[PATCH] PCI/pwrctl: pwrseq: abandon probe on pre-pwrseq device-trees

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Old device trees for some platforms already define wifi nodes for the WCN
family of chips since before power sequencing was added upstream.

These nodes don't consume the regulator outputs from the PMU and if we
allow this driver to bind to one of such "incomplete" nodes, we'll see
a kernel log error about the indefinite probe deferral.

Let's check the existence of the regulator supply that exists on all WCN
models before moving forward.

Fixes: 6140d185a43d ("PCI/pwrctl: Add a PCI power control driver for power sequenced devices")
Reported-by: Johan Hovold <johan@kernel.org>
Closes: https://lore.kernel.org/all/Zv565olMDDGHyYVt@hovoldconsulting.com/
Suggested-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/pci/pwrctl/pci-pwrctl-pwrseq.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c b/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
index a23a4312574b..8ed613655d4a 100644
--- a/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
+++ b/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
@@ -9,6 +9,7 @@
 #include <linux/of.h>
 #include <linux/pci-pwrctl.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
 #include <linux/pwrseq/consumer.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -31,6 +32,25 @@ static int pci_pwrctl_pwrseq_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	int ret;
 
+	/*
+	 * Old device trees for some platforms already define wifi nodes for
+	 * the WCN family of chips since before power sequencing was added
+	 * upstream.
+	 *
+	 * These nodes don't consume the regulator outputs from the PMU and
+	 * if we allow this driver to bind to one of such "incomplete" nodes,
+	 * we'll see a kernel log error about the indefinite probe deferral.
+	 *
+	 * Let's check the existence of the regulator supply that exists on all
+	 * WCN models before moving forward.
+	 *
+	 * NOTE: If this driver is ever used to support a device other than
+	 * a WCN chip, the following lines should become conditional and depend
+	 * on the compatible string.
+	 */
+	if (!device_property_present(dev, "vddaon-supply"))
+		return -ENODEV;
+
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
-- 
2.43.0