Xenial/raspi2 and RaspberryPi3A+: video not working

[Paolo Pisati]

Video is not working on the RaspberryPi3A+, and in dmesg there's this:

ubuntu@raspi3:~$ dmesg | grep cma
[ 0.000000] cma: Region at 0x10000000 defined on low/high memory boundary (0x1c000000)
[ 0.000000] cma: Failed to reserve 256 MiB
[ 0.000000] Kernel command line: 8250.nr_uarts=1 cma=256M@256M bcm2708_fb.fbwidth=1680 bcm2708_fb.fbheight=1050 bcm2708_fb.fbswap=1 dma.dmachans=0x7f35 bcm2709.boardrev=0x9020e0 bcm2709.serial=0x976d0cc5 bcm2709.uart_clock=48000000 bcm2709.disk_led_gpio=29 bcm2709.disk_led_active_low=0 vc_mem.mem_base=0x1ec00000 vc_mem.mem_size=0x20000000 dwc_otg.lpm_enable=0 console=ttyS0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
[ 0.000000] Memory: 438856K/458752K available (8816K kernel code, 550K rwdata, 2688K rodata, 1024K init, 809K bss, 19896K reserved, 0K cma-reserved)
[ 1.209261] vc-cma: Videocore CMA driver
[ 1.213283] vc-cma: vc_cma_base = 0x00000000
[ 1.218091] vc-cma: vc_cma_size = 0x00000000 (0 MiB)
[ 1.223604] vc-cma: vc_cma_initial = 0x00000000 (0 MiB)

it tries to allocate 256M for CMA and fail, and that has a cascade effect on the drm driver (that fails to init) and as such the video is not working.

One easy workaround i found is to reduce the CMA size from 256M to 128M on the bootargs:

[ 0.000000] cma: Reserved 128 MiB at 0x10000000
[ 0.000000] Kernel command line: 8250.nr_uarts=1 cma=128M@256M bcm2708_fb.fbwidth=1680 bcm2708_fb.fbheight=1050 bcm2708_fb.fbswap=1 dma.dmachans=0x7f35 bcm2709.boardrev=0x9020e0 bcm2709.serial=0x976d0cc5 bcm2709.uart_clock=48000000 bcm2709.disk_led_gpio=29 bcm2709.disk_led_active_low=0 vc_mem.mem_base=0x1ec00000 vc_mem.mem_size=0x20000000 dwc_otg.lpm_enable=0 console=ttyS0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
[ 0.000000] Memory: 307528K/458752K available (8816K kernel code, 550K rwdata, 2688K rodata, 1024K init, 809K bss, 20152K reserved, 131072K cma-reserved)
[ 1.207110] vc-cma: Videocore CMA driver
[ 1.211131] vc-cma: vc_cma_base = 0x00000000
[ 1.215939] vc-cma: vc_cma_size = 0x00000000 (0 MiB)
[ 1.221454] vc-cma: vc_cma_initial = 0x00000000 (0 MiB)

this way the video works again.

[Paolo Pisati (p-pisati)]

Ok so, it's official that with 512MB you have to downgrade the CMA to 128MB:

https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial/tree/arch/arm/boot/dts/overlays/README?h=raspi2#n1317

so the dtoverlay line should go from:

dtoverlay=vc4-kms-v3d

to:

dtoverlay=vc4-kms-v3d,cma-128

and with this setup, the board works fine.

Still, i agree that it should fail gracefully if the wrong cma size is specified - i fixed the OOPS on boot here: https://bugs.launchpad.net/ubuntu/+source/linux-raspi2/+bug/1805117 but once the board is running, we later hit another problem:

[ 360.269693] INFO: task kworker/1:2:101 blocked for more than 120 seconds.
[ 360.276605] Not tainted 4.4.0-1101-raspi2 #109~vc4dbg5
[ 360.282360] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 360.290316] kworker/1:2 D 80895384 0 101 2 0x00000000
[ 360.290338] Workqueue: events dbs_timer
[ 360.290356] [<80895384>] (__schedule) from [<8089589c>] (schedule+0x50/0xa8)
[ 360.290366] [<8089589c>] (schedule) from [<80898c80>] (schedule_timeout+0x218/0x2a0)
[ 360.290376] [<80898c80>] (schedule_timeout) from [<80896668>] (wait_for_common+0xc8/0x1a0)
[ 360.290384] [<80896668>] (wait_for_common) from [<80896760>] (wait_for_completion+0x20/0x24)
[ 360.290395] [<80896760>] (wait_for_completion) from [<8073f0d4>] (rpi_firmware_transaction+0x78/0xd0)
[ 360.290406] [<8073f0d4>] (rpi_firmware_transaction) from [<8073f20c>] (rpi_firmware_property_list+0xe0/0x24c)
[ 360.290415] [<8073f20c>] (rpi_firmware_property_list) from [<8073f3ec>] (rpi_firmware_property+0x74/0xec)
[ 360.290425] [<8073f3ec>] (rpi_firmware_property) from [<80712c80>] (bcm2835_cpufreq_clock_property.constprop.1+0x58/0x80)
[ 360.290437] [<80712c80>] (bcm2835_cpufreq_clock_property.constprop.1) from [<80712d00>] (bcm2835_cpufreq_driver_target_index+0x58/0xdc)
[ 360.290446] [<80712d00>] (bcm2835_cpufreq_driver_target_index) from [<8070bb94>] (__cpufreq_driver_target+0x234/0x3b4)
[ 360.290456] [<8070bb94>] (__cpufreq_driver_target) from [<807101e8>] (od_check_cpu+0xdc/0xe0)
[ 360.290465] [<807101e8>] (od_check_cpu) from [<80712170>] (dbs_check_cpu+0x1d0/0x22c)
[ 360.290474] [<80712170>] (dbs_check_cpu) from [<8071045c>] (od_dbs_timer+0x60/0xf4)
[ 360.290483] [<8071045c>] (od_dbs_timer) from [<807124f4>] (dbs_timer+0x15c/0x1a8)
[ 360.290494] [<807124f4>] (dbs_timer) from [<80140ed0>] (process_one_work+0x160/0x50c)
[ 360.290504] [<80140ed0>] (process_one_work) from [<801412dc>] (worker_thread+0x60/0x5d0)
[ 360.290513] [<801412dc>] (worker_thread) from [<80147808>] (kthread+0x118/0x130)
[ 360.290525] [<80147808>] (kthread) from [<80108ebc>] (ret_from_fork+0x14/0x38)
[ 360.290533] INFO: task kworker/3:2:135 blocked for more than 120 seconds.
[ 360.297430] Not tainted 4.4.0-1101-raspi2 #109~vc4dbg5
[ 360.303176] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 360.311129] kworker/3:2 D 80895384 0 135 2 0x00000000
[ 360.311141] Workqueue: events dbs_timer
[ 360.311151] [<80895384>] (__schedule) from [<8089589c>] (schedule+0x50/0xa8)
[ 360.311160] [<8089589c>] (schedule) from [<80895c78>] (sch...

[Paolo Pisati (p-pisati)]

Here is a pastebin of the above dmesg without the line wrap: http://paste.ubuntu.com/p/mGfz3St6c9/

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.