ddrbin-switch-freq.sh

#!/bin/bash

TARGET=$1
NEW_FREQUENCY=$2

function print_usage() {

    APP=$(basename $0)

    echo -e "Usage:"
    echo -e "$APP <target> <frequency>"
    echo
    echo -e "<target>\tthe target file or the block device where ddrbin is contained"
    echo -e "<frequency>\tchosen frequency, in MHz, to set"
    echo
    echo -e "Examples:"
    echo
    echo -e "./$APP block.bin 660"
    echo -e "./$APP /dev/mmcblk0 660"
    echo

}

echo -e "Rockchip rk3318/rk3328 ddrbin frequency switcher"
echo
echo -e "DISCLAIMER!!! Use this script at your own risk, proper or improper use may"
echo -e "prevent existing systems to boot and could require hardware manipulation"
echo -e "to restore functionalty. Do not use it if you are not prepared for consequences"
echo

if [[ -z "$TARGET" ]]; then
    print_usage
    exit 0
fi

if [[ -z "$NEW_FREQUENCY" ]]; then
    print_usage
    exit 0
fi

if [[ "$NEW_FREQUENCY" -lt 330 || "$NEW_FREQUENCY" -gt 800 ]]; then
    echo "Invalid frequency value, valid range is 330 - 800"
    exit 0
fi

# Create a tempfile that we will use for our operations
TEMPFILE=$(mktemp)

ERROR=$(dd if="$TARGET" of="$TEMPFILE" bs=64k count=1 2>&1 1>/dev/null)

if [[ $? -ne 0 ]]; then
    echo "error when accessing $TARGET: $ERROR"
    exit 1
fi

# Find the offset for the given signature
OFFSET=$(od --endian=big -A o -w4 -tx4 "$TEMPFILE" | grep "60e31621" | cut -d " " -f 1)

if [[ -z "$OFFSET" ]]; then
    echo "could not proceed: unable to find signature in the target file/device"
    exit 1
fi

# Our target values are 12 bytes before the signature
OFFSET=$(($OFFSET - 12))

# Extract the frequency numbers from the target, we should get 6 strings all of
# them with the identical frequency value
FREQ_VALUES=$(od -s -A n -j $OFFSET -N 12 $TEMPFILE | tr -s " ")

if [[ -z "FREQ_VALUES" ]]; then
    echo "could not proceed: unable to find valid frequency values in target"
    exit 1
fi

# Use read to convert the frequency values string into an array, we will
# also check if all the items in the array have the same values
read -a FREQ_ARRAY <<< $FREQ_VALUES

if [[ ${#FREQ_ARRAY[@]} -ne 6 ]]; then
    echo "could not proceed: the frequency array does not contains the expected 6 elements"
    exit 1
fi

CHECK_REF_VALUE=${FREQ_ARRAY[0]}
for CHECK_VALUE in ${FREQ_ARRAY}; do
    if [[ "$CHECK_REF_VALUE" -ne "$CHECK_VALUE" ]]; then
        echo "could not proceed: the frequency values in the array do not match"
        exit 1
    fi
done

echo "Current frequency in $TARGET: $CHECK_REF_VALUE MHz"
echo "Changing with $NEW_FREQUENCY MHz"

# All checks are ok, now proceed to write the values to the temporary file and then
# copy the temporary file over the target
LOW=$(($NEW_FREQUENCY % 256))
HIGH=$(($NEW_FREQUENCY / 256))
for idx in {1..6}; do
    # First write low byte (double printf is necessary, sigh :( )
    printf \\$(printf '%03o' $LOW) | dd of="$TEMPFILE" bs=1 seek=$OFFSET count=1 conv=notrunc 2>/dev/null
    OFFSET=$(($OFFSET + 1))

    # Then write high byte
    printf \\$(printf '%03o' $HIGH) | dd of="$TEMPFILE" bs=1 seek=$OFFSET count=1 conv=notrunc 2>/dev/null
    OFFSET=$(($OFFSET + 1))
done

if [[ $? -ne 0 ]]; then
    echo "an error occurred writing new frequency to temporary file"
    exit 1
fi

# Finally substitute the binary part into the target with the temporary file
ERROR=$(dd if="$TEMPFILE" of="$TARGET" bs=64k count=1 conv=notrunc 2>&1 1>/dev/null)

if [[ $? -ne 0 ]]; then
    echo "an error occurred committing the new frequency to target file: $ERROR"
    exit 1
fi

# Remove the temporary file
rm "$TEMPFILE"

echo "done."