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From: Tony Lindgren <tony@atomide.com>
To: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Cc: Rob Herring <robh+dt@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Olof Johansson <olof@lixom.net>,
	soc@kernel.org, Vignesh Raghavendra <vigneshr@ti.com>,
	Tero Kristo <kristo@kernel.org>,
	jan.kiszka@siemens.com, linux-arm-kernel@lists.infradead.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	Nishanth Menon <nm@ti.com>
Subject: Re: [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional peripherals by default
Date: Mon, 7 Feb 2022 13:25:14 +0200	[thread overview]
Message-ID: <YgEBml9HvFzSl289@atomide.com> (raw)
In-Reply-To: <5944ba0ce568eaf507917799b1dfd89a3d0ca492.camel@ew.tq-group.com>

* Matthias Schiffer <matthias.schiffer@ew.tq-group.com> [220207 08:45]:
> Generally I think that it's a bootloader's responsiblity to disable
> unneeded devices - the kernel may not even have a driver for some
> peripherals, leading to the same behaviour as a "disabled" status. For
> this reason I believe that it should always be okay to set unneeded
> devices to "disabled", and it should be considered a safe default.

Not possible, think kexec for example :) How would the previous kernel
even know what to disable if Linux has no idea about the devices?

If there are issues you're seeing, it's likely a bug in some of the
device drivers for not checking for the necessary resources like
pinctrl for i2c lines.

> I'm not sure what the consensus on these issues is. I'm more familiar
> with NXP's i.MX and Layerscape SoCs, where it's common to have all
> muxable peripherals set to "disabled" in the base DTSI, and a quick
> grep through a few dts directories gives me the impression that this is
> the case for most other vendors as well.

This approach only works for SoCs that don't need the kernel to idle
devices for runtime PM.

Regards,

Tony

WARNING: multiple messages have this Message-ID (diff)
From: Tony Lindgren <tony@atomide.com>
To: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Cc: Rob Herring <robh+dt@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Olof Johansson <olof@lixom.net>,
	soc@kernel.org, Vignesh Raghavendra <vigneshr@ti.com>,
	Tero Kristo <kristo@kernel.org>,
	jan.kiszka@siemens.com, linux-arm-kernel@lists.infradead.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	Nishanth Menon <nm@ti.com>
Subject: Re: [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional peripherals by default
Date: Mon, 7 Feb 2022 13:25:14 +0200	[thread overview]
Message-ID: <YgEBml9HvFzSl289@atomide.com> (raw)
In-Reply-To: <5944ba0ce568eaf507917799b1dfd89a3d0ca492.camel@ew.tq-group.com>

* Matthias Schiffer <matthias.schiffer@ew.tq-group.com> [220207 08:45]:
> Generally I think that it's a bootloader's responsiblity to disable
> unneeded devices - the kernel may not even have a driver for some
> peripherals, leading to the same behaviour as a "disabled" status. For
> this reason I believe that it should always be okay to set unneeded
> devices to "disabled", and it should be considered a safe default.

Not possible, think kexec for example :) How would the previous kernel
even know what to disable if Linux has no idea about the devices?

If there are issues you're seeing, it's likely a bug in some of the
device drivers for not checking for the necessary resources like
pinctrl for i2c lines.

> I'm not sure what the consensus on these issues is. I'm more familiar
> with NXP's i.MX and Layerscape SoCs, where it's common to have all
> muxable peripherals set to "disabled" in the base DTSI, and a quick
> grep through a few dts directories gives me the impression that this is
> the case for most other vendors as well.

This approach only works for SoCs that don't need the kernel to idle
devices for runtime PM.

Regards,

Tony

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-02-07 11:25 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-03 14:02 [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional peripherals by default Matthias Schiffer
2022-02-03 14:02 ` Matthias Schiffer
2022-02-03 14:02 ` [PATCH v2 2/2] arm64: dts: ti: k3-am65*: remove #address-cells/#size-cells from flash nodes Matthias Schiffer
2022-02-03 14:02   ` Matthias Schiffer
2022-02-04 14:31 ` [PATCH v2 1/2] arm64: dts: ti: k3-am65: disable optional peripherals by default Nishanth Menon
2022-02-04 14:31   ` Nishanth Menon
2022-02-07  6:54   ` Tony Lindgren
2022-02-07  6:54     ` Tony Lindgren
2022-02-07  8:45     ` Matthias Schiffer
2022-02-07  8:45       ` Matthias Schiffer
2022-02-07 11:25       ` Tony Lindgren [this message]
2022-02-07 11:25         ` Tony Lindgren
2022-02-08 10:53         ` Matthias Schiffer
2022-02-08 10:53           ` Matthias Schiffer
2022-02-08 11:52           ` Tony Lindgren
2022-02-08 11:52             ` Tony Lindgren
2022-02-28 10:30             ` Matthias Schiffer
2022-02-28 10:30               ` Matthias Schiffer
2022-03-09  9:11               ` Tony Lindgren
2022-03-09  9:11                 ` Tony Lindgren
2022-03-09 11:10                 ` Matthias Schiffer
2022-03-09 11:10                   ` Matthias Schiffer
2022-03-09 14:03                   ` Tony Lindgren
2022-03-09 14:03                     ` Tony Lindgren
2022-02-16 16:40 ` (subset) " Nishanth Menon
2022-02-16 16:40   ` Nishanth Menon

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