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From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: adrianhoyin.ng@altera.com, dinguyen@kernel.org, Frank.Li@nxp.com,
	linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] i3c: dw: add option to disable runtime PM for DesignWare I3C controller
Date: Thu, 30 Oct 2025 18:09:29 +0100	[thread overview]
Message-ID: <20251030170929b5991b7d@mail.local> (raw)
In-Reply-To: <aPCg0bFm4-DnmhAp@shikoro>

On 16/10/2025 09:37:53+0200, Wolfram Sang wrote:
> 
> > > Add a new Kconfig option, DW_I3C_DISABLE_RUNTIME_PM, that allows
> > > disabling all runtime power management (PM) operations for the
> > > Synopsys DesignWare I3C controller. When this option is selected,
> > > the driver skips all runtime PM calls such as pm_runtime_enable(),
> > > pm_runtime_get(), and pm_runtime_put(), keeping the controller
> > > permanently active.
> > 
> > While the quirk may make sense, it definitively can't be activated by a
> > Kconfig option. This should rather be tied to a new compatible string or
> > a property.
> 
> I wondered why this is a quirk, at all, and not default behaviour. Is it
> because it works with some RPM implementations and not with others,
> depending on the platform?
> 
> But even if that is the case, it might be worth to opt-in for power
> management instead of opting-out for buggy behaviour. Because I would
> not assume that IBI have been thoroughly tested when a new platform
> using this driver gets upstream. So, the buggy behaviour may only be
> recognized later. Or?
> 

I guess it depends on how the IP has been integrated on the SoC, hence
my suggestion to tie this to a compatible string. opt-in or opt-out, I
don't care too much but seeing this seems to work for AMD, we need to
keep the existing behaviour for them.


-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

-- 
linux-i3c mailing list
linux-i3c@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-i3c

WARNING: multiple messages have this Message-ID (diff)
From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: adrianhoyin.ng@altera.com, dinguyen@kernel.org, Frank.Li@nxp.com,
	linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] i3c: dw: add option to disable runtime PM for DesignWare I3C controller
Date: Thu, 30 Oct 2025 18:09:29 +0100	[thread overview]
Message-ID: <20251030170929b5991b7d@mail.local> (raw)
In-Reply-To: <aPCg0bFm4-DnmhAp@shikoro>

On 16/10/2025 09:37:53+0200, Wolfram Sang wrote:
> 
> > > Add a new Kconfig option, DW_I3C_DISABLE_RUNTIME_PM, that allows
> > > disabling all runtime power management (PM) operations for the
> > > Synopsys DesignWare I3C controller. When this option is selected,
> > > the driver skips all runtime PM calls such as pm_runtime_enable(),
> > > pm_runtime_get(), and pm_runtime_put(), keeping the controller
> > > permanently active.
> > 
> > While the quirk may make sense, it definitively can't be activated by a
> > Kconfig option. This should rather be tied to a new compatible string or
> > a property.
> 
> I wondered why this is a quirk, at all, and not default behaviour. Is it
> because it works with some RPM implementations and not with others,
> depending on the platform?
> 
> But even if that is the case, it might be worth to opt-in for power
> management instead of opting-out for buggy behaviour. Because I would
> not assume that IBI have been thoroughly tested when a new platform
> using this driver gets upstream. So, the buggy behaviour may only be
> recognized later. Or?
> 

I guess it depends on how the IP has been integrated on the SoC, hence
my suggestion to tie this to a compatible string. opt-in or opt-out, I
don't care too much but seeing this seems to work for AMD, we need to
keep the existing behaviour for them.


-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

  reply	other threads:[~2025-10-30 17:09 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-10-16  2:03 [RFC PATCH] i3c: dw: add option to disable runtime PM for DesignWare I3C controller adrianhoyin.ng
2025-10-16  2:03 ` adrianhoyin.ng
2025-10-16  7:10 ` Alexandre Belloni
2025-10-16  7:10   ` Alexandre Belloni
2025-10-16  7:37   ` Wolfram Sang
2025-10-16  7:37     ` Wolfram Sang
2025-10-30 17:09     ` Alexandre Belloni [this message]
2025-10-30 17:09       ` Alexandre Belloni

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