netdev - Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep

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Message-ID: <1d0f2a64-85d1-4f2d-81f1-6a6938ad3d34@quicinc.com>
Date: Wed, 28 Feb 2024 07:09:56 -0800
From: Jeff Johnson <quic_jjohnson@...cinc.com>
To: Baochen Qiang <quic_bqiang@...cinc.com>, <ath11k@...ts.infradead.org>,
        <manivannan.sadhasivam@...aro.org>
CC: <linux-wireless@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <mhi@...ts.linux.dev>, <davem@...emloft.net>, <edumazet@...gle.com>,
        <kuba@...nel.org>, <pabeni@...hat.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

On 2/27/2024 6:22 PM, 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@...cinc.com>
> Signed-off-by: Baochen Qiang <quic_bqiang@...cinc.com>
Reviewed-by: Jeff Johnson <quic_jjohnson@...cinc.com>