linux-kernel - Re: [PATCH v5 3/4] PCI: Decouple D3Hot and D3Cold handling for bridges

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Message-ID: <20240821014559.GA236134@bhelgaas>
Date: Tue, 20 Aug 2024 20:45:59 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: manivannan.sadhasivam@...aro.org
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	lukas@...ner.de, mika.westerberg@...ux.intel.com,
	Hsin-Yi Wang <hsinyi@...omium.org>
Subject: Re: [PATCH v5 3/4] PCI: Decouple D3Hot and D3Cold handling for
 bridges

On Fri, Aug 02, 2024 at 11:25:02AM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> 
> Currently, there is no proper distinction between D3Hot and D3Cold while
> handling the power management for PCI bridges. For instance,
> pci_bridge_d3_allowed() API decides whether it is allowed to put the
> bridge in D3, but it doesn't explicitly specify whether D3Hot or D3Cold
> is allowed in a scenario. This often leads to confusion and may be prone
> to errors.
> 
> So let's split the D3Hot and D3Cold handling where possible. The current
> pci_bridge_d3_allowed() API is now split into pci_bridge_d3hot_allowed()
> and pci_bridge_d3cold_allowed() APIs and used in relevant places.

s/So let's split/Split/

> Also, pci_bridge_d3_update() API is now renamed to
> pci_bridge_d3cold_update() since it was only used to check the possibility
> of D3Cold.
> 
> Note that it is assumed that only D3Hot needs to be checked while
> transitioning the bridge during runtime PM and D3Cold in other places. In
> the ACPI case, wakeup is now only enabled if both D3Hot and D3Cold are
> allowed for the bridge.
> 
> Still, there are places where just 'd3' is used opaquely, but those are
> hard to distinguish, hence left for future cleanups.

The spec does use "D3Hot/D3Cold" (with Hot/Cold capitalized and
subscripted), but most Linux doc and comments use "D3hot" and
"D3cold", so I think we should stick with the Linux convention (it's
not 100%, but it's a pretty big majority).

> -	if (pci_dev->bridge_d3_allowed)
> +	if (pci_dev->bridge_d3cold_allowed && pci_dev->bridge_d3hot_allowed)

Much of this patch is renames that could be easily reviewed.  But
there are a few things like this that are not simple renames.  Can you
split out these non-rename things to their own patch(es) with their
own explanations?

Bjorn