blob: fda0f992f850401974caa145a47d8296e9e51e81 [file] [log] [blame]
// ----------------------------------------------------------------------------
// Copyright (c) 2019-2021 Raspberry Pi (Trading) Ltd.
// SPDX-License-Identifier: BSD-3-Clause
//
// Device: ISSI IS25LP080D
// Based on W25Q080 code: main difference is the QE bit being in
// SR1 instead of SR2.
//
// Description: Configures IS25LP080D to run in Quad I/O continuous read XIP mode
//
// Details: * Check status register to determine if QSPI mode is enabled,
// and perform an SR programming cycle if necessary.
// * Use SSI to perform a dummy 0xEB read command, with the mode
// continuation bits set, so that the flash will not require
// 0xEB instruction prefix on subsequent reads.
// * Configure SSI to write address, mode bits, but no instruction.
// SSI + flash are now jointly in a state where continuous reads
// can take place.
// * Set VTOR = 0x10000100 (user vector table immediately after
// this boot2 image).
// * Read stack pointer (MSP) and reset vector from the flash
// vector table; set SP and jump, as though the processor had
// booted directly from flash.
//
// Building: * This code must be linked to run at 0x20027f00
// * The code will be padded to a size of 256 bytes, including a
// 4-byte checksum. Therefore code size cannot exceed 252 bytes.
// ----------------------------------------------------------------------------
#include "pico/asm_helper.S"
#include "hardware/regs/addressmap.h"
#include "hardware/regs/ssi.h"
// ----------------------------------------------------------------------------
// Config section
// ----------------------------------------------------------------------------
// It should be possible to support most flash devices by modifying this section
// The serial flash interface will run at clk_sys/PICO_FLASH_SPI_CLKDIV.
// This must be a positive, even integer.
// The bootrom is very conservative with SPI frequency, but here we should be
// as aggressive as possible.
#ifndef PICO_FLASH_SPI_CLKDIV
#define PICO_FLASH_SPI_CLKDIV 4
#endif
// Define interface width: single/dual/quad IO
#define FRAME_FORMAT SSI_CTRLR0_SPI_FRF_VALUE_QUAD
// For W25Q080 this is the "Read data fast quad IO" instruction:
#define CMD_READ 0xeb
// "Mode bits" are 8 special bits sent immediately after
// the address bits in a "Read Data Fast Quad I/O" command sequence.
// On W25Q080, the four LSBs are don't care, and if MSBs == 0xa, the
// next read does not require the 0xeb instruction prefix.
#define MODE_CONTINUOUS_READ 0xa0
// The number of address + mode bits, divided by 4 (always 4, not function of
// interface width).
#define ADDR_L 8
// How many clocks of Hi-Z following the mode bits. For W25Q080, 4 dummy cycles
// are required.
#define WAIT_CYCLES 4
// If defined, we will read status reg, compare to SREG_DATA, and overwrite
// with our value if the SR doesn't match.
// This isn't great because it will remove block protections.
// A better solution is to use a volatile SR write if your device supports it.
#define PROGRAM_STATUS_REG
#define CMD_WRITE_ENABLE 0x06
#define CMD_READ_STATUS 0x05
#define CMD_WRITE_STATUS 0x01
#define SREG_DATA 0x40 // Enable quad-SPI mode
// ----------------------------------------------------------------------------
// Start of 2nd Stage Boot Code
// ----------------------------------------------------------------------------
pico_default_asm_setup
.section .text
// lr will be zero on entry if entered from the bootrom, and the boot_stage2 is expected
// to continue into the binary via the vector table at 0x10000100.
//
// lr will be non-zero on entry if this code has been copied into RAM by user code and called
// from there, and the boot_stage2 should just return normally.
