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From: Saravana Kannan <saravanak@google.com>
To: Jonathan Corbet <corbet@lwn.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Kevin Hilman <khilman@kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Len Brown <len.brown@intel.com>, Len Brown <lenb@kernel.org>,
	Pavel Machek <pavel@ucw.cz>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Marc Zyngier <maz@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Saravana Kannan <saravanak@google.com>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pm@vger.kernel.org, linux-clk@vger.kernel.org,
	devicetree@vger.kernel.org, linux-acpi@vger.kernel.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	kernel-team@android.com
Subject: [PATCH v4 1/8] driver core: fw_devlink: Detect supplier devices that will never be added
Date: Fri,  5 Feb 2021 14:26:37 -0800
Message-ID: <20210205222644.2357303-2-saravanak@google.com> (raw)
In-Reply-To: <20210205222644.2357303-1-saravanak@google.com>

During the initial parsing of firmware by fw_devlink, fw_devlink might
infer that some supplier firmware nodes would get populated as devices.
But the inference is not always correct. This patch tries to logically
detect and fix such mistakes as boot progresses or more devices probe.

fw_devlink makes a fundamental assumption that once a device binds to a
driver, it will populate (i.e: add as struct devices) all the child
firmware nodes that could be populated as devices (if they aren't
populated already).

So, whenever a device probes, we check all its child firmware nodes. If
a child firmware node has a corresponding device populated, we don't
modify the child node or its descendants. However, if a child firmware
node has not been populated as a device, we delete all the fwnode links
where the child node or its descendants are suppliers. This ensures that
no other device is blocked on a firmware node that will never be
populated as a device. We also mark such fwnodes as NOT_DEVICE, so that
no new fwnode links are created with these nodes as suppliers.

Fixes: e590474768f1 ("driver core: Set fw_devlink=on by default")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
---
 drivers/base/core.c    | 31 ++++++++++++++++++++++++++++---
 include/linux/fwnode.h |  2 ++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 484a942884ba..c95b1daabac7 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -148,6 +148,21 @@ void fwnode_links_purge(struct fwnode_handle *fwnode)
 	fwnode_links_purge_consumers(fwnode);
 }
 
+static void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode)
+{
+	struct fwnode_handle *child;
+
+	/* Don't purge consumer links of an added child */
+	if (fwnode->dev)
+		return;
+
+	fwnode->flags |= FWNODE_FLAG_NOT_DEVICE;
+	fwnode_links_purge_consumers(fwnode);
+
+	fwnode_for_each_available_child_node(fwnode, child)
+		fw_devlink_purge_absent_suppliers(child);
+}
+
 #ifdef CONFIG_SRCU
 static DEFINE_MUTEX(device_links_lock);
 DEFINE_STATIC_SRCU(device_links_srcu);
@@ -1154,12 +1169,22 @@ void device_links_driver_bound(struct device *dev)
 	LIST_HEAD(sync_list);
 
 	/*
-	 * If a device probes successfully, it's expected to have created all
+	 * If a device binds successfully, it's expected to have created all
 	 * the device links it needs to or make new device links as it needs
-	 * them. So, it no longer needs to wait on any suppliers.
+	 * them. So, fw_devlink no longer needs to create device links to any
+	 * of the device's suppliers.
+	 *
+	 * Also, if a child firmware node of this bound device is not added as
+	 * a device by now, assume it is never going to be added and make sure
+	 * other devices don't defer probe indefinitely by waiting for such a
+	 * child device.
 	 */
-	if (dev->fwnode && dev->fwnode->dev == dev)
+	if (dev->fwnode && dev->fwnode->dev == dev) {
+		struct fwnode_handle *child;
 		fwnode_links_purge_suppliers(dev->fwnode);
+		fwnode_for_each_available_child_node(dev->fwnode, child)
+			fw_devlink_purge_absent_suppliers(child);
+	}
 	device_remove_file(dev, &dev_attr_waiting_for_supplier);
 
 	device_links_write_lock();
diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index fde4ad97564c..21082f11473f 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -19,8 +19,10 @@ struct device;
  * fwnode link flags
  *
  * LINKS_ADDED: The fwnode has already be parsed to add fwnode links.
+ * NOT_DEVICE: The fwnode will never be populated as a struct device.
  */
 #define FWNODE_FLAG_LINKS_ADDED		BIT(0)
+#define FWNODE_FLAG_NOT_DEVICE		BIT(1)
 
 struct fwnode_handle {
 	struct fwnode_handle *secondary;
-- 
2.30.0.478.g8a0d178c01-goog


