FW: eMMC AMD platform

[Amartya, Shreyank]

Hi,

I have an AMD eMMC 5.0 controller connected to an eMMC device.
I recently got around to enabling HS400 mode but the performance is still same what I was getting in HS200 mode.
Is there a way to verify the HS400 mode is active?

Patch for enabling HS400: https://reviews.freebsd.org/D17644

In order to enable the HS400 mode I had to clear the Sampling clock select bit (Host control 2 register) and then set it later (as part of the patch).
Now, I suspect that this led to reset of the tuning circuit and that even though HS400 mode is enabled, since it is not tuned, I do not see increase in performance. Could that be a possibility?

There is a similar patch for linux and I've tried it, it works on my board with HS400 mode (~200 MB/s), measured using iozone.
Linux patch: https://patchwork.kernel.org/patch/10086747/

Thanks
Shreyank Amartya