linux-kernel - [PATCH 2/3] rtc: max77686: Make wakeup support configurable

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Message-Id: <20200417170825.2551367-2-thierry.reding@gmail.com>
Date:   Fri, 17 Apr 2020 19:08:24 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Jon Hunter <jonathanh@...dia.com>, devicetree@...r.kernel.org,
        linux-rtc@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] rtc: max77686: Make wakeup support configurable

From: Thierry Reding <treding@...dia.com>

Use the standard "wakeup-source" device tree property to determine if
the RTC can act as a wakeup source for the system. Note that the driver
by default always assumes that the RTC can act as a wakeup source, but
whether it can really do so or not always depends on how it is hooked
up.

In order to preserve backwards compatibility with older device trees,
only parse the "wakeup-source" property when a device tree node was
associated with the RTC device. This doesn't typically happen because
the top-level MFD driver doesn't list any compatible strings that can
be used to map child nodes to child devices. As a fallback, check if a
child node named "rtc" exists and use that instead.

Signed-off-by: Thierry Reding <treding@...dia.com>
---
Note that we could obviously add support to the MFD driver to match
subdevices to their device tree nodes by compatible string, but there
are side-effects, such as the driver core complaining about the lack
of a DMA mask for these devices. That in turn could also be fixed but
it ends up all being rather hacky, so just looking up a child node by
name seems like a good compromise, especially since there are already
such subnodes for some of the other subdevices of this PMIC.
---
 drivers/rtc/rtc-max77686.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-max77686.c b/drivers/rtc/rtc-max77686.c
index d5a0e27dd0a0..35fd74b83626 100644
--- a/drivers/rtc/rtc-max77686.c
+++ b/drivers/rtc/rtc-max77686.c
@@ -722,6 +722,8 @@ static int max77686_rtc_probe(struct platform_device *pdev)
 {
 	struct max77686_rtc_info *info;
 	const struct platform_device_id *id = platform_get_device_id(pdev);
+	struct device_node *np = of_node_get(pdev->dev.of_node);
+	bool wakeup = true;
 	int ret;
 
 	info = devm_kzalloc(&pdev->dev, sizeof(struct max77686_rtc_info),
@@ -746,7 +748,21 @@ static int max77686_rtc_probe(struct platform_device *pdev)
 		goto err_rtc;
 	}
 
-	device_init_wakeup(&pdev->dev, 1);
+	/*
+	 * Only check for the wakeup-source property if there's an actual
+	 * device tree node for the RTC. If no device tree node had been
+	 * attached during device instantiation, try looking up the "rtc"
+	 * child node of the parent's device tree node.
+	 */
+	if (!np && pdev->dev.parent->of_node)
+		np = of_get_child_by_name(pdev->dev.parent->of_node, "rtc");
+
+	if (np) {
+		wakeup = of_property_read_bool(np, "wakeup-source");
+		of_node_put(np);
+	}
+
+	device_init_wakeup(&pdev->dev, wakeup);
 
 	info->rtc_dev = devm_rtc_device_register(&pdev->dev, id->name,
 					&max77686_rtc_ops, THIS_MODULE);
-- 
2.24.1