[regression] HDMI breakage just before poweroff

[Robin Murphy]

On 03/05/18 04:51, JeffyChen wrote:
> Hi Vincente,
> 
> Thanks for your mail.
> 
> On 05/03/2018 03:36 AM, Vicente Bergas wrote:
>> Hello,
>> on rk3399-sapphire there is a missing feature: the poweroff command is
>> unable to poweroff the system and the display stays on.
>> When the system is halted, power needs to be removed manually.
> according to the dtsi, the rk3399-sapphire is using rk808 pimc right?
> 
> i think the power off flow would be:
> 1/ rk808 set the pm_power_off callback:
> drivers/mfd/rk808.c
>          switch (rk808->variant) {
>          case RK805_ID:
>      ...
>                  pm_pwroff_fn = rk805_device_shutdown;
>      ...
> 
>          pm_off = of_property_read_bool(np,
>                                  "rockchip,system-power-controller");
>          if (pm_off && !pm_power_off) {
>                  rk808_i2c_client = client;
>                  pm_power_off = pm_pwroff_fn;
>          }
> 
> 2/ the poweroff command would call kernel_power_off:
> kernel/reboot.c:
> void kernel_power_off(void)
> {
> ...
>          machine_power_off();
> }
> 
> 3/ arm64's machine_power_off() would call pm_power_off to let rk808 
> cutoff the power.

Doesn't PSCI's pm_power_off take precedence, though? This sounds similar 
to what my RK3328 does - I looked into that briefly a while ago, and 
from what I remember it appeared that the firmware SYSTEM_OFF handler 
tries to turn off the PMIC by driving the SLEEP pin, but the kernel 
driver never actually configures it into the correct mode for that to 
work. Thus the box just ends up spinning in the firmware until you pull 
the plug manually.

>> With Linux kernel 4.16, when reaching the halted state, the HDMI console
>> shows the last messages before halting.
> if it ends up halted, maybe something wrong during setup the pm_power_off?
> kernel/reboot.c:
>          /* Instead of trying to make the power_off code look like
>           * halt when pm_power_off is not set do it the easy way.
>           */
>          if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
>                  cmd = LINUX_REBOOT_CMD_HALT;
> 
>>
>> With 4.17.0-rc3, when reaching the halted state, the HDMI console
>> shows colorful static noise.
>>
> we've added a shutdown() to the iommu driver:
> https://patchwork.kernel.org/patch/10230817/
> 
> any chance related?

For sure - the IOMMU shutdown disables paging, so if the VOP is still 
scanning out then that will result in whatever IOVAs it was using now 
going straight out onto the bus as physical addresses. Between the 
RK3399 memory map and the way the IOVA allocator works, that probably 
means it's reading from all over the peripherals region, which, er, 
isn't ideal.

Robin.