Re: [PATCH v3 2/6] firmware: ti_sci: Partial-IO support

[Markus Schneider-Pargmann]

Hi Nishanth,

On Fri, Oct 25, 2024 at 12:42:04PM GMT, Nishanth Menon wrote:
> On 16:39-20241012, Markus Schneider-Pargmann wrote:
> [...]
> > 
> > The possible wakeup devices are found by checking which devices are
> > powered by the regulator supplying the "vddshv_canuart" line. These are
> > considered possible wakeup sources. Only wakeup sources that are
> > actually enabled by the user will be considered as a an active wakeup
> > source. If none of the wakeup sources are enabled the system will do a
> > normal poweroff. If at least one wakeup source is enabled it will
> > instead send a TI_SCI_MSG_PREPARE_SLEEP message from the sys_off
> > handler. Sending this message will result in an immediate shutdown of
> > the system. No execution is expected after this point. The code will
> > wait for 5s and do an emergency_restart afterwards if Partial-IO wasn't
> > entered at that point.
> > 
> [...]
> 
> > +static bool tisci_canuart_wakeup_enabled(struct ti_sci_info *info)
> > +{
> > +	static const char canuart_name[] = "vddshv_canuart";
> > +	struct device_node *wakeup_node = NULL;
> > +
> > +	for (wakeup_node = of_find_node_with_property(NULL, "vio-supply");
> > +	     wakeup_node;
> > +	     wakeup_node = of_find_node_with_property(wakeup_node, "vio-supply")) {
> > +		struct device_node *supply_node;
> > +		const char *supply_name;
> > +		struct platform_device *pdev;
> > +		int ret;
> > +
> > +		supply_node = of_parse_phandle(wakeup_node, "vio-supply", 0);
> > +		if (!supply_node)
> > +			continue;
> > +
> > +		ret = of_property_read_string(supply_node, "regulator-name", &supply_name);
> > +		of_node_put(supply_node);
> > +		if (ret) {
> > +			dev_warn(info->dev, "Failed to parse vio-supply phandle at %pOF %d\n",
> > +				 wakeup_node, ret);
> > +			continue;
> > +		}
> > +
> > +		if (strncmp(canuart_name, supply_name, strlen(canuart_name)))
> > +			continue;
> > +
> > +		pdev = of_find_device_by_node(wakeup_node);
> > +		if (!pdev)
> > +			continue;
> > +
> > +		if (device_may_wakeup(&pdev->dev)) {
> > +			dev_dbg(info->dev, "%pOF identified as wakeup source for Partial-IO\n",
> > +				wakeup_node);
> > +			put_device(&pdev->dev);
> > +			of_node_put(wakeup_node);
> > +			return true;
> > +		}
> > +		put_device(&pdev->dev);
> > +	}
> > +
> > +	return false;
> > +}
> > +
> 
> What is the binding that supports this? I just do not think that
> scanning the entire tree for vio-supply implies you will get thr right
> property here.
> 
> Just giving an example to illustrate this point:
> Documentation/devicetree/bindings/net/wireless/ti,wl1251.txt says it
> needs vio-supply -> so i have a node with the wireless supply as
> vio-supply -> Since we are scanning from NULL for vio-supply, we hit
> that, that is a bad choice for enabling io-retention.

There is no bining that specifically supports this as I think it is not
needed. The devices that are capable to wakeup the system from
Partial-IO are all powered through one supply line that is always-on. It
is called 'vddshv_canuart' and the name of this supply is checked
in the above code as well. Yes I am using 'vio-supply', but only to
search for the potential consumers of this supply.
So wl1251 will be skipped in above code at

  if (strncmp(canuart_name, supply_name, strlen(canuart_name)))

Best
Markus

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