From 9aa0e290796c2ee2142dac2c92dcbb1dc8a2d9f3 Mon Sep 17 00:00:00 2001
From: Ivan Grokhotkov <igrokhotkov@gmail.com>
Date: Wed, 11 Jan 2017 17:23:23 +0800
Subject: [PATCH] deep sleep: keep RTC_SLOW_MEM powered on if data is placed
 into RTC slow memory

---
 components/esp32/deep_sleep.c       | 18 ++++++++++++------
 components/esp32/include/esp_attr.h |  2 +-
 components/esp32/ld/esp32.common.ld |  2 ++
 docs/api/deep_sleep.rst             |  2 ++
 4 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/components/esp32/deep_sleep.c b/components/esp32/deep_sleep.c
index 774fd4ce7a..3eef7ca29d 100644
--- a/components/esp32/deep_sleep.c
+++ b/components/esp32/deep_sleep.c
@@ -302,12 +302,18 @@ static uint32_t get_power_down_flags()
 {
     // Where needed, convert AUTO options to ON. Later interpret AUTO as OFF.
 
-    // RTC_SLOW_MEM is needed only for the ULP.
-    // If RTC_SLOW_MEM is Auto, and ULP wakeup isn't enabled, power down RTC_SLOW_MEM.
-    if (s_config.pd_options[ESP_PD_DOMAIN_RTC_SLOW_MEM] == ESP_PD_OPTION_AUTO) {
-        if (s_config.wakeup_triggers & RTC_SAR_TRIG_EN) {
-            s_config.pd_options[ESP_PD_DOMAIN_RTC_SLOW_MEM] = ESP_PD_OPTION_ON;
-        }
+    // RTC_SLOW_MEM is needed for the ULP, so keep RTC_SLOW_MEM powered up if ULP
+    // is used and RTC_SLOW_MEM is Auto.
+    // If there is any data placed into .rtc.data or .rtc.bss segments, and
+    // RTC_SLOW_MEM is Auto, keep it powered up as well.
+
+    // These labels are defined in the linker script:
+    extern int _rtc_data_start, _rtc_data_end, _rtc_bss_start, _rtc_bss_end;
+
+    if (s_config.pd_options[ESP_PD_DOMAIN_RTC_SLOW_MEM] == ESP_PD_OPTION_AUTO ||
+            &_rtc_data_end > &_rtc_data_start ||
+            &_rtc_bss_end > &_rtc_bss_start) {
+        s_config.pd_options[ESP_PD_DOMAIN_RTC_SLOW_MEM] = ESP_PD_OPTION_ON;
     }
 
     // RTC_FAST_MEM is needed for deep sleep stub.
diff --git a/components/esp32/include/esp_attr.h b/components/esp32/include/esp_attr.h
index 7ef2920d98..911201aace 100644
--- a/components/esp32/include/esp_attr.h
+++ b/components/esp32/include/esp_attr.h
@@ -26,7 +26,7 @@
 // Forces data into DRAM instead of flash
 #define DRAM_ATTR __attribute__((section(".dram1")))
 
-// Forces a string into DRAM instrad of flash
+// Forces a string into DRAM instead of flash
 // Use as ets_printf(DRAM_STR("Hello world!\n"));
 #define DRAM_STR(str) (__extension__({static const DRAM_ATTR char __c[] = (str); (const char *)&__c;}))
 
diff --git a/components/esp32/ld/esp32.common.ld b/components/esp32/ld/esp32.common.ld
index 833eb90969..8cc3b5b22e 100644
--- a/components/esp32/ld/esp32.common.ld
+++ b/components/esp32/ld/esp32.common.ld
@@ -19,9 +19,11 @@ SECTIONS
   */
   .rtc.data :
   {
+    _rtc_data_start = ABSOLUTE(.);
     *(.rtc.data)
     *(.rtc.rodata)
     *rtc_wake_stub*.o(.data .rodata .data.* .rodata.* .bss .bss.*)
+    _rtc_data_end = ABSOLUTE(.);
   } > rtc_slow_seg
 
   /* RTC bss, from any source file named rtc_wake_stub*.c */
diff --git a/docs/api/deep_sleep.rst b/docs/api/deep_sleep.rst
index 3a458fb4a8..9e6642fd90 100644
--- a/docs/api/deep_sleep.rst
+++ b/docs/api/deep_sleep.rst
@@ -73,6 +73,8 @@ By default, ``esp_deep_sleep_start`` function will power down all RTC power doma
 
 Note: on the first revision of the ESP32, RTC fast memory will always be kept enabled in deep sleep, so that the deep sleep stub can run after reset. This can be overriden, if the application doesn't need clean reset behaviour after deep sleep.
 
+If some variables in the program are placed into RTC slow memory (for example, using ``RTC_DATA_ATTR`` attribute), RTC slow memory will be kept powered on by default. This can be overriden using ``esp_deep_sleep_pd_config`` function, if desired.
+
 .. doxygenfunction:: esp_deep_sleep_pd_config
 .. doxygenenum:: esp_deep_sleep_pd_domain_t
 .. doxygenenum:: esp_deep_sleep_pd_option_t