Increase RPi MMC/SD clock speed

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From: Ordinary Bit <ordinarybit_at_proton.me>
Date: Sun, 04 Feb 2024 10:43:22 UTC

Hi,

I'm checking my RPi MMC reader's default speed of 50 MHz if it can be increased? Because I'm verifying my SanDisk microSD card read/write performance. I want to know if there's a difference when I increase it to something like 80 MHz or 100 MHz speed.

root@sd-ultra:/mnt/boot # dmesg | grep mmc
...
mmc0: <MMC/SD bus> on sdhci_bcm0mmcsd0: 64GB <SDHC SC64G 8.0 SN 4C1E9678 MFG 10/2023 by 3 SD> at mmc0 50.0MHz/4bit/65535-block

So, I added the default /boot/msdos/config.txt line of dtoverlay=mmc to dtoverlay=mmc,overclock_50=80 and then reboot my RPi but in the dmesg it's still the same 50 MHz as shown above.

Any idea if this is possible or did I added the parameter correctly?

TY,
Ordinary Bit

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