Re: [PATCH v8 0/3] firmware: ti_sci: Partial-IO support

["Markus Schneider-Pargmann" <msp@baylibre.com>]

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Hi Nishanth,

On Wed Oct 1, 2025 at 7:00 PM CEST, Nishanth Menon wrote:
> On 16:37-20251001, Markus Schneider-Pargmann (TI.com) wrote:
>> Hi,
>> 
>> This series adds support for Partial-IO to the ti-sci driver,
>> implementing the firmware interface necessary to enter this low power
>> state. It processes the wakeup-source properties from the devicetree and
>> communicates with the system firmware to enter Partial-IO mode when
>> appropriate wakeup sources are enabled.
>> 
>> Partial-IO Overview
>> ------------------
>> Partial-IO is a low power system state in which nearly everything is
>> turned off except the pins of the CANUART group (mcu_mcan0, mcu_mcan1,
>> wkup_uart0 and mcu_uart0). These devices can trigger a wakeup of the
>> system on pin activity. Note that this does not resume the system as the
>> DDR is off as well. So this state can be considered a power-off state
>> with wakeup capabilities.
>> 
>> A documentation can also be found in section 6.2.4 in the TRM:
>>   https://www.ti.com/lit/pdf/spruiv7
>> 
>> Implementation Details
>> ----------------------
>> The complete Partial-IO feature requires three coordinated series, each
>> handling a different aspect of the implementation:
>> 
>> 1. m_can driver series: Implements device-specific wakeup functionality
>>    for m_can devices, allowing them to be set as wakeup sources.
>>    https://gitlab.baylibre.com/msp8/linux/-/tree/topic/mcan-wakeup-source/v6.17?ref_type=heads
>>    https://lore.kernel.org/r/20250812-topic-mcan-wakeup-source-v6-12-v8-0-6972a810d63b@baylibre.com
>> 
>> 2. Devicetree series: Defines system states and wakeup sources in the
>>    devicetree for am62, am62a and am62p.
>>    https://gitlab.baylibre.com/msp8/linux/-/tree/topic/am62-dt-partialio/v6.17?ref_type=heads
>>    https://lore.kernel.org/r/20250812-topic-am62-dt-partialio-v6-15-v2-0-25352364a0ac@baylibre.com
>> 
>> 3. This series (TI-SCI firmware): Implements the firmware interface to
>>    enter Partial-IO mode when appropriate wakeup sources are enabled.
>
> If this is the order of dependencies, I guess the series has to wait
> till CAN driver changes are merged? did I get that right?

Yes, the series has to wait for the m_can series as it containts the
dt-binding required for this series to work.

>
> Also surprised that the DT series is second in the dependency.. usually
> dts changes occur the last. but anyways..

Yes, true, they could be switched as well. The driver changes of course
won't work as long as the DT series is not merged, but they could be
merged in parallel as well. Neither the DT series nor this series modify
any bindings. Only the mcan series does.

Best
Markus

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