linux-kernel - [PATCH v2 0/3] pmdomain: ti_sci: collect and send low-power mode constraints

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Message-Id: <20240819-lpm-v6-10-constraints-pmdomain-v2-0-461325a6008f@baylibre.com>
Date: Mon, 19 Aug 2024 17:00:10 -0700
From: Kevin Hilman <khilman@...libre.com>
To: Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org
Cc: Nishanth Menon <nm@...com>, Vibhore Vardhan <vibhore@...com>, 
 Dhruva Gole <d-gole@...com>, Akashdeep Kaur <a-kaur@...com>, 
 Sebin Francis <sebin.francis@...com>, 
 Markus Schneider-Pargmann <msp@...libre.com>, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/3] pmdomain: ti_sci: collect and send low-power mode
 constraints

The latest (10.x) version of the firmware for the PM co-processor (aka
device manager, or DM) adds support for a "managed" mode, where the DM
firmware will select the specific low power state which is entered
when Linux requests a system-wide suspend.

In this mode, the DM will always attempt the deepest low-power state
available for the SoC.

However, Linux (or OSes running on other cores) may want to constrain
the DM for certain use cases.  For example, the deepest state may have
a wakeup/resume latency that is too long for certain use cases.  Or,
some wakeup-capable devices may potentially be powered off in deep
low-power states, but if one of those devices is enabled as a wakeup
source, it should not be powered off.

These kinds of constraints are are already known in Linux by the use
of existing APIs such as per-device PM QoS and device wakeup APIs, but
now we need to communicate these constraints to the DM.

For TI SoCs with TI SCI support, all DM-managed devices will be
connected to a TI SCI PM domain.  So the goal of this series is to use
the PM domain driver for TI SCI devices to collect constraints, and
communicate them to the DM via the new TI SCI APIs.

This is all managed by TI SCI PM domain code.  No new APIs are needed
by Linux drivers.  Any device that is managed by TI SCI will be
checked for QoS constraints or wakeup capability and the constraints
will be collected and sent to the DM.

This series depends on the support for the new TI SCI APIs (v10) and
was also tested with this series to update 8250_omap serial support
for AM62x[2].

[1] https://lore.kernel.org/all/20240801195422.2296347-1-msp@baylibre.com
[2] https://lore.kernel.org/all/20240807141227.1093006-1-msp@baylibre.com/

Signed-off-by: Kevin Hilman <khilman@...libre.com>
---
Changes in v2:

- To simplify this version a bit, drop the pmdomain ->power_off()
  changes.  Constraints only sent during ->suspend() path.  The pmdomain
  path was an optimization that may be added back later.
- With the above simplification, drop the extra state variables that
  had been added to keep track of constraint status.
- Link to v1: https://lore.kernel.org/r/20240805-lpm-v6-10-constraints-pmdomain-v1-0-d186b68ded4c@baylibre.com

---
Kevin Hilman (3):
      pmdomain: ti_sci: add per-device latency constraint management
      pmdomain: ti_sci: add wakeup constraint management
      pmdomain: ti_sci: handle wake IRQs for IO daisy chain wakeups

 drivers/pmdomain/ti/ti_sci_pm_domains.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
---
base-commit: ad7eb1b6b92ee0c959a0a6ae846ddadd7a79ea64
change-id: 20240802-lpm-v6-10-constraints-pmdomain-f33df5aef449

Best regards,
-- 
Kevin Hilman <khilman@...libre.com>