DE1-SOC: Baremetal SDCARD reading performance

Hi,

I try to improve our SDCard reading performance.

I have tested the speed of sdcard that we will use on our project, and windows can write a big file to it with 10MB/sec and read back with around 20MB/sec.

When I plug same card into DE1-SOC board, I can read only 1.58 MB/sec. And this is after enabling cache, mmu and use high speed setting for MMC interface.

Here is my MMU and MMC settings:

void mmu_init(void)
{
	uint32_t *ttb1 = NULL;
	/* Populate the page table with sections (1 MiB regions). */
	ALT_MMU_MEM_REGION_t regions = 
	{
		/* Memory area: 1 GiB */
		{
			.va = (void *)0x00000000,
			.pa = (void *)0x00000000,
			.size = 0x40000000,
			.access = ALT_MMU_AP_FULL_ACCESS,
			.attributes = ALT_MMU_ATTR_DEVICE_NS, // ALT_MMU_ATTR_WBA causes SD card fail at reading, why??
			.shareable = ALT_MMU_TTB_S_NON_SHAREABLE,
			.execute = ALT_MMU_TTB_XN_DISABLE,
			.security = ALT_MMU_TTB_NS_SECURE
		},
		/* Device area: Everything else */
		{
			.va = (void *)0x40000000,
			.pa = (void *)0x40000000,
			.size = 0xc0000000,
			.access = ALT_MMU_AP_FULL_ACCESS,
			.attributes = ALT_MMU_ATTR_DEVICE_NS,
			.shareable = ALT_MMU_TTB_S_NON_SHAREABLE,
			.execute = ALT_MMU_TTB_XN_ENABLE,
			.security = ALT_MMU_TTB_NS_SECURE
		}
	};
	alt_mmu_init();
	alt_mmu_va_space_storage_required(regions, sizeof(regions)/sizeof(regions));
	alt_mmu_va_space_create(&ttb1, regions, sizeof(regions)/sizeof(regions), alt_pt_alloc, alt_pt_storage);
	alt_mmu_va_space_enable(ttb1);
}
void init_mmc(void)
{
    ALT_STATUS_CODE status = ALT_E_SUCCESS;
    ALT_SDMMC_CARD_MISC_t card_misc_cfg;
    print_debug("MMC Initialization.\n");
	alt_globaltmr_int_is_enabled();
	alt_sdmmc_init();
	alt_sdmmc_card_pwr_on();
	alt_sdmmc_card_identify(&Card_Info); // Card_Info.card_type == ALT_SDMMC_CARD_TYPE_SDHC
	alt_sdmmc_card_bus_width_set(&Card_Info, ALT_SDMMC_BUS_WIDTH_4);
	alt_sdmmc_fifo_param_set((ALT_SDMMC_FIFO_NUM_ENTRIES >> 3) - 1, (ALT_SDMMC_FIFO_NUM_ENTRIES >> 3), ALT_SDMMC_MULT_TRANS_TXMSIZE1);
	alt_sdmmc_card_misc_get(&card_misc_cfg);    
    alt_sdmmc_dma_enable();
	alt_sdmmc_card_speed_set(&Card_Info, (Card_Info.high_speed ? 2 : 1) * Card_Info.xfer_speed); // switch to high speed
}

What can I do to improve sdcard reading performance? (windows reads 13 times faster)

Thanks.