PicoPlusPsram.cpp

#include "pico/stdlib.h"
#include "boards/pimoroni_pico_plus2_rp2350.h"
#include "hardware/structs/ioqspi.h"
#include "hardware/structs/qmi.h"
#include "hardware/structs/xip_ctrl.h"
#include "hardware/clocks.h"
#include "hardware/sync.h"

#include "PicoPlusPsram.h"

#define PSRAM_LOCATION _u(0x11000000)

// Private constructor
PicoPlusPsram::PicoPlusPsram(void)
{
  // initialise psram
  m_uMemorySize = Init(PIMORONI_PICO_PLUS2_PSRAM_CS_PIN);

  if(m_uMemorySize)
  {
    static lwmem_region_t regions[] = 
    {
        {(void *)PSRAM_LOCATION, m_uMemorySize}, 
        {nullptr, 0}
    };

    lwmem_assignmem(regions);
  }
}


size_t __no_inline_not_in_flash_func(PicoPlusPsram::Detect)(void) 
{
    int psram_size = 0;

    uint32_t intr_stash = save_and_disable_interrupts();

    // Try and read the PSRAM ID via direct_csr.
    qmi_hw->direct_csr = 30 << QMI_DIRECT_CSR_CLKDIV_LSB | QMI_DIRECT_CSR_EN_BITS;

    // Need to poll for the cooldown on the last XIP transfer to expire
    // (via direct-mode BUSY flag) before it is safe to perform the first
    // direct-mode operation
    while ((qmi_hw->direct_csr & QMI_DIRECT_CSR_BUSY_BITS) != 0) {
    }

    // Exit out of QMI in case we've inited already
    qmi_hw->direct_csr |= QMI_DIRECT_CSR_ASSERT_CS1N_BITS;

    // Transmit as quad.
    qmi_hw->direct_tx = QMI_DIRECT_TX_OE_BITS | QMI_DIRECT_TX_IWIDTH_VALUE_Q << QMI_DIRECT_TX_IWIDTH_LSB | 0xf5;

    while ((qmi_hw->direct_csr & QMI_DIRECT_CSR_BUSY_BITS) != 0) {
    }

    (void)qmi_hw->direct_rx;

    qmi_hw->direct_csr &= ~(QMI_DIRECT_CSR_ASSERT_CS1N_BITS);

    // Read the id
    qmi_hw->direct_csr |= QMI_DIRECT_CSR_ASSERT_CS1N_BITS;
    uint8_t kgd = 0;
    uint8_t eid = 0;

    for (size_t i = 0; i < 7; i++)
    {
        if (i == 0) {
            qmi_hw->direct_tx = 0x9f;
        } else {
            qmi_hw->direct_tx = 0xff;
        }

        while ((qmi_hw->direct_csr & QMI_DIRECT_CSR_TXEMPTY_BITS) == 0) {
        }

        while ((qmi_hw->direct_csr & QMI_DIRECT_CSR_BUSY_BITS) != 0) {
        }

        if (i == 5) {
            kgd = qmi_hw->direct_rx;
        } else if (i == 6) {
            eid = qmi_hw->direct_rx;
        } else {
            (void)qmi_hw->direct_rx;
        }
    }

    // Disable direct csr.
    qmi_hw->direct_csr &= ~(QMI_DIRECT_CSR_ASSERT_CS1N_BITS | QMI_DIRECT_CSR_EN_BITS);

    if (kgd == 0x5D) {
        psram_size = 1024 * 1024; // 1 MiB
        uint8_t size_id = eid >> 5;
        if (eid == 0x26 || size_id == 2) {
            psram_size *= 8; // 8 MiB
        } else if (size_id == 0) {
            psram_size *= 2; // 2 MiB
        } else if (size_id == 1) {
            psram_size *= 4; // 4 MiB
        }
    }

    restore_interrupts(intr_stash);
    return psram_size;
}

size_t __no_inline_not_in_flash_func(PicoPlusPsram::Init)(uint cs_pin) 
{
    gpio_set_function(cs_pin, GPIO_FUNC_XIP_CS1);

    size_t psram_size = Detect();

    if (!psram_size) {
        return 0;
    }

    // Enable direct mode, PSRAM CS, clkdiv of 10.
    qmi_hw->direct_csr = 10 << QMI_DIRECT_CSR_CLKDIV_LSB | \
        QMI_DIRECT_CSR_EN_BITS | \
        QMI_DIRECT_CSR_AUTO_CS1N_BITS;
    while (qmi_hw->direct_csr & QMI_DIRECT_CSR_BUSY_BITS) {
        ;
    }

