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[v4,0/3] clk: qcom: Add support for multiple power-domains for a clock controller.

Message ID 20241127-b4-linux-next-24-11-18-clock-multiple-power-domains-v4-0-4348d40cb635@linaro.org
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Series clk: qcom: Add support for multiple power-domains for a clock controller. | expand

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Bryan O'Donoghue Nov. 27, 2024, 3:53 p.m. UTC 
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-linux-next-24-11-18-clock-multiple-power-domains-v3-0-836dad33521a@linaro.org

v3:
- Fixes commit log "per which" - Bryan 
- Link to v2: https://lore.kernel.org/r/20241125-b4-linux-next-24-11-18-clock-multiple-power-domains-v2-0-a5e7554d7e45@linaro.org

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-linux-next-24-11-18-clock-multiple-power-domains-v1-0-b7a2bd82ba37@linaro.org

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 <bryan.odonoghue@linaro.org>
---
Bryan O'Donoghue (3):
      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 | 21 +++++++++++++++++++++
 drivers/clk/qcom/gdsc.c   | 41 +++++++++++++++++++++++++++++++++++++++--
 drivers/clk/qcom/gdsc.h   |  1 +
 3 files changed, 61 insertions(+), 2 deletions(-)
---
base-commit: 744cf71b8bdfcdd77aaf58395e068b7457634b2c
change-id: 20241118-b4-linux-next-24-11-18-clock-multiple-power-domains-a5f994dc452a

Best regards,