[v10,0/4] clk: qcom: Add support for multiple power-domains for a clock controller.

Message

Bryan O'Donoghue Jan. 17, 2025, 1:54 p.m. UTC

Changes in v10:
- Updated the commit log of patch #1 to make the reasoning - that it makes
  applying the subsequent patch cleaner/nicer clear - Bjorn
- Substantially rewrites final patch commit to mostly reflect Bjorn's
  summation of my long and rambling previous paragraphs.
  Being a visual person, I've included some example pseudo-code which
  hopefully makes the intent clearer plus some ASCII art >= Klimt.
- Link to v9: https://lore.kernel.org/r/20241230-b4-li[e-mail]

Changes in v9:
- Added patch to unwind pm subdomains in reverse order.
  It would also be possible to squash this patch into patch#2 but,
  my own preference is for more granular patches like this instead of
  "slipping in" functional changes in larger patches like #2. - bod
- Unwinding pm subdomain on error in patch #2.
  To facilitate this change patch #1 was created - Vlad
- Drops Bjorn's RB on patch #2. There is a small churn in this patch
  but enough that a reviewer might reasonably expect RB to be given again.
- Amends commit log for patch #3 further.
  v8 added a lot to the commit log to provide further information but, it
  is clear from the comments I received on the commit log that the added
  verbiage was occlusive not elucidative.
  Reduce down the commit log of patch #3 - especially Q&A item #1.
  Sometimes less is more.
- Link to v8: https://lore.kernel.org/r/20241211-b4-li[e-mail]

Changes in v8:
- Picks up change I agreed with Vlad but failed to cherry-pick into my b4
  tree - Vlad/Bod
- Rewords the commit log for patch #3. As I read it I decided I might
  translate bits of it from thought-stream into English - Bod
- Link to v7: https://lore.kernel.org/r/20241211-b4-li[e-mail]

Changes in v7:
- Expand commit log in patch #3
  I've discussed with Bjorn on IRC and video what to put into the log here
  and captured most of what we discussed.

  Mostly the point here is voting for voltages in the power-domain list
  is up to the drivers to do with performance states/opp-tables not for the
  GDSC code. - Bjorn/Bryan
- Link to v6: https://lore.kernel.org/r/20241129-b4-li[e-mail]

Changes in v6:
- Passes NULL to second parameter of devm_pm_domain_attach_list - Vlad
- Link to v5: https://lore.kernel.org/r/20241128-b4-li[e-mail]

Changes in v5:
- In-lines devm_pm_domain_attach_list() in probe() directly - Vlad
- Link to v4: https://lore.kernel.org/r/20241127-b4-li[e-mail]

v4:
- Adds Bjorn's RB to first patch - Bjorn
- Drops the 'd' in "and int" - Bjorn
- Amends commit log of patch 3 to capture a number of open questions -
  Bjorn
- Link to v3: https://lore.kernel.org/r/20241126-b4-li[e-mail]

v3:
- Fixes commit log "per which" - Bryan
- Link to v2: https://lore.kernel.org/r/20241125-b4-li[e-mail]

v2:
The main change in this version is Bjorn's pointing out that pm_runtime_*
inside of the gdsc_enable/gdsc_disable path would be recursive and cause a
lockdep splat. Dmitry alluded to this too.

Bjorn pointed to stuff being done lower in the gdsc_register() routine that
might be a starting point.

I iterated around that idea and came up with patch #3. When a gdsc has no
parent and the pd_list is non-NULL then attach that orphan GDSC to the
clock controller power-domain list.

Existing subdomain code in gdsc_register() will connect the parent GDSCs in
the clock-controller to the clock-controller subdomain, the new code here
does that same job for a list of power-domains the clock controller depends
on.

To Dmitry's point about MMCX and MCX dependencies for the registers inside
of the clock controller, I have switched off all references in a test dtsi
and confirmed that accessing the clock-controller regs themselves isn't
required.

On the second point I also verified my test branch with lockdep on which
was a concern with the pm_domain version of this solution but I wanted to
cover it anyway with the new approach for completeness sake.

Here's the item-by-item list of changes:

- Adds a patch to capture pm_genpd_add_subdomain() result code - Bryan
- Changes changelog of second patch to remove singleton and generally
  to make the commit log easier to understand - Bjorn
- Uses demv_pm_domain_attach_list - Vlad
- Changes error check to if (ret < 0 && ret != -EEXIST) - Vlad
- Retains passing &pd_data instead of NULL - because NULL doesn't do
  the same thing - Bryan/Vlad
- Retains standalone function qcom_cc_pds_attach() because the pd_data
  enumeration looks neater in a standalone function - Bryan/Vlad
- Drops pm_runtime in favour of gdsc_add_subdomain_list() for each
  power-domain in the pd_list.
  The pd_list will be whatever is pointed to by power-domains = <>
  in the dtsi - Bjorn
- Link to v1: https://lore.kernel.org/r/20241118-b4-li[e-mail]

v1:
On x1e80100 and it's SKUs the Camera Clock Controller - CAMCC has
multiple power-domains which power it. Usually with a single power-domain
the core platform code will automatically switch on the singleton
power-domain for you. If you have multiple power-domains for a device, in
this case the clock controller, you need to switch those power-domains
on/off yourself.

The clock controllers can also contain Global Distributed
Switch Controllers - GDSCs which themselves can be referenced from dtsi
nodes ultimately triggering a gdsc_en() in drivers/clk/qcom/gdsc.c.

As an example:

cci0: cci@ac4a000 {
	power-domains = <&camcc TITAN_TOP_GDSC>;
};

This series adds the support to attach a power-domain list to the
clock-controllers and the GDSCs those controllers provide so that in the
case of the above example gdsc_toggle_logic() will trigger the power-domain
list with pm_runtime_resume_and_get() and pm_runtime_put_sync()
respectively.

Signed-off-by: Bryan O'Donoghue <[e-mail]>
---
Bryan O'Donoghue (4):
      clk: qcom: gdsc: Release pm subdomains in reverse add order
      clk: qcom: gdsc: Capture pm_genpd_add_subdomain result code
      clk: qcom: common: Add support for power-domain attachment
      clk: qcom: Support attaching GDSCs to multiple parents

 drivers/clk/qcom/common.c |  6 ++++
 drivers/clk/qcom/gdsc.c   | 75 +++++++++++++++++++++++++++++++++++++++--------
 drivers/clk/qcom/gdsc.h   |  1 +
 3 files changed, 69 insertions(+), 13 deletions(-)
---
base-commit: 0907e7fb35756464aa34c35d6abb02998418164b
change-id: 20241118-b4-linux-next-24-11-18-clock-multiple-power-domains-a5f994dc452a

Best regards,