Hi Bjorn,
On 08.01.2025 01:45, Bjorn Helgaas wrote:
On Wed, Jan 08, 2025 at 01:13:41AM +0200, Sergey Ryazanov wrote:
On 05.01.2025 19:39, Maciej S. Szmigiero wrote:
Currently, the driver is seriously broken with respect to the
hibernation (S4): after image restore the device is back into
IPC_MEM_EXEC_STAGE_BOOT (which AFAIK means bootloader stage) and needs
full re-launch of the rest of its firmware, but the driver restore
handler treats the device as merely sleeping and just sends it a
wake-up command.
This wake-up command times out but device nodes (/dev/wwan*) remain
accessible.
However attempting to use them causes the bootloader to crash and
enter IPC_MEM_EXEC_STAGE_CD_READY stage (which apparently means "a crash
dump is ready").
It seems that the device cannot be re-initialized from this crashed
stage without toggling some reset pin (on my test platform that's
apparently what the device _RST ACPI method does).
While it would theoretically be possible to rewrite the driver to tear
down the whole MUX / IPC layers on hibernation (so the bootloader does
not crash from improper access) and then re-launch the device on
restore this would require significant refactoring of the driver
(believe me, I've tried), since there are quite a few assumptions
hard-coded in the driver about the device never being partially
de-initialized (like channels other than devlink cannot be closed,
for example).
Probably this would also need some programming guide for this hardware.
Considering that the driver seems orphaned [1] and other people are
hitting this issue too [2] fix it by simply unbinding the PCI driver
before hibernation and re-binding it after restore, much like
USB_QUIRK_RESET_RESUME does for USB devices that exhibit a similar
problem.
Tested on XMM7360 in HP EliteBook 855 G7 both with s2idle (which uses
the existing suspend / resume handlers) and S4 (which uses the new code).
[1]: https://lore.kernel.org/all/c248f0b4-2114-4c61-905f-466a786bdebb@xxxxxxxxxxxxx/
[2]:
https://github.com/xmm7360/xmm7360-pci/issues/211#issuecomment-1804139413
Signed-off-by: Maciej S. Szmigiero <mail@xxxxxxxxxxxxxxxxxxxxx>
Generally looks good to me. Lets wait for approval from PCI maintainers to
be sure that there no unexpected side effects.
I have nothing useful to contribute here. Seems like kind of a mess.
But Intel claims to maintain this, so it would be nice if they would
step up and make this work nicely.
Suddenly, Intel lost their interest in the modems market and, as Maciej
mentioned, the driver was abandon for a quite time now. The author no
more works for Intel. You will see the bounce.
Bjorn, could you suggest how to deal easily with the device that is
incapable to seamlessly recover from hibernation? I am totally hopeless
regarding the PM topic. Or is the deep driver rework the only option?
--
Sergey
