Hi,
I have a 26MHz SD card, the mmc driver with u-boot source had incorrectly setting it to 50MHz tran_speed and caused unreliable reading and writing on the SD card.
The variable "mmc->card_caps" had correctly described my SD card with value 0x05. i.e. 4 bit, MMC_MODE_HS, however, in function "static int mmc_startup(struct mmc *mmc)" with the blow section of code,
" If (mmc->card_caps & MMC_MODE_HS) mmc->tran_speed = 50000000; else mmc->tran_speed = 25000000; "
This section of codes wrongly set the "mmc->tran_speed" to 50MHz without considering there could be two types of high speed, that is 52M, and 26M. and then later on calling the "mmc_set_clock" function with 50MHZ.
Suggested change is given below:
" If (mmc->card_caps & MMC_MODE_HS) { If (mmc->card_caps & (MMC_MODE_HS_52MHz+MMC_MODE_DDR_52MHz)) mmc->tran_speed = 50000000; else mmc->tran_speed = 25000000; } "
Cheers, Damien