[PATCH v7 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

[Kalle Valo]

Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org> writes:

> On Tue, Mar 05, 2024 at 10:13:18AM +0800, Baochen Qiang wrote:
>
>> ath11k fails to resume:
>> 
>> ath11k_pci 0000:06:00.0: timeout while waiting for restart complete
>> 
>> This happens because when calling mhi_sync_power_up() the MHI subsystem
>> eventually calls device_add() from mhi_create_devices() but the device
>> creation is deferred:
>> 
>> mhi mhi0_IPCR: Driver qcom_mhi_qrtr force probe deferral
>> 
>> The reason for deferring device creation is explained in dpm_prepare():
>> 
>>         /*
>>          * It is unsafe if probing of devices will happen during suspend or
>>          * hibernation and system behavior will be unpredictable in this case.
>>          * So, let's prohibit device's probing here and defer their probes
>>          * instead. The normal behavior will be restored in dpm_complete().
>>          */
>> 
>> Because the device probe is deferred, the qcom_mhi_qrtr_probe() is not
>> called and thus MHI channels are not prepared:
>> 
>> So what this means that QRTR is not delivering messages and the QMI connection
>> is not working between ath11k and the firmware, resulting a failure in firmware
>> initialization.
>> 
>> To fix this add new function mhi_power_down_keep_dev() which doesn't destroy
>> the devices for channels during power down. This way we avoid probe defer issue
>> and finally can get ath11k hibernation working with the following patches.
>> 
>> Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30
>> 
>> Signed-off-by: Baochen Qiang <quic_bqiang at quicinc.com>
>
> Applied to mhi-next! Note that this patch is also available in mhi-immutable
> branch for ath11k maintainers to pull into their tree.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git/log/?h=mhi-immutable

Thanks, I pulled this branch to ath-next:

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=ath-next&id=231a4c893c9bb2984a8c6b7450199f59eb816ed9

This is just preparation for patches 2 and 3, those patches are not
commited yet.

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