Send release power-down (0xAB) instruction, to revive flash, that might be in power-down state

src/rp2040/boot_stage2/boot2_at25sf128a.S

@@ -80,6 +80,7 @@
 #define CMD_READ_STATUS2 0x35
 #define CMD_WRITE_STATUS 0x01
 #define CMD_WRITE_STATUS2 0x31
+#define CMD_RELEASE_POWERDOWN 0xAB
 #define SREG_DATA 0x02  // Enable quad-SPI mode
 
 // ----------------------------------------------------------------------------
@@ -147,10 +148,20 @@ program_sregs:
     ldr r1, =(CTRL0_SPI_TXRX)
     str r1, [r3, #SSI_CTRLR0_OFFSET]
 
-     // Enable SSI and select slave 0
+    // Enable SSI and select slave 0
     movs r1, #1
     str r1, [r3, #SSI_SSIENR_OFFSET]
 
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Send release power-down command, discard RX
+    movs r1, #CMD_RELEASE_POWERDOWN
+    str r1, [r3, #SSI_DR0_OFFSET]
+
+    // Poll for completion and discard RX
+    bl wait_ssi_ready
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+#endif
+
     // Check whether SR needs updating
     movs r0, #CMD_READ_STATUS2
     bl read_flash_sreg

src/rp2040/boot_stage2/boot2_generic_03h.S

@@ -36,6 +36,7 @@ pico_default_asm_setup
 #endif
 
 #define CMD_READ 0x03
+#define CMD_RELEASE_POWERDOWN 0xAB
 
 // Value is number of address bits divided by 4
 #define ADDR_L 6
@@ -92,13 +93,28 @@ regular_func _stage2_boot
     movs r1, #1
     str r1, [r3, #SSI_SSIENR_OFFSET]
 
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Send release power-down command, discard RX
+    movs r1, #CMD_RELEASE_POWERDOWN
+    str r1, [r3, #SSI_DR0_OFFSET]
+
+    // Poll for completion and discard RX
+    bl wait_ssi_ready
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+#endif
+
 // We are now in XIP mode. Any bus accesses to the XIP address window will be
 // translated by the SSI into 03h read commands to the external flash (if cache is missed),
 // and the data will be returned to the bus.
 
 // Pull in standard exit routine
 #include "boot2_helpers/exit_from_boot2.S"
 
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+// Common functions
+#include "boot2_helpers/wait_ssi_ready.S"
+#endif
+
 .global literals
 literals:
 .ltorg

src/rp2040/boot_stage2/boot2_is25lp080.S

@@ -74,6 +74,7 @@
 #define CMD_WRITE_ENABLE 0x06
 #define CMD_READ_STATUS 0x05
 #define CMD_WRITE_STATUS 0x01
+#define CMD_RELEASE_POWERDOWN 0xAB
 #define SREG_DATA 0x40  // Enable quad-SPI mode
 
 // ----------------------------------------------------------------------------
@@ -114,10 +115,20 @@ program_sregs:
     ldr r1, =(CTRL0_SPI_TXRX)
     str r1, [r3, #SSI_CTRLR0_OFFSET]
 
-     // Enable SSI and select slave 0
+    // Enable SSI and select slave 0
     movs r1, #1
     str r1, [r3, #SSI_SSIENR_OFFSET]
 
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Send release power-down command, discard RX
+    movs r1, #CMD_RELEASE_POWERDOWN
+    str r1, [r3, #SSI_DR0_OFFSET]
+
+    // Poll for completion and discard RX
+    bl wait_ssi_ready
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+#endif
+
     // Check whether SR needs updating
     ldr r0, =CMD_READ_STATUS
     bl read_flash_sreg

src/rp2040/boot_stage2/boot2_w25q080.S

@@ -80,6 +80,7 @@
 #define CMD_READ_STATUS 0x05
 #define CMD_READ_STATUS2 0x35
 #define CMD_WRITE_STATUS 0x01
+#define CMD_RELEASE_POWERDOWN 0xAB
 #define SREG_DATA 0x02  // Enable quad-SPI mode
 
