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Date: Tue, 27 Feb 2024 17:46:02 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Baochen Qiang <quic_bqiang@quicinc.com>
Cc: ath11k@lists.infradead.org, linux-wireless@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, mhi@lists.linux.dev
Subject: Re: [PATCH v3 2/3] net: qrtr: support suspend/hibernation
Message-ID: <20240227121602.GM2587@thinkpad>
References: <20240227104427.7505-1-quic_bqiang@quicinc.com>
 <20240227104427.7505-3-quic_bqiang@quicinc.com>
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In-Reply-To: <20240227104427.7505-3-quic_bqiang@quicinc.com>

On Tue, Feb 27, 2024 at 06:44:26PM +0800, Baochen Qiang wrote:
> MHI devices may not be destroyed during suspend/hibernation, so need
> to unprepare/prepare MHI channels throughout the transition, this is
> done by adding suspend/resume callbacks.
> 
> 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.
> 
> Also note that we won't do unprepare/prepare when MHI device is in
> suspend state because it's pointless if MHI is only meant to go through
> a suspend/resume transition, instead of a complete power cycle.
> 
> 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>

Btw, you forgot to CC netdev folks. Here is the list that get_maintainer.pl
returns:

"David S. Miller" <davem@davemloft.net> (maintainer:NETWORKING [GENERAL])
Eric Dumazet <edumazet@google.com> (maintainer:NETWORKING [GENERAL])
Jakub Kicinski <kuba@kernel.org> (maintainer:NETWORKING [GENERAL])
Paolo Abeni <pabeni@redhat.com> (maintainer:NETWORKING [GENERAL])
netdev@vger.kernel.org (open list:NETWORKING [GENERAL])

- Mani

> ---
>  net/qrtr/mhi.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
> index 9ced13c0627a..69f53625a049 100644
> --- a/net/qrtr/mhi.c
> +++ b/net/qrtr/mhi.c
> @@ -118,6 +118,51 @@ static const struct mhi_device_id qcom_mhi_qrtr_id_table[] = {
>  };
>  MODULE_DEVICE_TABLE(mhi, qcom_mhi_qrtr_id_table);
>  
> +static int __maybe_unused qcom_mhi_qrtr_pm_suspend_late(struct device *dev)
> +{
> +	struct mhi_device *mhi_dev = container_of(dev, struct mhi_device, dev);
> +	enum mhi_state state;
> +
> +	state = mhi_get_mhi_state(mhi_dev->mhi_cntrl);
> +	/*
> +	 * If the device is in suspend state, then no need for the
> +	 * client driver to unprepare the channels.
> +	 */
> +	if (state == MHI_STATE_M3)
> +		return 0;
> +
> +	mhi_unprepare_from_transfer(mhi_dev);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused qcom_mhi_qrtr_pm_resume_early(struct device *dev)
> +{
> +	struct mhi_device *mhi_dev = container_of(dev, struct mhi_device, dev);
> +	enum mhi_state state;
> +	int rc;
> +
> +	state = mhi_get_mhi_state(mhi_dev->mhi_cntrl);
> +	/*
> +	 * If the device is in suspend state, we won't unprepare channels
> +	 * in suspend callback, therefore no need to prepare channels when
> +	 * resume.
> +	 */
> +	if (state == MHI_STATE_M3)
> +		return 0;
> +
> +	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 qcom_mhi_qrtr_pm_ops = {
> +	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 +171,7 @@ static struct mhi_driver qcom_mhi_qrtr_driver = {
>  	.id_table = qcom_mhi_qrtr_id_table,
>  	.driver = {
>  		.name = "qcom_mhi_qrtr",
> +		.pm = &qcom_mhi_qrtr_pm_ops,
>  	},
>  };
>  
> -- 
> 2.25.1
> 

-- 
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