How do I check the SDIO clock frequency on an imx8qm board? Is there a way to change it?

[Sanjay_SAE]

Hi I am trying to figure out what SD clock frequency is on the imx8qm.

Is there a device tree entry where I can see the SDIO clock frequency.

I am running an android 10 Image.

Is there a similar entry for linux as well?

[fmonte]

Does

     cat /sys/kernel/debug/mmcX/ios

help you?

[Sanjay_SAE]

@fmonte 

ls -l /sys/kernel/
total 0
drwxr-xr-x 2 root root 0 2020-12-17 17:12 cgroup
dr-xr-xr-x 2 root root 0 2020-12-17 17:12 config
-r--r--r-- 1 root root 4096 2020-12-17 17:12 fscaps
drwxr-xr-x 2 root root 0 2020-12-17 17:12 iommu_groups
drwxr-xr-x 2 root root 0 2020-12-17 17:12 ion
drwxr-xr-x 222 root root 0 2020-12-17 17:12 irq
-r--r--r-- 1 root root 4096 2020-12-17 17:12 kexec_crash_loaded
-rw-r--r-- 1 root root 4096 2020-12-17 17:12 kexec_crash_size
-r--r--r-- 1 root root 4096 2020-12-17 17:12 kexec_loaded
-r--r--r-- 1 root root 3437380 2020-12-17 17:12 kheaders.tar.xz
drwxr-xr-x 5 root root 0 2020-12-17 17:10 mm
-r--r--r-- 1 root root 60 2020-12-17 17:12 notes
-rw-r--r-- 1 root root 4096 2020-12-17 17:12 profiling
-rw-r--r-- 1 root root 4096 2020-12-17 17:12 rcu_expedited
-rw-r--r-- 1 root root 4096 2020-12-17 17:12 rcu_normal
dr-xr-xr-x 2 root root 0 2020-12-17 17:12 security
drwxr-xr-x 139 root root 0 2020-12-17 17:12 slab
drwxr-xr-x 2 root root 0 2020-12-17 17:12 software_nodes
dr-xr-xr-x 2 root root 0 2020-12-17 17:12 tracing
-r--r--r-- 1 root root 4096 2020-12-17 17:12 uevent_seqnum
-r--r--r-- 1 root root 4096 2020-12-17 17:12 vmcoreinfo
drwxr-xr-x 2 root root 0 2020-12-17 17:12 wakeup_reasons

evk_8mn:/ # ls -l /sys/kernel/de*
ls: /sys/kernel/de*: No such file or directory

evk_8mn:/ # ls -l /sys/kernel/debug
ls: /sys/kernel/debug: No such file or directory

[igorpadykov · Accepted solution]

Hi Sanjay

>Is there a device tree entry where I can see the SDIO clock frequency.

SDIO clock frequency is selected by MMC/SD/SDIO driver automatically, so I am afraid

there is no way to see it in device tree. Driver reads device configuration register

containing device capability, like supported operating frequencies, voltages, e.t.c.

Then chooses suitable values.

To see clocks one can run unit test :

https://source.codeaurora.org/external/imx/imx-test/tree/test/mxc_clock_test?h=imx_5.4.70_2.3.0

Best regards
igor