Jetson/FAQ/BSP/sdcard

How to limit speed if board has bad signal quality?

Kernel descriptions:
$kernel/kernel-4.9/Documentation/devicetree/bindings/mmc/sdhci-tegra.txt

  - uhs-mask: Specify modes that are masked for the device                  
    Mask HS200 mode: 0x20                                                       
    Mask HS400 mode: 0x40                                                       
    Mask SDR104 mode: 0x10                                                      
    Mask SDR50 mode: 0x4                                                        
    Mask DDR50 mode: 0x8                                                        
    Mask SDR25 mode: 0x2

Source Code:
tegra_sdhci_mask_host_caps() from $kernel/kernel/kernel-4.9/drivers/mmc/host/sdhci-tegra.c

Instance:
If SDR104 can't supported by hardware limitation, uhs-mask should set to:
0x70 : which means support "SD_HS|DDR50|SDR50|SDR25|SDR12"
or
0x78 : which means support "SD_HS|SDR50|SDR25|SDR12"