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBCHAR_IN_IRAM`: affects the functions ``ctype_``, ``toupper``, ``tolower``, ``toascii``, ``strupr``, ``bzero``, ``isalnum``, ``isalpha``, ``isascii``, ``isblank``, ``iscntrl``, ``isdigit``, ``isgraph``, ``islower``, ``isprint``, ``ispunct``, ``isspace``, and ``isupper``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBMEM_IN_IRAM`: affects the functions ``memccpy``, ``memchr``, ``memmove``, and ``memrchr``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBSTR_IN_IRAM`: affects the functions ``strcasecmp``, ``strcasestr``, ``strchr``, ``strcoll``, ``strcpy``, ``strcspn``, ``strdup``, ``strdup_r``, ``strlcat``, ``strlcpy``, ``strlen``, ``strlwr``, ``strncasecmp``, ``strncat``, ``strncmp``, ``strncpy``, ``strndup``, ``strndup_r``, ``strrchr``, ``strsep``, ``strspn``, ``strstr``, ``strtok_r, and ``strupr``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBRAND_IN_IRAM`: affects the functions ``srand``, ``rand``, and ``rand_r``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBENV_IN_IRAM`: affects the functions ``environ``, ``envlock``, and ``getenv_r``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBFILE_IN_IRAM`: affects the functions lock``, ``isatty``, ``fclose``, ``open``, ``close``, ``creat``, ``read``, ``rshift``, ``sbrk``, ``stdio``, ``syssbrk``, ``sysclose``, ``sysopen``, ``creat``, ``sysread``, ``syswrite``, ``impure``, ``fwalk``, and ``findfp``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBMISC_IN_IRAM`: affects the functions ``raise`` and ``system``.
.. list::
The exact amount of IRAM saved will depend on how much C library code is actually used by the application. In addition to these, the following options may be used to move more of the C library code into Flash, however note that this may result in reduced performance. Also take care to not use corresponding C library functions from interrupts which may be called while cache is disabled (allocated with :c:macro:`ESP_INTR_FLAG_IRAM` flag), refer to :ref:`iram-safe-interrupt-handlers` for more details. For these reasons, the functions ``itoa``, ``memcmp``, ``memcpy``, ``memset``, ``strcat``, ``strcmp``, and ``strlen`` are always put in IRAM.
- :ref:`CONFIG_SPIRAM_CACHE_LIBJMP_IN_IRAM`: affects the functions ``longjmp`` and ``setjump``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBMATH_IN_IRAM`: affects the functions ``abs``, ``div``, ``labs``, ``ldiv``, ``quorem``, ``fpclassify`` and ``nan``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBNUMPARSER_IN_IRAM`: affects the functions ``utoa``, ``itoa``, ``atoi``, ``atol``, ``strtol``, and ``strtoul``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBIO_IN_IRAM`: affects the functions ``wcrtomb``, ``fvwrite``, ``wbuf``, ``wsetup``, ``fputwc``, ``wctomb_r``, ``ungetc``, ``makebuf``, ``fflush``, ``refill``, and ``sccl``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBTIME_IN_IRAM`: affects the functions ``asctime``, ``asctime_r``, ``ctime``, ``ctime_r``, ``lcltime``, ``lcltime_r``, ``gmtime``, ``gmtime_r``, ``strftime``, ``mktime``, ``tzset_r``, ``tzset``, ``time``, ``gettzinfo``, ``systimes``, ``month_lengths``, ``timelocal``, ``tzvars``, ``tzlock``, ``tzcalc_limits``, and ``strptime``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBCHAR_IN_IRAM`: affects the functions ``ctype_``, ``toupper``, ``tolower``, ``toascii``, ``strupr``, ``bzero``, ``isalnum``, ``isalpha``, ``isascii``, ``isblank``, ``iscntrl``, ``isdigit``, ``isgraph``, ``islower``, ``isprint``, ``ispunct``, ``isspace``, and ``isupper``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBMEM_IN_IRAM`: affects the functions ``memccpy``, ``memchr``, ``memmove``, and ``memrchr``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBSTR_IN_IRAM`: affects the functions ``strcasecmp``, ``strcasestr``, ``strchr``, ``strcoll``, ``strcpy``, ``strcspn``, ``strdup``, ``strdup_r``, ``strlcat``, ``strlcpy``, ``strlen``, ``strlwr``, ``strncasecmp``, ``strncat``, ``strncmp``, ``strncpy``, ``strndup``, ``strndup_r``, ``strrchr``, ``strsep``, ``strspn``, ``strstr``, ``strtok_r, and ``strupr``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBRAND_IN_IRAM`: affects the functions ``srand``, ``rand``, and ``rand_r``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBENV_IN_IRAM`: affects the functions ``environ``, ``envlock``, and ``getenv_r``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBFILE_IN_IRAM`: affects the functions lock``, ``isatty``, ``fclose``, ``open``, ``close``, ``creat``, ``read``, ``rshift``, ``sbrk``, ``stdio``, ``syssbrk``, ``sysclose``, ``sysopen``, ``creat``, ``sysread``, ``syswrite``, ``impure``, ``fwalk``, and ``findfp``.
- :ref:`CONFIG_SPIRAM_CACHE_LIBMISC_IN_IRAM`: affects the functions ``raise`` and ``system``.
The exact amount of IRAM saved will depend on how much C library code is actually used by the application. In addition to these, the following options may be used to move more of the C library code into Flash, however note that this may result in reduced performance. Also take care to not use corresponding C library functions from interrupts which may be called while cache is disabled (allocated with :c:macro:`ESP_INTR_FLAG_IRAM` flag), refer to :ref:`iram-safe-interrupt-handlers` for more details. For these reasons, the functions ``itoa``, ``memcmp``, ``memcpy``, ``memset``, ``strcat``, ``strcmp``, and ``strlen`` are always put in IRAM.
.. note::