 // ----------------------------------------------------------------------------
@@ -147,10 +148,20 @@ program_sregs:
     ldr r1, =(CTRL0_SPI_TXRX)
     str r1, [r3, #SSI_CTRLR0_OFFSET]
 
-     // Enable SSI and select slave 0
+    // Enable SSI and select slave 0
     movs r1, #1
     str r1, [r3, #SSI_SSIENR_OFFSET]
 
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Send release power-down command, discard RX
+    movs r1, #CMD_RELEASE_POWERDOWN
+    str r1, [r3, #SSI_DR0_OFFSET]
+
+    // Poll for completion and discard RX
+    bl wait_ssi_ready
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+#endif
+
     // Check whether SR needs updating
     movs r0, #CMD_READ_STATUS2
     bl read_flash_sreg

src/rp2040/boot_stage2/include/boot_stage2/config.h

@@ -11,6 +11,11 @@
 
 #include "pico.h"
 
+// PICO_CONFIG: PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN, Release the flash device from power-down state during boot stage 2, type=bool, default=0, group=boot_stage2
+#ifndef PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+#define PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN 0
+#endif
+
 // PICO_CONFIG: PICO_BUILD_BOOT_STAGE2_NAME, Name of the boot stage 2 if selected in the build system, group=boot_stage2
 #ifdef PICO_BUILD_BOOT_STAGE2_NAME
     #define _BOOT_STAGE2_SELECTED

src/rp2350/boot_stage2/boot2_generic_03h.S

@@ -47,6 +47,7 @@
 #endif
 
 #define CMD_READ 0x03
+#define CMD_RELEASE_POWERDOWN 0xAB
 
 // ----------------------------------------------------------------------------
 // Register initialisation values -- same in Arm/RISC-V code.
@@ -60,6 +61,15 @@
 // CLKDIV and RXDELAY, and no constraints on CS max assertion, CS min
 // deassertion, or page boundary burst breaks.
 
+// Need to use direct serial mode to send SR commands. Choose a
+// conservative direct-mode divisor (5 MHz at 150 MHz clk_sys)
+// since the XIP-mode divisor may be unsafe without an RX delay.
+#define INIT_DIRECT_CSR (\
+    30 << QMI_DIRECT_CSR_CLKDIV_LSB | \
+    QMI_DIRECT_CSR_EN_BITS | \
+    QMI_DIRECT_CSR_AUTO_CS0N_BITS | \
+0)
+
 #define INIT_M0_TIMING (\
     1                      << QMI_M0_TIMING_COOLDOWN_LSB |\
     PICO_FLASH_SPI_RXDELAY << QMI_M0_TIMING_RXDELAY_LSB |\
@@ -100,6 +110,27 @@ regular_func _stage2_boot
     sw a0, QMI_M0_RCMD_OFFSET(a3)
     li a0, INIT_M0_RFMT
     sw a0, QMI_M0_RFMT_OFFSET(a3)
+
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Need to use direct serial mode to send commands.
+    li a1, INIT_DIRECT_CSR
+    sw a1, QMI_DIRECT_CSR_OFFSET(a3)
+    // Wait for cooldown on last XIP transfer to expire, by polling BUSY
+1:
+    lw a1, QMI_DIRECT_CSR_OFFSET(a3)
+    andi a1, a1, QMI_DIRECT_CSR_BUSY_BITS
+    bnez a1, 1b
+
+    // Send release power-down command, discard RX
+    li a0, CMD_RELEASE_POWERDOWN
+    sw a0, QMI_DIRECT_TX_OFFSET(a3)
+    jal wait_qmi_ready
+    lw a0, QMI_DIRECT_RX_OFFSET(a3)
+
+    // Disable direct mode
+    andi a1, a1, ~QMI_DIRECT_CSR_EN_BITS
+    sw a1, QMI_DIRECT_CSR_OFFSET(a3)
+#endif
 #else
     push {lr}
     ldr r3, =XIP_QMI_BASE
@@ -109,11 +140,37 @@ regular_func _stage2_boot
     str r0, [r3, #QMI_M0_RCMD_OFFSET]
     ldr r0, =INIT_M0_RFMT
     str r0, [r3, #QMI_M0_RFMT_OFFSET]
+
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Need to use direct serial mode to send commands.
+    ldr r1, =INIT_DIRECT_CSR
+    str r1, [r3, #QMI_DIRECT_CSR_OFFSET]
+    // Wait for cooldown on last XIP transfer to expire, by polling BUSY
+1:
+    ldr r0, [r3, #QMI_DIRECT_CSR_OFFSET]
+    tst r0, #QMI_DIRECT_CSR_BUSY_BITS
+    bne 1b
+
+    // Send release power-down command, discard RX
+    movs r0, #CMD_RELEASE_POWERDOWN
+    str r0, [r3, #QMI_DIRECT_TX_OFFSET]
+    bl wait_qmi_ready
+    ldr r0, [r3, #QMI_DIRECT_RX_OFFSET]
+
+    // Disable direct mode
+    bics r1, #QMI_DIRECT_CSR_EN_BITS
+    str r1, [r3, #QMI_DIRECT_CSR_OFFSET]
+#endif
 #endif
 