    // Enable QPI mode on the PSRAM
    const uint CMD_QPI_EN = 0x35;
    qmi_hw->direct_tx = QMI_DIRECT_TX_NOPUSH_BITS | CMD_QPI_EN;

    while (qmi_hw->direct_csr & QMI_DIRECT_CSR_BUSY_BITS) {
        ;
    }

    // Set PSRAM timing for APS6404
    //
    // Using an rxdelay equal to the divisor isn't enough when running the APS6404 close to 133MHz.
    // So: don't allow running at divisor 1 above 100MHz (because delay of 2 would be too late),
    // and add an extra 1 to the rxdelay if the divided clock is > 100MHz (i.e. sys clock > 200MHz).
    const int max_psram_freq = 133000000;
    const int clock_hz = clock_get_hz(clk_sys);
    int divisor = (clock_hz + max_psram_freq - 1) / max_psram_freq;
    if (divisor == 1 && clock_hz > 100000000) {
        divisor = 2;
    }
    int rxdelay = divisor;
    if (clock_hz / divisor > 100000000) {
        rxdelay += 1;
    }

    // - Max select must be <= 8us.  The value is given in multiples of 64 system clocks.
    // - Min deselect must be >= 18ns.  The value is given in system clock cycles - ceil(divisor / 2).
    const int clock_period_fs = 1000000000000000ll / clock_hz;
    const int max_select = (125 * 1000000) / clock_period_fs;  // 125 = 8000ns / 64
    const int min_deselect = (18 * 1000000 + (clock_period_fs - 1)) / clock_period_fs - (divisor + 1) / 2;

    qmi_hw->m[1].timing = 1 << QMI_M1_TIMING_COOLDOWN_LSB |
        QMI_M1_TIMING_PAGEBREAK_VALUE_1024 << QMI_M1_TIMING_PAGEBREAK_LSB |
        max_select << QMI_M1_TIMING_MAX_SELECT_LSB |
        min_deselect << QMI_M1_TIMING_MIN_DESELECT_LSB |
        rxdelay << QMI_M1_TIMING_RXDELAY_LSB |
        divisor << QMI_M1_TIMING_CLKDIV_LSB;

    // Set PSRAM commands and formats
    qmi_hw->m[1].rfmt =
        QMI_M0_RFMT_PREFIX_WIDTH_VALUE_Q << QMI_M0_RFMT_PREFIX_WIDTH_LSB | \
            QMI_M0_RFMT_ADDR_WIDTH_VALUE_Q << QMI_M0_RFMT_ADDR_WIDTH_LSB | \
            QMI_M0_RFMT_SUFFIX_WIDTH_VALUE_Q << QMI_M0_RFMT_SUFFIX_WIDTH_LSB | \
            QMI_M0_RFMT_DUMMY_WIDTH_VALUE_Q << QMI_M0_RFMT_DUMMY_WIDTH_LSB | \
            QMI_M0_RFMT_DATA_WIDTH_VALUE_Q << QMI_M0_RFMT_DATA_WIDTH_LSB | \
            QMI_M0_RFMT_PREFIX_LEN_VALUE_8 << QMI_M0_RFMT_PREFIX_LEN_LSB | \
            6 << QMI_M0_RFMT_DUMMY_LEN_LSB;

    qmi_hw->m[1].rcmd = 0xEB;

    qmi_hw->m[1].wfmt =
        QMI_M0_WFMT_PREFIX_WIDTH_VALUE_Q << QMI_M0_WFMT_PREFIX_WIDTH_LSB | \
            QMI_M0_WFMT_ADDR_WIDTH_VALUE_Q << QMI_M0_WFMT_ADDR_WIDTH_LSB | \
            QMI_M0_WFMT_SUFFIX_WIDTH_VALUE_Q << QMI_M0_WFMT_SUFFIX_WIDTH_LSB | \
            QMI_M0_WFMT_DUMMY_WIDTH_VALUE_Q << QMI_M0_WFMT_DUMMY_WIDTH_LSB | \
            QMI_M0_WFMT_DATA_WIDTH_VALUE_Q << QMI_M0_WFMT_DATA_WIDTH_LSB | \
            QMI_M0_WFMT_PREFIX_LEN_VALUE_8 << QMI_M0_WFMT_PREFIX_LEN_LSB;

    qmi_hw->m[1].wcmd = 0x38;

    // Disable direct mode
    qmi_hw->direct_csr = 0;

    // Enable writes to PSRAM
    hw_set_bits(&xip_ctrl_hw->ctrl, XIP_CTRL_WRITABLE_M1_BITS);

    return psram_size;
}