//
// r3 holds SSI base, r0...2 used as temporaries. Other GPRs not used.
regular_func _stage2_boot
push {lr}
ldr r3, =XIP_SSI_BASE // Use as base address where possible
// Disable SSI to allow further config
movs r1, #0
str r1, [r3, #SSI_SSIENR_OFFSET]
// Set baud rate
movs r1, #PICO_FLASH_SPI_CLKDIV
str r1, [r3, #SSI_BAUDR_OFFSET]
// On QSPI parts we usually need a 01h SR-write command to enable QSPI mode
// (i.e. turn WPn and HOLDn into IO2/IO3)
#ifdef PROGRAM_STATUS_REG
program_sregs:
#define CTRL0_SPI_TXRX \
(7 << SSI_CTRLR0_DFS_32_LSB) | /* 8 bits per data frame */ \
(SSI_CTRLR0_TMOD_VALUE_TX_AND_RX << SSI_CTRLR0_TMOD_LSB)
ldr r1, =(CTRL0_SPI_TXRX)
str r1, [r3, #SSI_CTRLR0_OFFSET]
// Enable SSI and select slave 0
movs r1, #1
str r1, [r3, #SSI_SSIENR_OFFSET]
// Check whether SR needs updating
ldr r0, =CMD_READ_STATUS
bl read_flash_sreg
ldr r2, =SREG_DATA
cmp r0, r2
beq skip_sreg_programming
// Send write enable command
movs r1, #CMD_WRITE_ENABLE
str r1, [r3, #SSI_DR0_OFFSET]
// Poll for completion and discard RX
bl wait_ssi_ready
ldr r1, [r3, #SSI_DR0_OFFSET]
// Send status write command followed by data bytes
movs r1, #CMD_WRITE_STATUS
str r1, [r3, #SSI_DR0_OFFSET]
movs r0, #0
str r2, [r3, #SSI_DR0_OFFSET]
bl wait_ssi_ready
ldr r1, [r3, #SSI_DR0_OFFSET]
ldr r1, [r3, #SSI_DR0_OFFSET]
// Poll status register for write completion
1:
ldr r0, =CMD_READ_STATUS
bl read_flash_sreg
movs r1, #1
tst r0, r1
bne 1b
skip_sreg_programming:
// Send a 0xA3 high-performance-mode instruction
// ldr r1, =0xa3
// str r1, [r3, #SSI_DR0_OFFSET]
// bl wait_ssi_ready
// Disable SSI again so that it can be reconfigured
movs r1, #0
str r1, [r3, #SSI_SSIENR_OFFSET]
#endif
// First we need to send the initial command to get us in to Fast Read Quad I/O
// mode. As this transaction requires a command, we can't send it in XIP mode.
// To enter Continuous Read mode as well we need to append 4'b0010 to the address
// bits and then add a further 4 don't care bits. We will construct this by
// specifying a 28-bit address, with the least significant bits being 4'b0010.
// This is just a dummy transaction so we'll perform a read from address zero
// and then discard what comes back. All we really care about is that at the
// end of the transaction, the flash device is in Continuous Read mode
// and from then on will only expect to receive addresses.
