[xu4] dmesg spammed once a second with mmc0 bus speed messages

Test and fix the Kernel 4.14 features
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kidovate
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[xu4] dmesg spammed once a second with mmc0 bus speed messages

Post by kidovate »

Posted as an issue here: https://github.com/hardkernel/linux/issues/401

Against a Odroid XU4q running 4.14.180-176 tag (current HEAD of odroidxu4-4.14.y) -

Dmesg is spammed with 4 messages, once a second. Definitely not OK.

```
[ 3069.842645] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 400000Hz, actual 396825HZ div = 63)
[ 3069.898673] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 300000Hz, actual 297619HZ div = 84)
[ 3069.954564] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 200000Hz, actual 200000HZ div = 125)
[ 3070.010645] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 100000Hz, actual 100000HZ div = 250)
[ 3070.490613] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 400000Hz, actual 396825HZ div = 63)
[ 3070.550598] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 300000Hz, actual 297619HZ div = 84)
[ 3070.606600] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 200000Hz, actual 200000HZ div = 125)
[ 3070.662552] mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 100000Hz, actual 100000HZ div = 250)
```

It looks like it's checking for all of the possible bus speeds on the mmc once a second, possibly to detect if it has been hotplugged / connected (it's not). However, this log message shouldn't be spammed so much.

I will put a small patch against my own copy of Linux which removes the message, but this needs a more permanent fix.

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Re: [xu4] dmesg spammed once a second with mmc0 bus speed messages

Post by kidovate »

Looks like this could be a fix from upstream: https://patchwork.kernel.org/patch/9344483/

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Re: [xu4] dmesg spammed once a second with mmc0 bus speed messages

Post by odroid »

Right. The useless eMMC hot-plug detection logic caused the problem.
The problem occurs only when the SD card is used as a boot media without eMMC module.

Run the following commands with super-user and it will fix the issue.

Code: Select all

apt install device-tree-compiler
fdtput /media/boot/exynos5422-odroidxu4.dtb /soc/mmc@12200000/ non-removable
reboot

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Re: [xu4] dmesg spammed once a second with mmc0 bus speed messages

Post by kidovate »

@odroid I'm using Skiff / Buildroot https://github.com/paralin/SkiffOS

export SKIFF_CONFIG=odroid/xu4,skiff/core
make configure compile
sudo bash
export ODROID_SD=/dev/sdc
make cmd/odroid/common/format
make cmd/odroid/common/install

I will integrate this fixup with Skiff with a kernel patch to tweak the dts.

Thanks!
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odroid (Tue Sep 01, 2020 11:13 am)

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Re: [xu4] dmesg spammed once a second with mmc0 bus speed messages

Post by kidovate »

@odroid - The patch I added is here:

https://github.com/paralin/SkiffOS/comm ... 5508da9R23

Added non-removable to the DTS. Hopefully this works as anticipated. Probably, the card detect delay can also be dropped.
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