linux-kernel - RE: [PATCH] mailbox: imx: Add context save/restore for suspend/resume

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Date:   Fri, 24 Apr 2020 02:27:05 +0000
From:   Aisheng Dong <aisheng.dong@....com>
To:     Anson Huang <anson.huang@....com>,
        "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] mailbox: imx: Add context save/restore for suspend/resume

> From: Anson Huang <Anson.Huang@....com>
> Sent: Friday, April 24, 2020 7:01 AM
> 
> For "mem" mode suspend on i.MX8 SoCs, MU settings could be lost because its
> power is off, so save/restore is needed for MU settings during suspend/resume.
> However, the restore can ONLY be done when MU settings are actually lost, for
> the scenario of settings NOT lost in "freeze" mode suspend, since there could be
> still IPC going on multiple CPUs, restoring the MU settings could overwrite the
> TIE by mistake and cause system freeze, so need to make sure ONLY restore the
> MU settings when it is powered off.
> 
> Signed-off-by: Anson Huang <Anson.Huang@....com>

As mentioned before, we'd better keep the original author.

> ---
>  drivers/mailbox/imx-mailbox.c | 35
> +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/drivers/mailbox/imx-mailbox.c b/drivers/mailbox/imx-mailbox.c
> index 97bf0ac..b53cf63 100644
> --- a/drivers/mailbox/imx-mailbox.c
> +++ b/drivers/mailbox/imx-mailbox.c
> @@ -67,6 +67,8 @@ struct imx_mu_priv {
>  	struct clk		*clk;
>  	int			irq;
> 
> +	u32 xcr;
> +
>  	bool			side_b;
>  };
> 
> @@ -583,12 +585,45 @@ static const struct of_device_id imx_mu_dt_ids[] =
> {  };  MODULE_DEVICE_TABLE(of, imx_mu_dt_ids);
> 
> +static int imx_mu_suspend_noirq(struct device *dev) {
> +	struct imx_mu_priv *priv = dev_get_drvdata(dev);
> +
> +	priv->xcr = imx_mu_read(priv, priv->dcfg->xCR);
> +
> +	return 0;
> +}
> +
> +static int imx_mu_resume_noirq(struct device *dev) {
> +	struct imx_mu_priv *priv = dev_get_drvdata(dev);
> +
> +	/*
> +	 * ONLY restore MU when context lost, the TIE could
> +	 * be set during noirq resume as there is MU data
> +	 * communication going on, and restore the saved
> +	 * value will overwrite the TIE and cause MU data
> +	 * send failed, may lead to system freeze. This issue
> +	 * is observed by testing freeze mode suspend.
> +	 */
> +	if (!imx_mu_read(priv, priv->dcfg->xCR))
> +		imx_mu_write(priv, priv->xcr, priv->dcfg->xCR);

This could be separate patch if it aims to fix a specific corner case.

Regards
Aisheng

> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops imx_mu_pm_ops = {
> +	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(imx_mu_suspend_noirq,
> +				      imx_mu_resume_noirq)
> +};
> +
>  static struct platform_driver imx_mu_driver = {
>  	.probe		= imx_mu_probe,
>  	.remove		= imx_mu_remove,
>  	.driver = {
>  		.name	= "imx_mu",
>  		.of_match_table = imx_mu_dt_ids,
> +		.pm = &imx_mu_pm_ops,
>  	},
>  };
>  module_platform_driver(imx_mu_driver);
> --
> 2.7.4