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

[Anson Huang]

> Subject: RE: [PATCH] mailbox: imx: Add context save/restore for
> suspend/resume
> 
> > From: Anson Huang <Anson.Huang@xxxxxxx>
> > 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@xxxxxxx>
> 
> 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.

This is NOT corner case, it can be reproduced with our imx_5.4.y very
easily, and this issue cause me many days to debug...Also cause Clark's
effort to help test it a lot for many days...

I do NOT think it makes sense to first send out your patch with bug for review,
And then add another patch to fix it. 1 patch is enough for this feature.