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Message-ID: <dc54be43-e27f-4b5b-9b84-cf0856370abf@quicinc.com>
Date: Wed, 21 Feb 2024 10:24:44 -0800
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Subject: Re: [PATCH 2/3] net: qrtr: support suspend/hibernation
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To: Baochen Qiang <quic_bqiang@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>
From: Jeff Johnson <quic_jjohnson@quicinc.com>
In-Reply-To: <20240221030026.10553-3-quic_bqiang@quicinc.com>
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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?

> +{
> +	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

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