linux-kernel - Re: [PATCH v2 2/5] arm64: dts: ti: k3-j7200: Configure pinctrl for timer IO pads

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Date:   Fri, 2 Jun 2023 10:11:40 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Udit Kumar <u-kumar1@...com>
Cc:     nm@...com, vigneshr@...com, kristo@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, conor+dt@...nel.org,
        m-chawdhry@...com, n-francis@...com
Subject: Re: [PATCH v2 2/5] arm64: dts: ti: k3-j7200: Configure pinctrl for
 timer IO pads

* Udit Kumar <u-kumar1@...com> [230601 09:38]:
> There are timer IO pads in the MCU domain, and in the MAIN domain. These
> pads can be muxed for the related timers.
> 
> There are timer IO control registers for input and output. The registers
> for CTRLMMR_TIMER*_CTRL and CTRLMMR_MCU_TIMER*_CTRL are used to control
> the input. The registers for CTCTRLMMR_TIMERIO*_CTRL and
> CTRLMMR_MCU_TIMERIO*_CTRL the output.
> 
> The multiplexing is documented in TRM "5.1.2.3.1.4 Timer IO Muxing Control
> Registers" and "5.1.3.3.1.5 Timer IO Muxing Control Registers", and the
> CASCADE_EN bit is documented in TRM "12.6.3.1 Timers Overview".
> 
> For chaining timers, the timer IO control registers also have a CASCADE_EN
> input bit in the CTRLMMR_TIMER*_CTRL in the registers. The CASCADE_EN bit
> muxes the previous timer output, or possibly and external TIMER_IO pad
> source, to the input clock of the selected timer instance for odd numered
> timers. For the even numbered timers, the CASCADE_EN bit does not do
> anything. The timer cascade input routing options are shown in TRM
> "Figure 12-3224. Timers Overview". For handling beyond multiplexing, the
> driver support for timer cascading should be likely be handled via the
> clock framework.
> 
> The MCU timer controls are also marked as reserved for
> usage by the MCU firmware.

Reviewed-by: Tony Lindgren <tony@...mide.com>