linux-kernel - Re: [PATCH v2 0/4] Add overlays to disable optional hardware in k3-am6xx-phycore-som boards

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Date: Mon, 3 Jun 2024 23:11:49 +0530
From: Vignesh Raghavendra <vigneshr@...com>
To: Nathan Morrisson <nmorrisson@...tec.com>, <nm@...com>, <kristo@...nel.org>,
        <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>
CC: <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <upstream@...ts.phytec.de>,
        <w.egorov@...tec.de>
Subject: Re: [PATCH v2 0/4] Add overlays to disable optional hardware in
 k3-am6xx-phycore-som boards

Hi Nathan,

On 29/05/24 04:21, Nathan Morrisson wrote:
> Add three overlays to disable the eth phy, rtc, and spi nor. These
> overlays will be used to disable device tree nodes for components
> that are optionally not populated.
> 
> v2:
>   - Add build time tests in makefile
> 
> Nathan Morrisson (4):
>   arm64: dts: ti: k3-am64-phycore-som: Add serial_flash label


>   arm64: dts: ti: k3-am6xx-phycore-som: Add overlay to disable eth phy
>   arm64: dts: ti: k3-am6xx-phycore-som: Add overlay to disable rtc
>   arm64: dts: ti: k3-am6xx-phycore-som: Add overlay to disabl spi nor
> 
>  arch/arm64/boot/dts/ti/Makefile               | 17 +++++++++++++++++
>  .../boot/dts/ti/k3-am64-phycore-som.dtsi      |  2 +-
>  .../ti/k3-am6xx-phycore-disable-eth-phy.dtso  | 19 +++++++++++++++++++
>  .../dts/ti/k3-am6xx-phycore-disable-rtc.dtso  | 15 +++++++++++++++
>  .../ti/k3-am6xx-phycore-disable-spi-nor.dtso  | 15 +++++++++++++++
>  5 files changed, 67 insertions(+), 1 deletion(-)

>  create mode 100644 arch/arm64/boot/dts/ti/k3-am6xx-phycore-disable-eth-phy.dtso
>  create mode 100644 arch/arm64/boot/dts/ti/k3-am6xx-phycore-disable-rtc.dtso
>  create mode 100644 arch/arm64/boot/dts/ti/k3-am6xx-phycore-disable-spi-nor.dtso
> 

I am not sure if this a common practice to have overlays to disable
missing components (at least I dont see such dtso in kernel). I would
like to see an what DT maintainers feel as such dtsos can explode in
numbers.

Is this something that U-Boot can detect and fix up for the Linux DT?

Unpopulated SPI flash and RTC should ideally not be an issue as drivers
would gracefully fail albeit with some sort of error msg.
Not so sure about Eth PHYs though.

Also, Are these dtso's mutually exclusive? ie can SoM have SPI flash but
not RTC, have RTC and SPI Flash but no ETH PHY?

-- 
Regards
Vignesh