  reply index

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20210205222651eucas1p28ef87073dea33c1c5224c14aa203bec5@eucas1p2.samsung.com>
2021-02-05 22:26 ` [PATCH v4 0/8] Make fw_devlink=on more forgiving Saravana Kannan
2021-02-05 22:26   ` Saravana Kannan [this message]
2021-02-05 22:26   ` [PATCH v4 2/8] of: property: Don't add links to absent suppliers Saravana Kannan
2021-02-09 21:25     ` Rob Herring
2021-02-05 22:26   ` [PATCH v4 3/8] driver core: Add fw_devlink.strict kernel param Saravana Kannan
2021-02-05 22:26   ` [PATCH v4 4/8] of: property: Add fw_devlink support for optional properties Saravana Kannan
2021-02-09 21:33     ` Rob Herring
2021-02-09 21:54       ` Saravana Kannan
2021-02-10  8:25         ` Geert Uytterhoeven
2021-02-05 22:26   ` [PATCH v4 5/8] driver core: fw_devlink: Handle suppliers that don't use driver core Saravana Kannan
2021-02-05 22:26   ` [PATCH v4 6/8] irqdomain: Mark fwnodes when their irqdomain is added/removed Saravana Kannan
2021-02-05 22:26   ` [PATCH v4 7/8] PM: domains: Mark fwnodes when their powerdomain " Saravana Kannan
2021-02-05 22:26   ` [PATCH v4 8/8] clk: Mark fwnodes when their clock provider " Saravana Kannan
2021-02-08 15:38     ` Rob Herring
2021-02-08 23:34       ` Saravana Kannan
2021-02-10 11:44     ` [PATCH] clk: Mark fwnodes when their clock provider is added Tudor Ambarus
2021-02-10 11:44       ` Tudor Ambarus
2021-02-11 13:00         ` Greg KH
2021-02-13  0:37           ` Stephen Boyd
     [not found]         ` <CGME20210325133159eucas1p297b769beb681743fb32d362a86cc6e3e@eucas1p2.samsung.com>
2021-03-25 13:31           ` Marek Szyprowski
2021-03-25 15:47             ` Geert Uytterhoeven
2021-03-25 18:25             ` Nicolas Saenz Julienne
2021-03-26 18:13               ` Stephen Boyd
2021-03-26 18:29                 ` Geert Uytterhoeven
     [not found]                   ` <161705310317.3012082.15148238105608149214@swboyd.mtv.corp.google.com>
2021-03-29 23:28                     ` Saravana Kannan
     [not found]                       ` <161706920822.3012082.10047587064612237296@swboyd.mtv.corp.google.com>
2021-03-30  6:58                         ` Geert Uytterhoeven
     [not found]                           ` <161715734080.2260335.881350237641202575@swboyd.mtv.corp.google.com>
2021-03-31  7:05                             ` Geert Uytterhoeven
     [not found]                               ` <161721871083.2260335.2392646934517115770@swboyd.mtv.corp.google.com>
2021-04-05 11:04                                 ` Nicolas Saenz Julienne
2021-04-21  3:26         ` Guenter Roeck
2021-04-21  7:00           ` Saravana Kannan
2021-02-10 19:13       ` Saravana Kannan
2021-03-30 15:42       ` Guenter Roeck
2021-03-30 16:26         ` Saravana Kannan
     [not found]     ` <161317679292.1254594.15797939257637374295@swboyd.mtv.corp.google.com>
2021-02-14 21:15       ` [PATCH v4 8/8] clk: Mark fwnodes when their clock provider is added/removed Saravana Kannan
2021-02-06  2:45   ` [PATCH v4 0/8] Make fw_devlink=on more forgiving Saravana Kannan
2021-02-06 19:41   ` Geert Uytterhoeven
2021-02-06 20:47     ` Saravana Kannan
2021-02-08  8:40   ` Marek Szyprowski
2021-02-08 23:57     ` Saravana Kannan
2021-02-10  8:19   ` Tudor.Ambarus
2021-02-10  8:54     ` Saravana Kannan
2021-02-10 10:02       ` Tudor.Ambarus
2021-02-10 19:14         ` Saravana Kannan
2021-02-11 13:00   ` Geert Uytterhoeven
2021-02-11 13:05     ` Geert Uytterhoeven
2021-02-12  2:59     ` Saravana Kannan
2021-02-12  8:14       ` Geert Uytterhoeven
2021-02-12 20:57         ` Saravana Kannan
2021-02-15 12:38       ` Geert Uytterhoeven
2021-02-15 21:26         ` Saravana Kannan
2021-02-16  8:05           ` Geert Uytterhoeven
2021-02-16 18:48             ` Saravana Kannan
2021-02-16 20:31               ` Geert Uytterhoeven
2021-02-17 23:57                 ` Saravana Kannan
2021-02-25  9:21                   ` Geert Uytterhoeven
2021-02-15 15:16       ` Geert Uytterhoeven
2021-02-15 21:57         ` Saravana Kannan
2021-02-16 12:58           ` Geert Uytterhoeven
2021-02-15 11:19     ` Geert Uytterhoeven

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