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  1. 02 4月, 2021 1 次提交
  3. 19 2月, 2021 1 次提交
  5. 09 2月, 2021 3 次提交
  7. 26 1月, 2021 2 次提交
  9. 10 12月, 2020 2 次提交
  11. 28 7月, 2020 2 次提交
  13. 01 7月, 2020 1 次提交
  15. 18 6月, 2020 1 次提交
    • S
      of: property: Improve cycle detection when one of the devices is never added · bb278b14
      由 Saravana Kannan 提交于 
      Consider this example where -> means LHS device is a consumer of RHS
device and indentation represents "child of" of the previous device.

Device A -> Device C

Device B -> Device A
	Device C

Without this commit:
1. Device A is added.
2. Device A is added to waiting for supplier list (Device C)
3. Device B is added
4. Device B is linked as a consumer to Device A
5. Device A doesn't probe because it's waiting for Device C to be added.
6. Device B doesn't probe because Device A hasn't probed.
7. Device C will never be added because it's parent hasn't probed.

So, Device A, B and C will be in a probe/add deadlock.

This commit detects this scenario and stops trying to create a device
link between Device A and Device C since doing so would create the
following cycle:
Device A -> Devic C -(parent)-> Device B -> Device A.

With this commit:
1. Device A is added.
3. Device B is added
4. Device B is linked as a consumer to Device A
5. Device A probes.
6. Device B probes because Device A has probed.
7. Device C is added and probed.
Signed-off-by: NSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200610011934.49795-3-saravanak@google.comSigned-off-by: NRob Herring <robh@kernel.org>
      bb278b14
  17. 29 4月, 2020 3 次提交
  19. 15 4月, 2020 1 次提交
  21. 05 3月, 2020 2 次提交
  23. 26 2月, 2020 1 次提交
  25. 22 11月, 2019 1 次提交
  27. 21 11月, 2019 2 次提交
  29. 15 11月, 2019 1 次提交
  31. 07 11月, 2019 3 次提交
  33. 03 11月, 2019 2 次提交
  35. 17 10月, 2019 1 次提交
  37. 11 10月, 2019 2 次提交
  39. 04 10月, 2019 2 次提交
    • S
      of: property: Create device links for all child-supplier depencencies · d4387cd1
      由 Saravana Kannan 提交于 
      A parent device can have child devices that it adds when it probes. But
this probing of the parent device can happen way after kernel init is done
-- for example, when the parent device's driver is loaded as a module.

In such cases, if the child devices depend on a supplier in the system, we
need to make sure the supplier gets the sync_state() callback only after
these child devices are added and probed.

To achieve this, when creating device links for a device by looking at its
DT node, don't just look at DT references at the top node level. Look at DT
references in all the descendant nodes too and create device links from the
ancestor device to all these supplier devices.

This way, when the parent device probes and adds child devices, the child
devices can then create their own device links to the suppliers and further
delay the supplier's sync_state() callback to after the child devices are
probed.

Example:
In this illustration, -> denotes DT references and indentation
represents child status.

Device node A
	Device node B -> D
	Device node C -> B, D

Device node D

Assume all these devices have their drivers loaded as modules.

Without this patch, this is the sequence of events:
1. D is added.
2. A is added.
3. Device D probes.
4. Device D gets its sync_state() callback.
5. Device B and C might malfunction because their resources got
   altered/turned off before they can make active requests for them.

With this patch, this is the sequence of events:
1. D is added.
2. A is added and creates device links to D.
3. Device link from A to B is not added because A is a parent of B.
4. Device D probes.
5. Device D does not get it's sync_state() callback because consumer A
   hasn't probed yet.
5. Device A probes.
5. a. Devices B and C are added.
5. b. Device links from B and C to D are added.
5. c. Device A's probe completes.
6. Device D does not get it's sync_state() callback because consumer A
   has probed but consumers B and C haven't probed yet.
7. Device B and C probe.
8. Device D gets it's sync_state() callback because all its consumers
   have probed.
9. None of the devices malfunction.
Signed-off-by: NSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-7-saravanak@google.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      d4387cd1
    • S
      of: property: Add functional dependency link from DT bindings · a3e1d1a7
      由 Saravana Kannan 提交于 
      Add device links after the devices are created (but before they are
probed) by looking at common DT bindings like clocks and
interconnects.

Automatically adding device links for functional dependencies at the
framework level provides the following benefits:

- Optimizes device probe order and avoids the useless work of
  attempting probes of devices that will not probe successfully
  (because their suppliers aren't present or haven't probed yet).

  For example, in a commonly available mobile SoC, registering just
  one consumer device's driver at an initcall level earlier than the
  supplier device's driver causes 11 failed probe attempts before the
  consumer device probes successfully. This was with a kernel with all
  the drivers statically compiled in. This problem gets a lot worse if
  all the drivers are loaded as modules without direct symbol
  dependencies.

- Supplier devices like clock providers, interconnect providers, etc
  need to keep the resources they provide active and at a particular
  state(s) during boot up even if their current set of consumers don't
  request the resource to be active. This is because the rest of the
  consumers might not have probed yet and turning off the resource
  before all the consumers have probed could lead to a hang or
  undesired user experience.

  Some frameworks (Eg: regulator) handle this today by turning off
  "unused" resources at late_initcall_sync and hoping all the devices
  have probed by then. This is not a valid assumption for systems with
  loadable modules. Other frameworks (Eg: clock) just don't handle
  this due to the lack of a clear signal for when they can turn off
  resources. This leads to downstream hacks to handle cases like this
  that can easily be solved in the upstream kernel.

  By linking devices before they are probed, we give suppliers a clear
  count of the number of dependent consumers. Once all of the
  consumers are active, the suppliers can turn off the unused
  resources without making assumptions about the number of consumers.

By default we just add device-links to track "driver presence" (probe
succeeded) of the supplier device. If any other functionality provided
by device-links are needed, it is left to the consumer/supplier
devices to change the link when they probe.

kbuild test robot reported clang error about missing const
Reported-by: Nkbuild test robot <lkp@intel.com>
Signed-off-by: NSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20190904211126.47518-4-saravanak@google.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      a3e1d1a7
  41. 10 4月, 2019 1 次提交
  43. 17 1月, 2019 1 次提交
  45. 06 12月, 2018 1 次提交
  47. 12 2月, 2018 1 次提交
  49. 08 1月, 2018 1 次提交
  51. 13 12月, 2017 1 次提交