[PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

[Baochen Qiang]

On 3/1/2024 3:35 AM, Kalle Valo wrote:
> Baochen Qiang <quic_bqiang at quicinc.com> writes:
> 
>> On 2/29/2024 6:12 PM, Manivannan Sadhasivam wrote:
>>> On Wed, Feb 28, 2024 at 10:22:41AM +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: Kalle Valo <quic_kvalo at quicinc.com>
>>>
>>> Did Kalle co-author this patch? If so, his Co-developed-by tag should
>>> be added.
>>
>> Hmm, I'm not sure...  I would like Kalle's thoughts on this.
> 
> IIRC I did only some simple cleanup before submitting the patch so I
> don't think Co-developed-by is justified. I'm also fine with removing my
> Signed-off-by.
Thanks Kalle.

Hi Mani, so according to Kalle's comments, I'd like to keep the patch as is.

>