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Date:   Thu, 29 Aug 2019 00:46:00 -0700
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Message-Id: <20190829074603.70424-5-saravanak@google.com>
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Subject: [PATCH v10 4/7] of/platform: Pause/resume sync state during init and of_platform_populate()
From:   Saravana Kannan <saravanak@google.com>
To:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>, Len Brown <lenb@kernel.org>
Cc:     Saravana Kannan <saravanak@google.com>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-acpi@vger.kernel.org, clang-built-linux@googlegroups.com,
        David Collins <collinsd@codeaurora.org>,
        kernel-team@android.com
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When all the top level devices are populated from DT during kernel
init, the supplier devices could be added and probed before the
consumer devices are added and linked to the suppliers. To avoid the
sync_state() callback from being called prematurely, pause the
sync_state() callbacks before populating the devices and resume them
at late_initcall_sync().

Similarly, when children devices are populated from a module using
of_platform_populate(), there could be supplier-consumer dependencies
between the children devices that are populated. To avoid the same
problem with sync_state() being called prematurely, pause and resume
sync_state() callbacks across of_platform_populate().

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 drivers/of/platform.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index b47a2292fe8e..d93891a05f60 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -480,6 +480,7 @@ int of_platform_populate(struct device_node *root,
 	pr_debug("%s()\n", __func__);
 	pr_debug(" starting at: %pOF\n", root);
 
+	device_links_supplier_sync_state_pause();
 	for_each_child_of_node(root, child) {
 		rc = of_platform_bus_create(child, matches, lookup, parent, true);
 		if (rc) {
@@ -487,6 +488,8 @@ int of_platform_populate(struct device_node *root,
 			break;
 		}
 	}
+	device_links_supplier_sync_state_resume();
+
 	of_node_set_flag(root, OF_POPULATED_BUS);
 
 	of_node_put(root);
@@ -518,6 +521,7 @@ static int __init of_platform_default_populate_init(void)
 	if (!of_have_populated_dt())
 		return -ENODEV;
 
+	device_links_supplier_sync_state_pause();
 	/*
 	 * Handle certain compatibles explicitly, since we don't want to create
 	 * platform_devices for every node in /reserved-memory with a
@@ -538,6 +542,14 @@ static int __init of_platform_default_populate_init(void)
 	return 0;
 }
 arch_initcall_sync(of_platform_default_populate_init);
+
+static int __init of_platform_sync_state_init(void)
+{
+	if (of_have_populated_dt())
+		device_links_supplier_sync_state_resume();
+	return 0;
+}
+late_initcall_sync(of_platform_sync_state_init);
 #endif
 
 int of_platform_device_destroy(struct device *dev, void *data)
-- 
2.23.0.187.g17f5b7556c-goog