[Letux-kernel] jz4730

Paul Boddie paul at boddie.org.uk
Sun Jul 5 16:17:19 CEST 2020

On Tuesday, 30 June 2020 08:04:09 CEST H. Nikolaus Schaller wrote:
> Well, I wasn't able to pick or compile your latest code - and worse, the
> CI20 doesn't boot any more with v5.8-rc1 or letux-5.8-rc1 (even without
> your latest patches).

Replying to this again specifically, I found that the DRM/HDMI patches based 
on letux-5.8-rc3 will not yield a bootable kernel, but by disabling SMP in the 
configuration it would boot. So that is probably a significant factor.

Unfortunately, I did not manage to get a usable signal via HDMI ("Input not 
supported"), but the DRM driver is operational. One strange complication I now 
get when I unplug the HDMI cable (to get my monitor to switch back to the VGA 
input, since the menu won't respond) is this kernel panic:

CPU 0 Unable to handle kernel paging request at virtual address 00000030,
epc == c025ee10, ra == c022fc08

ingenic_drm_crtc_atomic_flush+0x8c/0x3ac [ingenic_drm]
drm_atomic_helper_commit_planes+0x254/0x25c [drm_kms_helper]
drm_atomic_helper_commit_tail+0x44/0xb0 [drm_kms_helper]
commit_tail+0x1f0/0x1f8 [drm_kms_helper]
drm_atomic_helper_commit+0x17c/0x184 [drm_kms_helper]
drm_client_modeset_commit_atomic+0xdc/0x2a8 [drm]
drm_client_modeset_commit_locked+0x6c/0x1b8 [drm]
drm_client_modeset_commit+0x44/0x74 [drm]
__drm_fb_helper_restore_fbdev_mode_unlocked+0x74/0xd8 [drm_kms_helper]
drm_fb_helper_set_par+0x74/0x84 [drm_kms_helper]
drm_fb_helper_hotplug_event+0x170/0x190 [drm_kms_helper]
drm_kms_helper_hotplug_event+0x34/0x50 [drm_kms_helper]
drm_helper_hpd_irq_event+0xcc/0x1a0 [drm_kms_helper]
dw_hdmi_irq+0x12c/0x178 [dw_hdmi]

So, upon receiving the hotplug event (in dw_hdmi_irq), the attempt to 
configure the LCD controller fails (in ingenic_drm_crtc_atomic_flush) due to 
an inappropriate access.

One positive observation is that shutdown appears to power the device off. One 
negative observation is that networking doesn't seem to work any more, 
although this might be a user space incompatibility.


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