Opening a new issue as this is on different lines, brought here from: Slow SD card access speed (read+write) with Jetson Nano production module .
As discussed in the above topic, there was an issue with a slow access to SD card. The issue was solved by the patch mentioned there. However, a strange behaviour was noticed:
When I do a soft reboot (
sudo reboot), and then check the ios using:
cat /sys/kernel/debug/mmc1/ios, I get the following output:
clock: 50000000 Hz vdd: 21 (3.3 ~ 3.4 V) bus mode: 2 (push-pull) chip select: 0 (don't care) power mode: 2 (on) bus width: 2 (4 bits) timing spec: 2 (sd high-speed) signal voltage: 0 (3.30 V) driver type: 0 (driver type B)
But I have changed the dtb (as mentioned in the forum to which the link is provided above) already before flashing, so this should not be the case. Instead what I should get as an output is the following, which I also get with a hard reboot (power off+on).
clock: 204000000 Hz vdd: 21 (3.3 ~ 3.4 V) bus mode: 2 (push-pull) chip select: 0 (don't care) power mode: 2 (on) bus width: 2 (4 bits) timing spec: 6 (sd uhs SDR104) signal voltage: 1 (1.80 V) driver type: 0 (driver type B)
For the soft reboot case, I also observe that the SD card access speeds are actually slower 4 times (like 23 MBps vs 85 MBps on a hard reboot), when tested with the gnome-disks benchmarking utility.
Please note that this issue is not the same as mentioned here: how to modify the dts file for jetson nano board.
I always see my dtb changes, it is just that on soft reboot, the speed of SD card is slower (see the ios output above), and on hard reboot, the speed is as desired (again, the ios output above). I can always get to the desired behaviour with a hard reboot, but there are some cases where I have to do a soft reboot during operation while at customer’s end and many a times a hard reboot is not feasible. It is as though the SD card access speed mode detected by the kernel is different (only high speed mode instead of ultra high speed mode) for a soft reboot case. The SD card is of course the same in all cases. In the first link I provided, you can see the history of changes made to enable SD card, improve boot time with SD card in place, improve speed of access to SD card, etc.