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Can't boot non device-tree capable kernel on RPi4 #1175

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9pi opened this issue Jul 5, 2019 · 7 comments
Closed

Can't boot non device-tree capable kernel on RPi4 #1175

9pi opened this issue Jul 5, 2019 · 7 comments

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@9pi
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9pi commented Jul 5, 2019

The Plan 9 kernel uses ATAGs, not device tree, and successfully boots on RPi3 using the latest start.elf. On RPi4 with start4.elf, it boots and R2 is pointing to a flattened device tree. According to documentation, I should be able to specify device_tree= in config.txt, or add a trailer with DTOK=n or DTOK tag missing, to boot with ATAGs instead. But when I do either or both of these, the kernel does not boot at all.

Does start4.elf still support non device-tree capable kernels?
@9pi
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9pi commented Jul 5, 2019

It seems also that start4.elf won't boot a kernel binary file whose size isn't a multiple of 4 bytes, when the same file boots fine on RPi3. Luckily that's easy to work around!

@pelwell
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pelwell commented Jul 5, 2019

The very latest build (available as a download from this repo and via rpi-update) should work for non-Device Tree uses again. The problem was caused by the stubs exceeding 256 bytes, which is where the ATAGs are created - apparently some old/bare-metal projects expect them to be there.

I wasn't aware of the multiple-of-4 restriction, and off the top of my head I can't think of a reason why Pi4 would be different from Pi3 in this regard.

@9pi
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9pi commented Jul 5, 2019

Yes, it now works again. Thank you!

@9pi 9pi closed this as completed Jul 5, 2019
@pelwell
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pelwell commented Jul 5, 2019

Cool. If you have a non-multiple-of-4 "kernel" around to try with the new firmware I'd be grateful for the data point.

@9pi
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9pi commented Jul 5, 2019

If you have a non-multiple-of-4 "kernel" around

Easily done: echo >>/boot/kernel7l.img
Result won't boot, even with the new firmware.

@pelwell
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pelwell commented Jul 5, 2019

Cheers - it shouldn't be hard to fix.

popcornmix added a commit that referenced this issue Jul 8, 2019
@popcornmix
firmware: AWB: Fix usage for IR operation
549140c 
See: #1167

firmware: arm_loader: Support CLOCK_EMMC2 from GET_CLOCK_RATE
See: #1179

firmware: arm_loader: Force word alignment for the DTB
See: #1175

firmware: clock_2711: don't set reserved values for KA in PLL KAIP registers

firmware: Assorted minor fixes for tvservice -o
popcornmix added a commit to Hexxeh/rpi-firmware that referenced this issue Jul 8, 2019
@popcornmix
firmware: AWB: Fix usage for IR operation
9d7406f 
See: raspberrypi/firmware#1167

firmware: arm_loader: Support CLOCK_EMMC2 from GET_CLOCK_RATE
See: raspberrypi/firmware#1179

firmware: arm_loader: Force word alignment for the DTB
See: raspberrypi/firmware#1175

firmware: clock_2711: don't set reserved values for KA in PLL KAIP registers

firmware: Assorted minor fixes for tvservice -o
@popcornmix
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popcornmix commented Jul 8, 2019 •
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Latest rpi-update firmware should have a fix for non aligned "kernel" sizes. Please test.

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3 participants
@popcornmix @9pi @pelwell