issues with implementing SPI slave on nrf9160DK

using nrf connect sdk 1.4.0 and nrf9160 DK

build: nrf9160dk_nrf9160ns

SES version: V5.10d

Windows 10 Pro 64bit

1. Please note I used https_client project to implement spi slave(but have removed all the https code.. ignore the cert file)

2. Used some details from tickets this and this.. Please trust me when I say i have searched the devzone and documents as much as I could

proj.conf looks like this

# SPI
CONFIG_SPI=y
## for slave only
CONFIG_SPI_SLAVE=y
CONFIG_SPI_3_OP_MODES=3

#commented these out as per some devzone discussions
#CONFIG_SPI_3=y
#CONFIG_SPI_NRFX=y
#CONFIG_SPI_3_NRF_SPIS=y #this gives an error while opening a project if uncommented

CONFIG_RESET_ON_FATAL_ERROR=n

overlay file

&spi3 {
compatible = "nordic,nrf-spis";
status = "okay";
mosi-pin = <10>;
miso-pin = <11>;
sck-pin = <12>;
csn-pin = <13>;
def-char = <0xde>;
};

main.c

/*
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-BSD-5-Clause-Nordic
 */

#include <string.h>
#include <zephyr.h>
#include <stdlib.h>
#include <drivers/spi.h>
#include <nrfx.h>
#include <nrfx_uarte.h>
#include "nrfx_spis.h"

#define PIN_SCK 10
#define PIN_MOSI 11
#define PIN_MISO 12
#define PIN_CSN 13
#define SPIS_NR 3

nrfx_spis_t spis_t = NRFX_SPIS_INSTANCE(SPIS_NR);
nrfx_spis_config_t spis_config_t = NRFX_SPIS_DEFAULT_CONFIG(PIN_SCK,PIN_MOSI,PIN_MISO,PIN_CSN);

uint8_t rx_buffer[2] = {0x0};
uint8_t tx_buffer[2] = {0xa5};

void spis_event_handler_t(nrfx_spis_evt_t const *p_event, void *p_context){
    printk("handler\n");
    int err;
    switch(p_event->evt_type){
        case NRFX_SPIS_XFER_DONE:
                printk("received %x, %x\n",rx_buffer[0], rx_buffer[1]);
            err = nrfx_spis_buffers_set(&spis_t, tx_buffer, sizeof(tx_buffer), rx_buffer, sizeof(rx_buffer));
            if(err != NRFX_SUCCESS){
                printk("Error with setting.\n");
            }
            break;
        case NRFX_SPIS_BUFFERS_SET_DONE:
            printk("buffers set\n");
            break;
        case NRFX_SPIS_EVT_TYPE_MAX:
        
            break;
        default:
            ;
    }
}

static void manual_isr_setup()
{
    //IRQ_DIRECT_CONNECT(SPIM3_SPIS3_TWIM3_TWIS3_UARTE3_IRQn, 0, nrfx_spis_3_irq_handler, 0);
    //irq_enable(SPIM3_SPIS3_TWIM3_TWIS3_UARTE3_IRQn);
    IRQ_DIRECT_CONNECT(UARTE3_SPIM3_SPIS3_TWIM3_TWIS3_IRQn, 0, nrfx_spis_3_irq_handler, 0);
    irq_enable(UARTE3_SPIM3_SPIS3_TWIM3_TWIS3_IRQn);    
}

void init_spis(){
    int err;

    //change mode
    spis_config_t.mode = NRF_SPIS_MODE_3;
    err = nrfx_spis_init(&spis_t,&spis_config_t,spis_event_handler_t,NULL);
    if(err != NRFX_SUCCESS){
        printk("nrfx_spis_init - Error. %x\n",err);
    } else {
        printk("SPIS started.\n");
    }
}


void spi_slave_test(void) {
    int err;
    init_spis();
    manual_isr_setup();

    err = nrfx_spis_buffers_set(&spis_t, tx_buffer, sizeof(tx_buffer), rx_buffer, sizeof(rx_buffer));
    if(err != NRFX_SUCCESS){
        printk("nrfx_spis_buffers_set - Error. %x\n", err);
    }
}


void main(void)
{
	printk("SPIS sample started \n\r");
        spi_slave_test();
        while (1) {
          //printk("alive \n");
          k_sleep(Z_TIMEOUT_TICKS(50000));
        }
}

Notes:

I have closed the solution and opened after changing proj.conf. I am using SPIS3

Issue is that nrfx_spis_init fails with error 0xbad0005.. and the reason for that is this line in nrfx_spi.c fails

    if (p_cb->state != NRFX_DRV_STATE_UNINITIALIZED)

I am just confused to see that p_cb->state is set to NRFX_DRV_STATE for some reason
m_cb[p_instance->drv_inst_idx] has valid data... that array has ONLY ONE element (given only spi3 is available)  and drv_inst_idx=0;

It is clear that I a missing some configuration.. I was told to make some spis related changes using the SES ->project->configure nrf sdk project.. I tried to enable spis2 instance and spis3 driver and that made no difference.. I am sure you have some document in there somewhere in your ocean of documents explaining this but unfortunately I couldn't find any details

3. The SPI master worked without any issue.. Not that it helps but just FYI

4. attached the entire project in zip file