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Need to change the usdhc clock frequency in Linux 4.1 BSP

Question asked by Asmita Amonkar on Nov 17, 2016


Linux BSP version : 4.1
CPU : imx6 quad
Purpose: To test SD card with different frequency for e.g. 48 Mhz, want to change the usdhc clock frequency. 


As per datasheet following steps are required to change the usdhc clock:

1. Change PLL2_PFD2 clock frequency:
a) Change the CCM_ANALOG_PFD_528n Register for PFD2_FRAC value ( PFD2_FRAC is divisor for PLL2_PFD2 clock)
PLL2_PFD2 clock = 528*18/PFD2_FRAC
2. Set the CCM_CSCMR1 register (Bit 16,17,18,19) for deriving clock from "derive clock from 396M PFD" option ( This option is already set in the BSP )
3. Set the CSCDR1 register for usdhcx_podf [2:0] bits.

Need help in knowing which files of the BSP can be changed.