STM32L4P5G-DK OSPI speed gets too slow at ClockPrescaler = 0;

[JKim.2]

Hello,

I set 120MHz to OCTOSPI for Octo-SPI PSRAM. With the ClockPrescaler 0x02, the PSRAM test takes several seconds. However, with the ClockPrescaler 0x00, it takes over 3 minutes. Does it mean any problem on the clock configuration of STM32CubeIDE? The .ioc file is attached.

Thanks.

uint8_t BSP_PSRAM_Init(void)
{
OSPIM_CfgTypeDef OSPIM_Cfg_Struct;
OSPI_RegularCmdTypeDef sCommand = {0};
uint8_t reg[2];

if (bsp_psram_initialized == 0)
{

PSRAM_MspInit();

OSPIM_Cfg_Struct.ClkPort = 1;
OSPIM_Cfg_Struct.DQSPort = 1;
OSPIM_Cfg_Struct.IOHighPort = HAL_OSPIM_IOPORT_1_HIGH;
OSPIM_Cfg_Struct.IOLowPort = HAL_OSPIM_IOPORT_1_LOW;
OSPIM_Cfg_Struct.NCSPort = 1;

OSPIM_Cfg_Struct.Req2AckTime = 1;

OSPIPSRAMHandle.Instance = OCTOSPI1;
HAL_OSPI_DeInit(&OSPIPSRAMHandle);

OSPIPSRAMHandle.Init.FifoThreshold = 2;
OSPIPSRAMHandle.Init.DualQuad = HAL_OSPI_DUALQUAD_DISABLE;
OSPIPSRAMHandle.Init.MemoryType = HAL_OSPI_MEMTYPE_APMEMORY;
OSPIPSRAMHandle.Init.DeviceSize = 23; /* 64 MBits */
OSPIPSRAMHandle.Init.ChipSelectHighTime = 1;
OSPIPSRAMHandle.Init.FreeRunningClock = HAL_OSPI_FREERUNCLK_DISABLE;
OSPIPSRAMHandle.Init.ClockMode = HAL_OSPI_CLOCK_MODE_0;
OSPIPSRAMHandle.Init.ClockPrescaler = 0x02;
OSPIPSRAMHandle.Init.SampleShifting = HAL_OSPI_SAMPLE_SHIFTING_NONE;
OSPIPSRAMHandle.Init.DelayHoldQuarterCycle = HAL_OSPI_DHQC_ENABLE;
OSPIPSRAMHandle.Init.ChipSelectBoundary = 4;
OSPIPSRAMHandle.Init.DelayBlockBypass = HAL_OSPI_DELAY_BLOCK_USED;
OSPIPSRAMHandle.Init.MaxTran = 0;

if (HAL_OSPIM_Config(&OSPIPSRAMHandle, &OSPIM_Cfg_Struct, HAL_OSPI_TIMEOUT_DEFAULT_VALUE) != HAL_OK)
{
return PSRAM_ERROR;
}

if (HAL_OSPI_Init(&OSPIPSRAMHandle) != HAL_OK) {
return PSRAM_ERROR;
}

sCommand.OperationType = HAL_OSPI_OPTYPE_COMMON_CFG;
sCommand.FlashId = HAL_OSPI_FLASH_ID_1;
sCommand.InstructionMode = HAL_OSPI_INSTRUCTION_8_LINES;
sCommand.InstructionSize = HAL_OSPI_INSTRUCTION_8_BITS;
sCommand.InstructionDtrMode = HAL_OSPI_INSTRUCTION_DTR_DISABLE;
sCommand.AddressMode = HAL_OSPI_ADDRESS_8_LINES;
sCommand.AddressSize = HAL_OSPI_ADDRESS_32_BITS;
sCommand.AddressDtrMode = HAL_OSPI_ADDRESS_DTR_ENABLE;
sCommand.AlternateBytesMode = HAL_OSPI_ALTERNATE_BYTES_NONE;
sCommand.DataMode = HAL_OSPI_DATA_8_LINES;
sCommand.DataDtrMode = HAL_OSPI_DATA_DTR_ENABLE;
sCommand.DQSMode = HAL_OSPI_DQS_ENABLE;
sCommand.SIOOMode = HAL_OSPI_SIOO_INST_EVERY_CMD;
sCommand.Instruction = READ_REG_CMD_SRAM;
sCommand.Address = 0;
sCommand.NbData = 2;
sCommand.DummyCycles = 5;

if (HAL_OSPI_Command(&OSPIPSRAMHandle, &sCommand, HAL_OSPI_TIMEOUT_DEFAULT_VALUE) != HAL_OK) {
return PSRAM_ERROR;
}

if (HAL_OSPI_Receive(&OSPIPSRAMHandle, reg, HAL_OSPI_TIMEOUT_DEFAULT_VALUE) != HAL_OK) {
return PSRAM_ERROR;
}

sCommand.Instruction = WRITE_REG_CMD_SRAM;
sCommand.DummyCycles = 0;
MODIFY_REG(reg[0], 0x03, 0x00);

if (HAL_OSPI_Command(&OSPIPSRAMHandle, &sCommand, HAL_OSPI_TIMEOUT_DEFAULT_VALUE) != HAL_OK) {
return PSRAM_ERROR;
}

if (HAL_OSPI_Transmit(&OSPIPSRAMHandle, reg, HAL_OSPI_TIMEOUT_DEFAULT_VALUE) != HAL_OK) {
return PSRAM_ERROR;
}

bsp_psram_initialized = 1;
}

return PSRAM_OK;
}

[KDJEM.1 · Accepted solution]

Hello @JKim.2,

Please use </> button to share your code. See this post.

Could you please check the maximum OCTOSPI frequency. I recommend you to look at Overall FAQs for QUADSPI/OCTOSPI/HSPI/XSPI and precisely "1.2. The maximum frequency" sub-section 

For STM32L4P5, the maximum OCTOSPI frequency is 92 MHz (not 120 MHz) that can be achieved with some conditions mentioned in the datasheet 6.3.29 OCTOSPI characteristics.

The Reference manual detailed the "Bits 7:0 PRESCALER[7:0]: Clock prescaler". This field must be between 0 and 255 and defines the scaler factor for generating the CLK based on the kernel clock (value + 1). 

If the clock prescaler is set to 0, this means the clock on the bus is 120MHz / 1 = 120MHz > 90MHz.

If the clock prescaler is set to 2, this means the clock on the bus is 120MHz / 3 = 40MHz < 90MHz.

Please see this post "Solved: Re: How to enable QSPI PSRAM as data memory - STMicroelectronics Community"

For STM32L4P5G-DK examples, you can refer to AN5050 precisely section "7 OCTOSPI application examples" and section "I. Octo-SPI PSRAM in Regular-command protocol example". These sections provides some typical OCTOSPI implementation examples with STM32L4P5xx/Q5xx products, and STM32CubeMX examples using the STM32L4P5G-DK Discovery kit for the STM32L4P5AGI6PU microcontroller.

Thank you.

Kaouthar