 // Pull in standard exit routine
 #include "boot2_helpers/exit_from_boot2.S"
 
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+// Common functions
+#include "boot2_helpers/wait_qmi_ready.S"
+#endif
+
 #ifndef __riscv
 .global literals
 literals:

src/rp2350/boot_stage2/boot2_w25q080.S

@@ -85,6 +85,7 @@
 #define CMD_READ_STATUS 0x05
 #define CMD_READ_STATUS2 0x35
 #define CMD_WRITE_STATUS 0x01
+#define CMD_RELEASE_POWERDOWN 0xAB
 #define SREG_DATA 0x02  // Enable quad-SPI mode
 
 // ----------------------------------------------------------------------------
@@ -176,6 +177,14 @@ program_sregs:
     lw a1, QMI_DIRECT_CSR_OFFSET(a3)
     andi a1, a1, QMI_DIRECT_CSR_BUSY_BITS
     bnez a1, 1b
+
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Send release power-down command, discard RX
+    li a0, CMD_RELEASE_POWERDOWN
+    sw a0, QMI_DIRECT_TX_OFFSET(a3)
+    jal wait_qmi_ready
+    lw a0, QMI_DIRECT_RX_OFFSET(a3)
+#endif
 
     // Check whether SR needs updating
     li a0, CMD_READ_STATUS2
@@ -268,6 +277,14 @@ program_sregs:
     ldr r0, [r3, #QMI_DIRECT_CSR_OFFSET]
     tst r0, #QMI_DIRECT_CSR_BUSY_BITS
     bne 1b
+
+#if PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+    // Send release power-down command, discard RX
+    movs r0, #CMD_RELEASE_POWERDOWN
+    str r0, [r3, #QMI_DIRECT_TX_OFFSET]
+    bl wait_qmi_ready
+    ldr r0, [r3, #QMI_DIRECT_RX_OFFSET]
+#endif
 
     // Check whether SR needs updating
     movs r0, #CMD_READ_STATUS2

src/rp2350/boot_stage2/include/boot_stage2/config.h

@@ -11,6 +11,11 @@
 
 #include "pico/config.h"
 
+// PICO_CONFIG: PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN, Release the flash device from power-down state during boot stage 2, type=bool, default=0, group=boot_stage2
+#ifndef PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN
+#define PICO_BOOT_STAGE2_FLASH_RELEASE_POWERDOWN 0
+#endif
+
 // PICO_CONFIG: PICO_BUILD_BOOT_STAGE2_NAME, Name of the boot stage 2 if selected in the build system, group=boot_stage2
 #ifdef PICO_BUILD_BOOT_STAGE2_NAME
     #define _BOOT_STAGE2_SELECTED