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From: Kalle Valo <kvalo@kernel.org>
To: Baochen Qiang <quic_bqiang@quicinc.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,  "Kalle Valo
 (QUIC)" <quic_kvalo@quicinc.com>,  <ath11k@lists.infradead.org>,
  <linux-wireless@vger.kernel.org>,  <linux-arm-msm@vger.kernel.org>,
  <mhi@lists.linux.dev>,  <davem@davemloft.net>,  <edumazet@google.com>,
  <kuba@kernel.org>,  <pabeni@redhat.com>,  <netdev@vger.kernel.org>
Subject: Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()
References: <20240228022243.17762-1-quic_bqiang@quicinc.com>
	<20240228022243.17762-2-quic_bqiang@quicinc.com>
	<20240229101202.GB2999@thinkpad>
	<531daaa9-cf14-4812-8908-c617bd25bc08@quicinc.com>
Date: Thu, 29 Feb 2024 21:35:34 +0200
In-Reply-To: <531daaa9-cf14-4812-8908-c617bd25bc08@quicinc.com> (Baochen
	Qiang's message of "Thu, 29 Feb 2024 18:33:43 +0800")
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Baochen Qiang <quic_bqiang@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@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.

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