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Message-ID: <77f6bbf6-add1-4f3b-9c10-5292e032c758@quicinc.com>
Date: Thu, 22 Feb 2024 15:48:43 +0800
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Subject: Re: [PATCH 2/3] net: qrtr: support suspend/hibernation
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To: Jeff Johnson <quic_jjohnson@quicinc.com>, <ath11k@lists.infradead.org>,
        <mhi@lists.linux.dev>
CC: <linux-wireless@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>
References: <20240221030026.10553-1-quic_bqiang@quicinc.com>
 <20240221030026.10553-3-quic_bqiang@quicinc.com>
 <dc54be43-e27f-4b5b-9b84-cf0856370abf@quicinc.com>
From: Baochen Qiang <quic_bqiang@quicinc.com>
In-Reply-To: <dc54be43-e27f-4b5b-9b84-cf0856370abf@quicinc.com>
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On 2/22/2024 2:24 AM, Jeff Johnson wrote:
> On 2/20/2024 7:00 PM, Baochen Qiang wrote:
>> MHI devices may not be destroyed during suspend/hibernation, so need
>> to unprepare/prepare MHI channels throughout the transition.
>>
>> The RFC version adds new API to MHI stack with which an MHI controller
>> driver can do unprepare/prepare directly by itself, see
>>
>> https://patchwork.kernel.org/project/linux-wireless/patch/20231127162022.518834-3-kvalo@kernel.org/
>>
>> Although it works well Mani pointed out that the design is not good
>> because MHI channels are managed by MHI client driver thus should not
>> be touched by others. See the discussion
>>
>> https://lore.kernel.org/mhi/20231127162022.518834-1-kvalo@kernel.org/
>>
>> This version changes to add suspend/resume callbacks to achieve the
>> same purpose. The suspend callback is called in the late suspend stage,
>> this means MHI channels are still alive at suspend stage, and that makes
>> it possible for an MHI controller driver to communicate with others over
>> those channels at suspend stage. While the resume callback is called in
>> the early resume stage, for a similar reason.
>>
>> 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@quicinc.com>
>> ---
>>   net/qrtr/mhi.c | 29 +++++++++++++++++++++++++++++
>>   1 file changed, 29 insertions(+)
>>
>> diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
>> index 9ced13c0627a..b54a6c2113e9 100644
>> --- a/net/qrtr/mhi.c
>> +++ b/net/qrtr/mhi.c
>> @@ -118,6 +118,32 @@ static const struct mhi_device_id qcom_mhi_qrtr_id_table[] = {
>>   };
>>   MODULE_DEVICE_TABLE(mhi, qcom_mhi_qrtr_id_table);
>>   
>> +static int qcom_mhi_qrtr_pm_suspend_late(struct device *dev)
> 
> Don't your new functions also need to be annotated as __maybe_unused?
OK, will add __maybe_unused in next version.

> 
>> +{
>> +	struct mhi_device *mhi_dev = container_of(dev, struct mhi_device, dev);
>> +
>> +	mhi_unprepare_from_transfer(mhi_dev);
>> +
>> +	return 0;
>> +}
>> +
>> +static int qcom_mhi_qrtr_pm_resume_early(struct device *dev)
>> +{
>> +	struct mhi_device *mhi_dev = container_of(dev, struct mhi_device, dev);
>> +	int rc;
>> +
>> +	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
>> +	if (rc)
>> +		dev_err(dev, "failed to prepare for autoqueue transfer %d\n", rc);
>> +
>> +	return rc;
>> +}
>> +
>> +static const struct dev_pm_ops __maybe_unused qcom_mhi_qrtr_pm_ops = {
> 
> this does not need to be __maybe_unused, see below
> 
>> +	SET_LATE_SYSTEM_SLEEP_PM_OPS(qcom_mhi_qrtr_pm_suspend_late,
>> +				     qcom_mhi_qrtr_pm_resume_early)
>> +};
>> +
>>   static struct mhi_driver qcom_mhi_qrtr_driver = {
>>   	.probe = qcom_mhi_qrtr_probe,
>>   	.remove = qcom_mhi_qrtr_remove,
>> @@ -126,6 +152,9 @@ static struct mhi_driver qcom_mhi_qrtr_driver = {
>>   	.id_table = qcom_mhi_qrtr_id_table,
>>   	.driver = {
>>   		.name = "qcom_mhi_qrtr",
>> +#ifdef CONFIG_PM
> 
> conditional compilation isn't necessary here since the 'pm' member is
> always present
Sure, will remove that in next version.

> 
>> +		.pm = &qcom_mhi_qrtr_pm_ops,
>> +#endif
>>   	},
>>   };
>>   
>