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authorLinus Torvalds <torvalds@linux-foundation.org>2019-11-27 11:06:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-11-27 11:06:20 -0800
commit9a3d7fd275be4559277667228902824165153c80 (patch)
tree09e74ef51c6388ac42b6123ad789ebc5b6ad8ed6 /Documentation/driver-api
parent0dd09bc02c1bad55e92306ca83b38b3cf48b9f40 (diff)
parent0e4a459f56c32d3e52ae69a4b447db2f48a65f44 (diff)
downloadlinux-9a3d7fd275be4559277667228902824165153c80.tar.bz2
Merge tag 'driver-core-5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core updates from Greg KH: "Here is the "big" set of driver core patches for 5.5-rc1 There's a few minor cleanups and fixes in here, but the majority of the patches in here fall into two buckets: - debugfs api cleanups and fixes - driver core device link support for boot dependancy issues The debugfs api cleanups are working to slowly refactor the debugfs apis so that it is even harder to use incorrectly. That work has been happening for the past few kernel releases and will continue over time, it's a long-term project/goal The driver core device link support missed 5.4 by just a bit, so it's been sitting and baking for many months now. It's from Saravana Kannan to help resolve the problems that DT-based systems have at boot time with dependancy graphs and kernel modules. Turns out that no one has actually tried to build a generic arm64 kernel with loads of modules and have it "just work" for a variety of platforms (like a distro kernel). The big problem turned out to be a lack of dependency information between different areas of DT entries, and the work here resolves that problem and now allows devices to boot properly, and quicker than a monolith kernel. All of these patches have been in linux-next for a long time with no reported issues" * tag 'driver-core-5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (68 commits) tracing: Remove unnecessary DEBUG_FS dependency of: property: Add device link support for interrupt-parent, dmas and -gpio(s) debugfs: Fix !DEBUG_FS debugfs_create_automount of: property: Add device link support for "iommu-map" of: property: Fix the semantics of of_is_ancestor_of() i2c: of: Populate fwnode in of_i2c_get_board_info() drivers: base: Fix Kconfig indentation firmware_loader: Fix labels with comma for builtin firmware driver core: Allow device link operations inside sync_state() driver core: platform: Declare ret variable only once cpu-topology: declare parse_acpi_topology in <linux/arch_topology.h> crypto: hisilicon: no need to check return value of debugfs_create functions driver core: platform: use the correct callback type for bus_find_device firmware_class: make firmware caching configurable driver core: Clarify documentation for fwnode_operations.add_links() mailbox: tegra: Fix superfluous IRQ error message net: caif: Fix debugfs on 64-bit platforms mac80211: Use debugfs_create_xul() helper media: c8sectpfe: no need to check return value of debugfs_create functions of: property: Add device link support for iommus, mboxes and io-channels ...
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r--Documentation/driver-api/device_link.rst3
-rw-r--r--Documentation/driver-api/driver-model/devres.rst4
-rw-r--r--Documentation/driver-api/driver-model/driver.rst43
3 files changed, 49 insertions, 1 deletions
diff --git a/Documentation/driver-api/device_link.rst b/Documentation/driver-api/device_link.rst
index 1b5020ec6517..bc2d89af88ce 100644
--- a/Documentation/driver-api/device_link.rst
+++ b/Documentation/driver-api/device_link.rst
@@ -281,7 +281,8 @@ State machine
:c:func:`driver_bound()`.)
* Before a consumer device is probed, presence of supplier drivers is
- verified by checking that links to suppliers are in ``DL_STATE_AVAILABLE``
+ verified by checking the consumer device is not in the wait_for_suppliers
+ list and by checking that links to suppliers are in ``DL_STATE_AVAILABLE``
state. The state of the links is updated to ``DL_STATE_CONSUMER_PROBE``.
(Call to :c:func:`device_links_check_suppliers()` from
:c:func:`really_probe()`.)
diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index a100bef54952..4ab193319d8c 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -316,6 +316,10 @@ IOMAP
devm_ioremap_nocache()
devm_ioremap_wc()
devm_ioremap_resource() : checks resource, requests memory region, ioremaps
+ devm_ioremap_resource_wc()
+ devm_platform_ioremap_resource() : calls devm_ioremap_resource() for platform device
+ devm_platform_ioremap_resource_wc()
+ devm_platform_ioremap_resource_byname()
devm_iounmap()
pcim_iomap()
pcim_iomap_regions() : do request_region() and iomap() on multiple BARs
diff --git a/Documentation/driver-api/driver-model/driver.rst b/Documentation/driver-api/driver-model/driver.rst
index 11d281506a04..baa6a85c8287 100644
--- a/Documentation/driver-api/driver-model/driver.rst
+++ b/Documentation/driver-api/driver-model/driver.rst
@@ -169,6 +169,49 @@ A driver's probe() may return a negative errno value to indicate that
the driver did not bind to this device, in which case it should have
released all resources it allocated::
+ void (*sync_state)(struct device *dev);
+
+sync_state is called only once for a device. It's called when all the consumer
+devices of the device have successfully probed. The list of consumers of the
+device is obtained by looking at the device links connecting that device to its
+consumer devices.
+
+The first attempt to call sync_state() is made during late_initcall_sync() to
+give firmware and drivers time to link devices to each other. During the first
+attempt at calling sync_state(), if all the consumers of the device at that
+point in time have already probed successfully, sync_state() is called right
+away. If there are no consumers of the device during the first attempt, that
+too is considered as "all consumers of the device have probed" and sync_state()
+is called right away.
+
+If during the first attempt at calling sync_state() for a device, there are
+still consumers that haven't probed successfully, the sync_state() call is
+postponed and reattempted in the future only when one or more consumers of the
+device probe successfully. If during the reattempt, the driver core finds that
+there are one or more consumers of the device that haven't probed yet, then
+sync_state() call is postponed again.
+
+A typical use case for sync_state() is to have the kernel cleanly take over
+management of devices from the bootloader. For example, if a device is left on
+and at a particular hardware configuration by the bootloader, the device's
+driver might need to keep the device in the boot configuration until all the
+consumers of the device have probed. Once all the consumers of the device have
+probed, the device's driver can synchronize the hardware state of the device to
+match the aggregated software state requested by all the consumers. Hence the
+name sync_state().
+
+While obvious examples of resources that can benefit from sync_state() include
+resources such as regulator, sync_state() can also be useful for complex
+resources like IOMMUs. For example, IOMMUs with multiple consumers (devices
+whose addresses are remapped by the IOMMU) might need to keep their mappings
+fixed at (or additive to) the boot configuration until all its consumers have
+probed.
+
+While the typical use case for sync_state() is to have the kernel cleanly take
+over management of devices from the bootloader, the usage of sync_state() is
+not restricted to that. Use it whenever it makes sense to take an action after
+all the consumers of a device have probed.
+
int (*remove) (struct device *dev);
remove is called to unbind a driver from a device. This may be