sh1106-spi invalid buffer alignment on 6.12 kernel

[gtrainavicius]

Describe the bug

Trying to load the DT overlay and module for sh1106 display (possibly other SPI displays are affected too), fails with invalid buffer alignment.

It is not necessary to have the actual display to be hooked up to reproduce the problem.

Doesn't happen on 6.6 kernel versions.

Steps to reproduce the behaviour

Execute:

sudo dtoverlay sh1106-spi,reset_pin=17,dc_pin=27

Device (s)

Raspberry Pi 5

System

patch@patchbox:~ $ cat /etc/rpi-issue
Raspberry Pi reference 2024-04-04
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 64e3efc023558a4d4634a702c467f513d5b2bca1, stage-patchbox
patch@patchbox:~ $ vcgencmd version
2025/03/19 13:41:26
Copyright (c) 2012 Broadcom
version cec1d3ae (release) (embedded)
patch@patchbox:~ $ uname -a
Linux patchbox 6.12.19-v8-16k+ #1865 SMP PREEMPT Wed Mar 19 13:48:20 GMT 2025 aarch64 GNU/Linux

Logs

6.12_error.log

6.6 success log for comparison:

6.6_success.log

Additional context

No response

[6by9]

Upstream have managed to configure two different kernel modules to have the same compatible string
https://elixir.bootlin.com/linux/v6.13.7/source/drivers/gpu/drm/solomon/ssd130x-spi.c#L113
https://elixir.bootlin.com/linux/v6.13.7/source/drivers/staging/fbtft/fb_sh1106.c#L173

Both are getting loaded, and it's the gpu/drm/solomon driver that is crashing.

If you want the deprecated fbtf version (which is what you appeared to have in 6.6), then create a file /etc/modprobe.d/blacklist-ssd130x-spi.conf with the contents blacklist ssd130x-spi.

[P33M]

The splat after that is from the AXI DMAC driver - presumably this error path hasn't been called before...

Also, I'm not entirely sure that the DMAC requires a word-aligned start address. It should only need naturally-aligned buffers with a length of integer multiples of SRC_WIDTH.

[6by9]

The solomon driver hasn't set a dma_mask, hence the

[   71.879798] ------------[ cut here ]------------
[   71.879804] WARNING: CPU: 1 PID: 1136 at kernel/dma/mapping.c:209 __dma_map_sg_attrs+0x164/0x178

[pelwell]

The solomon driver is passing in an odd address for the transfer, which is not very friendly. The problem with the error path is that axi_desc_put assumes that the LLIs have been allocated and calls dma_pool_free on them. I'll fix the latter.

[pelwell]

See #6734.

[pelwell]

Please close the issue if it has been resolved.