linux-kernel - Re: [PATCH v5 06/11] drm/radeon: Use RMW accessors for changing LNKCTL

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Message-ID: <20230821191256.GA365126@bhelgaas>
Date:   Mon, 21 Aug 2023 14:12:56 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Deucher, Alexander" <Alexander.Deucher@....com>
Cc:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dean Luick <dean.luick@...nelisnetworks.com>,
        Jonas Dreßler <verdre@...d.nl>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v5 06/11] drm/radeon: Use RMW accessors for changing
 LNKCTL

On Fri, Aug 18, 2023 at 04:12:57PM +0000, Deucher, Alexander wrote:
> > -----Original Message-----
> > From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > Sent: Monday, July 17, 2023 8:05 AM
> > To: linux-pci@...r.kernel.org; Bjorn Helgaas <bhelgaas@...gle.com>; Lorenzo
> > Pieralisi <lorenzo.pieralisi@....com>; Rob Herring <robh@...nel.org>;
> > Krzysztof Wilczyński <kw@...ux.com>; Emmanuel Grumbach
> > <emmanuel.grumbach@...el.com>; Rafael J . Wysocki <rafael@...nel.org>;
> > Heiner Kallweit <hkallweit1@...il.com>; Lukas Wunner <lukas@...ner.de>;
> > Andy Shevchenko <andriy.shevchenko@...ux.intel.com>; Deucher, Alexander
> > <Alexander.Deucher@....com>; Koenig, Christian
> > <Christian.Koenig@....com>; Pan, Xinhui <Xinhui.Pan@....com>; David
> > Airlie <airlied@...il.com>; Daniel Vetter <daniel@...ll.ch>; amd-
> > gfx@...ts.freedesktop.org; dri-devel@...ts.freedesktop.org; linux-
> > kernel@...r.kernel.org
> > Cc: Dean Luick <dean.luick@...nelisnetworks.com>; Jonas Dreßler
> > <verdre@...d.nl>; Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>;
> > stable@...r.kernel.org
> > Subject: [PATCH v5 06/11] drm/radeon: Use RMW accessors for changing
> > LNKCTL
> >
> > Don't assume that only the driver would be accessing LNKCTL. ASPM policy
> > changes can trigger write to LNKCTL outside of driver's control.
> > And in the case of upstream bridge, the driver does not even own the device
> > it's changing the registers for.
> >
> > Use RMW capability accessors which do proper locking to avoid losing
> > concurrent updates to the register value.
> >
> > Fixes: 8a7cd27679d0 ("drm/radeon/cik: add support for pcie gen1/2/3
> > switching")
> > Fixes: b9d305dfb66c ("drm/radeon: implement pcie gen2/3 support for SI")
> > Suggested-by: Lukas Wunner <lukas@...ner.de>
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > Cc: stable@...r.kernel.org
> 
> For this and the amdgpu patch:
> Acked-by: Alex Deucher <alexander.deucher@....com>
> I'm not sure if this is stable material however.  Is there some issue today?

Added your ack, thanks!  I dropped the stable tag on the whole series.

Bjorn