netdev - Re: [PATCH 1/3] e1000e: Remove redundant runtime resume for ethtool

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Message-ID: <20240326143544.GY403975@kernel.org>
Date: Tue, 26 Mar 2024 14:35:44 +0000
From: Simon Horman <horms@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Zheng Yan <zheng.z.yan@...el.com>,
	Sasha Neftin <sasha.neftin@...el.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 1/3] e1000e: Remove redundant runtime resume for
 ethtool_ops

On Mon, Mar 25, 2024 at 05:29:49PM -0500, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> e60b22c5b7e5 ("e1000e: fix accessing to suspended device") added
> ethtool_ops.begin() and .complete(), which used pm_runtime_get_sync() to
> resume suspended devices before any ethtool_ops callback and allow suspend
> after it completed.
> 
> 3ef672ab1862 ("e1000e: ethtool unnecessarily takes device out of RPM
> suspend") removed ethtool_ops.begin() and .complete() and instead did
> pm_runtime_get_sync() only in the individual ethtool_ops callbacks that
> access device registers.
> 
> Subsequently, f32a21376573 ("ethtool: runtime-resume netdev parent before
> ethtool ioctl ops") added pm_runtime_get_sync() in the dev_ethtool() path,
> so the device is resumed before *any* ethtool_ops callback, as it was
> before 3ef672ab1862.
> 
> Remove most runtime resumes from ethtool_ops, which are now redundant
> because the resume has already been done by dev_ethtool().  This is
> essentially a revert of 3ef672ab1862 ("e1000e: ethtool unnecessarily takes
> device out of RPM suspend").
> 
> There are a couple subtleties:
> 
>   - Prior to 3ef672ab1862, the device was resumed only for the duration of
>     a single ethtool callback.  3ef672ab1862 changed e1000_set_phys_id() so
>     the device was resumed for ETHTOOL_ID_ACTIVE and remained resumed until
>     a subsequent callback for ETHTOOL_ID_INACTIVE.  Preserve that part of
>     3ef672ab1862 so the device will not be runtime suspended while in the
>     ETHTOOL_ID_ACTIVE state.
> 
>   - 3ef672ab1862 added "if (!pm_runtime_suspended())" in before reading the
>     STATUS register in e1000_get_settings().  This was racy and is now
>     unnecessary because dev_ethtool() has resumed the device already, so
>     revert that.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>

Reviewed-by: Simon Horman <horms@...nel.org>