Re: [PATCH v2 2/2] remoteproc: imx_rproc: handle system off for i.MX7ULP

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Tue, Jul 30, 2024 at 08:06:22AM +0000, Peng Fan wrote:
> > Subject: Re: [PATCH v2 2/2] remoteproc: imx_rproc: handle system off
> > for i.MX7ULP
> > 
> > On Fri, Jul 19, 2024 at 04:49:04PM +0800, Peng Fan (OSS) wrote:
> > > From: Peng Fan <peng.fan@nxp.com>
> > >
> > > The i.MX7ULP Cortex-A7 is under control of Cortex-M4. The
> > i.MX7ULP
> > > Linux poweroff and restart rely on rpmsg driver to send a message to
> > > Cortex-M4 firmware. Then Cortex-A7 could poweroff or restart by
> > > Cortex-M4 to configure the i.MX7ULP power controller properly.
> > >
> > > However the reboot and restart kernel common code use atomic
> > notifier,
> > > so with blocking tx mailbox will trigger kernel dump, because of
> > > blocking mailbox will use wait_for_completion_timeout. In such case,
> > > linux no need to wait for completion.
> > >
> > > Current patch is to use non-blocking tx mailbox channel when system
> > is
> > > going to poweroff or restart.
> > >
> > > Signed-off-by: Peng Fan <peng.fan@nxp.com>
> > > ---
> > >  drivers/remoteproc/imx_rproc.c | 36
> > > ++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 36 insertions(+)
> > >
> > > diff --git a/drivers/remoteproc/imx_rproc.c
> > > b/drivers/remoteproc/imx_rproc.c index
> > 01cf1dfb2e87..e1abf110abc9
> > > 100644
> > > --- a/drivers/remoteproc/imx_rproc.c
> > > +++ b/drivers/remoteproc/imx_rproc.c
> > > @@ -18,6 +18,7 @@
> > >  #include <linux/of_reserved_mem.h>
> > >  #include <linux/platform_device.h>
> > >  #include <linux/pm_domain.h>
> > > +#include <linux/reboot.h>
> > >  #include <linux/regmap.h>
> > >  #include <linux/remoteproc.h>
> > >  #include <linux/workqueue.h>
> > > @@ -114,6 +115,7 @@ struct imx_rproc {
> > >  	u32				entry;		/* cpu start
> > address */
> > >  	u32				core_index;
> > >  	struct dev_pm_domain_list	*pd_list;
> > > +	struct sys_off_data		data;
> > 
> > What is this for?  I don't see it used in this patch.
> 
> Oh, it was added when I was developing this feature, but in the end
> this seems not needed.
> 
> > 
> > >  };
> > >
> > >  static const struct imx_rproc_att imx_rproc_att_imx93[] = { @@
> > > -1050,6 +1052,22 @@ static int imx_rproc_clk_enable(struct
> > imx_rproc *priv)
> > >  	return 0;
> > >  }
> > >
> > > +static int imx_rproc_sys_off_handler(struct sys_off_data *data) {
> > > +	struct rproc *rproc = data->cb_data;
> > > +	int ret;
> > > +
> > > +	imx_rproc_free_mbox(rproc);
> > > +
> > > +	ret = imx_rproc_xtr_mbox_init(rproc, false);
> > > +	if (ret) {
> > > +		dev_err(&rproc->dev, "Failed to request non-blocking
> > mbox\n");
> > > +		return NOTIFY_BAD;
> > > +	}
> > > +
> > > +	return NOTIFY_DONE;
> > > +}
> > > +
> > >  static int imx_rproc_probe(struct platform_device *pdev)  {
> > >  	struct device *dev = &pdev->dev;
> > > @@ -1104,6 +1122,24 @@ static int imx_rproc_probe(struct
> > platform_device *pdev)
> > >  	if (rproc->state != RPROC_DETACHED)
> > >  		rproc->auto_boot = of_property_read_bool(np,
> > "fsl,auto-boot");
> > >
> > > +	if (of_device_is_compatible(dev->of_node, "fsl,imx7ulp-cm4"))
> > {
> > > +		ret = devm_register_sys_off_handler(dev,
> > SYS_OFF_MODE_POWER_OFF_PREPARE,
> > > +
> > SYS_OFF_PRIO_DEFAULT,
> > > +
> > imx_rproc_sys_off_handler, rproc);
> > 
> > Why does the mailbox needs to be set up again when the system is
> > going down...
> 
> As wrote in commit message:
> "i.MX7ULP Linux poweroff and restart rely on rpmsg driver to send a
> message," so need to set up mailbox in non-blocking way to send
> a message to M4 side.
> 
> > 
> > > +		if (ret) {
> > > +			dev_err(dev, "register power off handler
> > failure\n");
> > > +			goto err_put_clk;
> > > +		}
> > > +
> > > +		ret = devm_register_sys_off_handler(dev,
> > SYS_OFF_MODE_RESTART_PREPARE,
> > > +
> > SYS_OFF_PRIO_DEFAULT,
> > > +
> > imx_rproc_sys_off_handler, rproc);
> > 
> > ... and why does it need to be free'd when the system is going up?
> 
> 
> Sorry, I not get your point. The free is in imx_rproc_sys_off_handler.
> During system booting, the mailbox is not freed.

Why is the same operation done at both startup and shutdown - that is not clear.

I am currently away from the office, returning on August 12th.  As such I will
not be following up on this thread until then.

> 
> Thanks,
> Peng.
> 
> > 
> > > +		if (ret) {
> > > +			dev_err(dev, "register restart handler
> > failure\n");
> > > +			goto err_put_clk;
> > > +		}
> > > +	}
> > > +
> > >  	ret = rproc_add(rproc);
> > >  	if (ret) {
> > >  		dev_err(dev, "rproc_add failed\n");
> > >
> > > --
> > > 2.37.1
> > >
> > >