dummy_read:
#define CTRLR0_ENTER_XIP \
(FRAME_FORMAT /* Quad I/O mode */ \
<< SSI_CTRLR0_SPI_FRF_LSB) | \
(31 << SSI_CTRLR0_DFS_32_LSB) | /* 32 data bits */ \
(SSI_CTRLR0_TMOD_VALUE_EEPROM_READ /* Send INST/ADDR, Receive Data */ \
<< SSI_CTRLR0_TMOD_LSB)
ldr r1, =(CTRLR0_ENTER_XIP)
str r1, [r3, #SSI_CTRLR0_OFFSET]
movs r1, #0x0 // NDF=0 (single 32b read)
str r1, [r3, #SSI_CTRLR1_OFFSET]
#define SPI_CTRLR0_ENTER_XIP \
(ADDR_L << SSI_SPI_CTRLR0_ADDR_L_LSB) | /* Address + mode bits */ \
(WAIT_CYCLES << SSI_SPI_CTRLR0_WAIT_CYCLES_LSB) | /* Hi-Z dummy clocks following address + mode */ \
(SSI_SPI_CTRLR0_INST_L_VALUE_8B \
<< SSI_SPI_CTRLR0_INST_L_LSB) | /* 8-bit instruction */ \
(SSI_SPI_CTRLR0_TRANS_TYPE_VALUE_1C2A /* Send Command in serial mode then address in Quad I/O mode */ \
<< SSI_SPI_CTRLR0_TRANS_TYPE_LSB)
ldr r1, =(SPI_CTRLR0_ENTER_XIP)
ldr r0, =(XIP_SSI_BASE + SSI_SPI_CTRLR0_OFFSET) // SPI_CTRL0 Register
str r1, [r0]
movs r1, #1 // Re-enable SSI
str r1, [r3, #SSI_SSIENR_OFFSET]
movs r1, #CMD_READ
str r1, [r3, #SSI_DR0_OFFSET] // Push SPI command into TX FIFO
movs r1, #MODE_CONTINUOUS_READ // 32-bit: 24 address bits (we don't care, so 0) and M[7:4]=1010
str r1, [r3, #SSI_DR0_OFFSET] // Push Address into TX FIFO - this will trigger the transaction
// Poll for completion
bl wait_ssi_ready
// At this point CN# will be deasserted and the SPI clock will not be running.
// The Winbond WX25X10CL device will be in continuous read, dual I/O mode and
// only expecting address bits after the next CN# assertion. So long as we
// send 4'b0010 (and 4 more dummy HiZ bits) after every subsequent 24b address
// then the Winbond device will remain in continuous read mode. This is the
// ideal mode for Execute-In-Place.
// (If we want to exit continuous read mode then we will need to switch back
// to APM mode and generate a 28-bit address phase with the extra nibble set
// to 4'b0000).
movs r1, #0
str r1, [r3, #SSI_SSIENR_OFFSET] // Disable SSI (and clear FIFO) to allow further config
// Note that the INST_L field is used to select what XIP data gets pushed into
// the TX FIFO:
// INST_L_0_BITS {ADDR[23:0],XIP_CMD[7:0]} Load "mode bits" into XIP_CMD
// Anything else {XIP_CMD[7:0],ADDR[23:0]} Load SPI command into XIP_CMD
configure_ssi:
#define SPI_CTRLR0_XIP \
(MODE_CONTINUOUS_READ /* Mode bits to keep flash in continuous read mode */ \
<< SSI_SPI_CTRLR0_XIP_CMD_LSB) | \
(ADDR_L << SSI_SPI_CTRLR0_ADDR_L_LSB) | /* Total number of address + mode bits */ \
(WAIT_CYCLES << SSI_SPI_CTRLR0_WAIT_CYCLES_LSB) | /* Hi-Z dummy clocks following address + mode */ \
(SSI_SPI_CTRLR0_INST_L_VALUE_NONE /* Do not send a command, instead send XIP_CMD as mode bits after address */ \
<< SSI_SPI_CTRLR0_INST_L_LSB) | \
(SSI_SPI_CTRLR0_TRANS_TYPE_VALUE_2C2A /* Send Address in Quad I/O mode (and Command but that is zero bits long) */ \
<< SSI_SPI_CTRLR0_TRANS_TYPE_LSB)
ldr r1, =(SPI_CTRLR0_XIP)
ldr r0, =(XIP_SSI_BASE + SSI_SPI_CTRLR0_OFFSET)
str r1, [r0]
movs r1, #1
str r1, [r3, #SSI_SSIENR_OFFSET] // Re-enable SSI
// We are now in XIP mode, with all transactions using Dual I/O and only
// needing to send 24-bit addresses (plus mode bits) for each read transaction.
// Pull in standard exit routine
#include "boot2_helpers/exit_from_boot2.S"
// Common functions
#include "boot2_helpers/wait_ssi_ready.S"
#ifdef PROGRAM_STATUS_REG
#include "boot2_helpers/read_flash_sreg.S"
#endif
.global literals
literals:
.ltorg
.end