bugfix(flash): improve spi cs timing settings for flash

cs setup time is recomemded to be 1.5T, and cs hold time is recommended to be 2.5T.
(cs_setup = 1, cs_setup_time = 0; cs_hold = 1, cs_hold_time = 1)

components/bootloader_support/include/bootloader_common.h

@@ -141,3 +141,11 @@ esp_err_t bootloader_common_get_partition_description(const esp_partition_pos_t
  * @brief Configure VDDSDIO, call this API to rise VDDSDIO to 1.9V when VDDSDIO regulator is enabled as 1.8V mode.
  */
 void bootloader_common_vddsdio_configure();
+
+/**
+ * @brief Set the flash CS setup and hold time.
+ *
+ * CS setup time is recomemded to be 1.5T, and CS hold time is recommended to be 2.5T.
+ * cs_setup = 1, cs_setup_time = 0; cs_hold = 1, cs_hold_time = 1
+ */
+void bootloader_common_set_flash_cs_timing();

components/bootloader_support/src/bootloader_common.c

@@ -29,6 +29,7 @@
 #include "soc/gpio_periph.h"
 #include "soc/efuse_reg.h"
 #include "soc/rtc.h"
+#include "soc/spi_reg.h"
 #include "esp_image_format.h"
 #include "bootloader_sha.h"
 #include "sys/param.h"
@@ -274,3 +275,13 @@ void bootloader_common_vddsdio_configure()
     }
 #endif // CONFIG_BOOTLOADER_VDDSDIO_BOOST
 }
+
+void bootloader_common_set_flash_cs_timing()
+{
+    SET_PERI_REG_MASK(SPI_USER_REG(0), SPI_CS_HOLD_M | SPI_CS_SETUP_M);
+    SET_PERI_REG_BITS(SPI_CTRL2_REG(0), SPI_HOLD_TIME_V, 1, SPI_HOLD_TIME_S);
+    SET_PERI_REG_BITS(SPI_CTRL2_REG(0), SPI_SETUP_TIME_V, 0, SPI_SETUP_TIME_S);
+    SET_PERI_REG_MASK(SPI_USER_REG(1), SPI_CS_HOLD_M | SPI_CS_SETUP_M);
+    SET_PERI_REG_BITS(SPI_CTRL2_REG(1), SPI_HOLD_TIME_V, 1, SPI_HOLD_TIME_S);
+    SET_PERI_REG_BITS(SPI_CTRL2_REG(1), SPI_SETUP_TIME_V, 0, SPI_SETUP_TIME_S);
+}

components/bootloader_support/src/bootloader_init.c

@@ -393,6 +393,9 @@ static void IRAM_ATTR flash_gpio_configure(const esp_image_header_t* pfhdr)
             #endif
         }
     }
+
+    // improve the flash cs timing.
+    bootloader_common_set_flash_cs_timing();
 }
 
 static void uart_console_configure(void)

components/esp32/cpu_start.c

@@ -72,6 +72,7 @@
 #include "pm_impl.h"
 #include "trax.h"
 #include "esp_ota_ops.h"
+#include "bootloader_common.h"
 
 #define STRINGIFY(s) STRINGIFY2(s)
 #define STRINGIFY2(s) #s
@@ -173,6 +174,8 @@ void IRAM_ATTR call_start_cpu0()
         abort();
 #endif
     }
+# else  // If psram is uninitialized, we need to improve the flash cs timing.
+    bootloader_common_set_flash_cs_timing();
 #endif
 
     ESP_EARLY_LOGI(TAG, "Pro cpu up.");