linux-kernel - Re: [PATCH V2] PCI: Fix PCI bridges not to go to D3Hot on SPARC64

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Message-Id: <20251203.211612.2136559080137113794.rene@exactco.de>
Date: Wed, 03 Dec 2025 21:16:12 +0100 (CET)
From: René Rebe <rene@...ctco.de>
To: glaubitz@...sik.fu-berlin.de
Cc: linux-pci@...r.kernel.org, rafael@...nel.org,
 mika.westerberg@...ux.intel.com, lukas@...ner.de,
 briannorris@...omium.org, helgaas@...nel.org,
 linux-kernel@...r.kernel.org, riccardo.mottola@...ero.it, mani@...nel.org,
 mario.limonciello@....com
Subject: Re: [PATCH V2] PCI: Fix PCI bridges not to go to D3Hot on SPARC64

On Wed, 03 Dec 2025 20:31:58 +0100, John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de> wrote:

> Hi Rene,
> 
> On Wed, 2025-12-03 at 20:05 +0100, René Rebe wrote:
> > Commit a5fb3ff63287 ("PCI: Allow PCI bridges to go to D3Hot on all
> > non-x86") was bisected to break some SPARC64 systems, see two oopses
> > below. Fix by not allowing D3Hot on sparc64 while this is being
> > further analyzed.
> 
> I think your summary is still misleading as at least to me it sounds
> like you are providing a patch that fixes the D3Hot state on SPARC64
> while in reality you're actually blacklisting the D3 power state on
> the platform.
> 
> I suggest something like:
> 
> "pci: Don't allow D3 power state on sparc64"

But, my subject was exactly "Fix PCI bridges _not to go to D3Hot on SPARC64_"

and the text says:

Fix (this commit regression) by _not allowing D3Hot on sparc64_

I would rather move on debugging this, ...

  René

> This would also match the description of pci_bridge_d3_possible():
> 
> /**
>  * pci_bridge_d3_possible - Is it possible to put the bridge into D3
>  * @bridge: Bridge to check
>  *
>  * Currently we only allow D3 for some PCIe ports and for Thunderbolt.
>  *
>  * Return: Whether it is possible to move the bridge to D3.
>  *
>  * The return value is guaranteed to be constant across the entire lifetime
>  * of the bridge, including its hot-removal.
>  */
> 
> The function pci_bridge_d3_possible() determines whether D3 is allowed
> on a certain platform and by adding CONFIG_SPARC64 to the list, you are
> explicitly disallowing the use of this power state.
> 
> Adrian
> 
> -- 
>  .''`.  John Paul Adrian Glaubitz
> : :' :  Debian Developer
> `. `'   Physicist
>   `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

-- 
René Rebe, ExactCODE GmbH, Berlin, Germany
https://exactco.de • https://t2linux.com • https://patreon.com/renerebe