QSPIF: Add back enable_fast_mode

This function writes a "config" register to ensure that the flash part
is in high performance mode, not low-power mode. This is required at
by at least MX25R6435F in order to operate at frequencies > 33MHz
(for reference, DISCO_L475VG_IOT01A runs the QSPI interface at 80 MHz).
The config register that this writes does not appear to be covered by
the SFDP spec (JESD216D.01) so this remains the status quo of
unconditional execution, as has been done on master since #8352.

Author: Kyle Kearney

components/storage/blockdevice/COMPONENT_QSPIF/QSPIFBlockDevice.cpp

@@ -716,6 +716,7 @@ int QSPIFBlockDevice::_sfdp_parse_basic_param_table(uint32_t basic_table_addr, s
     // Detect and Set fastest Bus mode (default 1-1-1)
     _sfdp_detect_best_bus_read_mode(param_table, basic_table_size, shouldSetQuadEnable, is_qpi_mode);
     if (true == shouldSetQuadEnable) {
+        _enable_fast_mode();
         // Set Quad Enable and QPI Bus modes if Supported
         tr_debug("Init - Setting Quad Enable");
         if (0 != _sfdp_set_quad_enabled(param_table)) {
@@ -1279,6 +1280,73 @@ int QSPIFBlockDevice::_set_write_enable()
     return status;
 }
 
+int QSPIFBlockDevice::_enable_fast_mode()
+{
+    const int NUM_REGISTERS = QSPI_STATUS_REGISTER_COUNT + 1; // Status registers + one config register
+    char status_reg[NUM_REGISTERS] = {0};
+    unsigned int read_conf_register_inst = 0x15;
+    char status_reg_qer_setup[NUM_REGISTERS] = {0};
+
+    status_reg_qer_setup[2] = 0x2; // Bit 1 of config Reg 2
+
+    // Configure  BUS Mode to 1_1_1 for all commands other than Read
+    if (QSPI_STATUS_OK != _qspi.configure_format(QSPI_CFG_BUS_SINGLE, QSPI_CFG_BUS_SINGLE, QSPI_CFG_ADDR_SIZE_24, QSPI_CFG_BUS_SINGLE,
+                                                 0, QSPI_CFG_BUS_SINGLE, 0)) {
+        tr_error("_qspi_configure_format failed");
+        return -1;
+
+    }
+
+    // Read Status Register
+    if (QSPI_STATUS_OK == _qspi_send_general_command(read_conf_register_inst, QSPI_NO_ADDRESS_COMMAND, NULL, 0,
+                                                     &status_reg[1],
+                                                     NUM_REGISTERS - 1)) {  // store received values in status_value
+        tr_debug("Reading Config Register Success: value = 0x%x", (int)status_reg[2]);
+    } else {
+        tr_error("Reading Config Register failed");
+        return -1;
+    }
+
+    // Set Bits for Quad Enable
+    for (int i = 0; i < NUM_REGISTERS; i++) {
+        status_reg[i] |= status_reg_qer_setup[i];
+    }
+
+    // Write new Status Register Setup
+    if (_set_write_enable() != 0) {
+        tr_error("Write Enabe failed");
+        return -1;
+    }
+
+    if (QSPI_STATUS_OK == _qspi_send_general_command(QSPIF_INST_WSR1, QSPI_NO_ADDRESS_COMMAND, status_reg,
+                                                     NUM_REGISTERS, NULL,
+                                                     0)) {   // Write Fast mode bit to status_register
+        tr_debug("fast mode enable - Writing Config Register Success: value = 0x%x",
+                 (int)status_reg[2]);
+    } else {
+        tr_error("fast mode enable - Writing Config Register failed");
+        return -1;
+    }
+
+    if (false == _is_mem_ready()) {
+        tr_error("Device not ready after write, failed");
+        return -1;
+    }
+
+    // For Debug
+    memset(status_reg, 0, NUM_REGISTERS);
+    if (QSPI_STATUS_OK == _qspi_send_general_command(read_conf_register_inst, QSPI_NO_ADDRESS_COMMAND, NULL, 0,
+                                                     &status_reg[1],
+                                                     NUM_REGISTERS - 1)) {  // store received values in status_value
+        tr_debug("Verifying Config Register Success: value = 0x%x", (int)status_reg[2]);
+    } else {
+        tr_error("Verifying Config Register failed");
+        return -1;
+    }
+
+    return 0;
+}
+
 bool QSPIFBlockDevice::_is_mem_ready()
 {
     // Check Status Register Busy Bit to Verify the Device isn't Busy

components/storage/blockdevice/COMPONENT_QSPIF/QSPIFBlockDevice.h

@@ -275,6 +275,9 @@ class QSPIFBlockDevice : public mbed::BlockDevice {
     // Wait on status register until write not-in-progress
     bool _is_mem_ready();
 
+    // Enable Fast Mode - for flash chips with low power default
+    int _enable_fast_mode();
+
     /****************************************/
     /* SFDP Detection and Parsing Functions */
     /****************************************/