linux-kernel - Re: [RFC PATCH v2 0/2] Extend mmio-mux driver to configure mux with new DT property

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Message-ID: <2e80f6bc-2fb0-4f0d-9450-cbcf4dddca66@ti.com>
Date: Fri, 30 May 2025 22:35:24 +0530
From: "Vankar, Chintan" <c-vankar@...com>
To: Conor Dooley <conor+dt@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Rob Herring <robh@...nel.org>, Peter Rosin
	<peda@...ntia.se>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: <s-vadapalli@...com>, <danishanwar@...com>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Vignesh
 Raghavendra <vigneshr@...com>,
        Nishanth Menon <nm@...com>, Thomas Gleixner
	<tglx@...utronix.de>
Subject: Re: [RFC PATCH v2 0/2] Extend mmio-mux driver to configure mux with
 new DT property

Hello Greg,

I have tried to implement Timesync Router node to the suitable
Subsystems (Interrupt controller and Mux-controller). Thomas
has provided a feedback with a reason why Timesync Router is not
suitable for irqchip. But I didn't get a proper feedback for mux-
controller subsystem.

Can you please help me deciding in which subsystem I should implement
it, if not mux-controller can it go in drivers/misc ?

Regards,
Chintan.

On 5/20/2025 10:59 AM, Chintan Vankar wrote:
> Hello Peter,
> 
> I am trying to implement a driver for hardware module called Timesync
> Router which is present on almost all the SoCs of Texas Instruments and
> I need your advise to implement it.
> 
> Timesync Router provides a mechanism to mux M input to N outputs, where
> all M inputs are selectable to be driven per N output.
> 
>                           ________________________
>                          |    Timesync INTR       +---->dma_local_events
>                          |                        |
>   Device sync events----->                        +---->pcie_cpts_hw_push
>                          |                        |
>            cpts_genf----->                        +---->cpts_hw_push
>                          |________________________|
> 
> 
> Diagram shows a very concise view of Timesync Router. It receives
> signals from multiple modules and routes the same on the other side. To
> configure the functionality, we need to program output registers of
> Timesync Router to configure it with the input signal. One of the
> application of Timesync Router is to generate a PPS signal for CPTS
> module. Timesync Router receives periodic signals generated by CPTS
> module as shown "cpts_genf" in diagram and it can be routed via Timesync
> Router as a Hardware Push Events as shown "cpts_hw_push" in diagram.
> 
> The functionality of Timesync Router seems very much identical to the
> mux-controller, specifically mmio driver present in the mux subsystem.
> I have also posted a detailed explanation on how can we modify mmio
> driver which can work as a generic driver for the hardware module
> identical to Timesync Router at here:
> https://lore.kernel.org/r/1ce1fc6b-fc16-4fb7-9f68-57b495aa5eae@ti.com/
> 
> I have also tried to implement this module with irq subsystem:
> https://lore.kernel.org/r/20250205160119.136639-1-c-vankar@ti.com/, for
> which I received a response from the Thomas Gleixner that why it cannot
> be included in the irq subsystem:
> https://lore.kernel.org/r/87ikp8jph9.ffs@tglx/.
> 
> After receiving feedback on the Interrupt Router implementation, I tried
> to implement it as a mux-controller which seems more relevant subsystem
> for Timesync Router. Can you please advise me whether it can be included
> in the mux-controller subsystem or not ?
> 
> Regards,
> Chintan.
> 
> 
> 
> 
> On 04/03/25 15:53, Chintan Vankar wrote:
>> This series extends mmio-mux driver's capability to configure driver in
>> with extended property.
>>
>> In current driver implementation, driver is parsing register's offset,
>> mask and value from two different device tree property which makes it
>> complex to specify a specific register or set of registers. Introducing
>> mux-reg-masks-states will make it easier to specify the same values for
>> particular register or set of registers.
>>
>> This series is based on linux next tagged next-20250303.
>>
>> Link to v1:
>> https://lore.kernel.org/r/20250227202206.2551305-1-c-vankar@ti.com/
>>
>> Changes from v1 to v2:
>> - Updated dt-bindings for the required conditions as suggested by Conor
>>    Dooley and Andrew Davis.
>> - Modified driver changes as pointed out by Andrew Davis.
>>
>> Chintan Vankar (2):
>>    devicetree: bindings: mux: reg-mux: Update bindings for reg-mux for
>>      new property
>>    mux: mmio: Extend mmio-mux driver to configure mux with new DT
>>      property
>>
>>   .../devicetree/bindings/mux/reg-mux.yaml      |  28 +++-
>>   drivers/mux/mmio.c                            | 144 ++++++++++++++----
>>   2 files changed, 141 insertions(+), 31 deletions(-)
>>