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[24.155.109.49]) by smtp.gmail.com with ESMTPSA id 4sm1770225oog.3.2020.05.07.14.07.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 May 2020 14:07:14 -0700 (PDT) Received: (nullmailer pid 26846 invoked by uid 1000); Thu, 07 May 2020 21:07:13 -0000 Date: Thu, 7 May 2020 16:07:13 -0500 From: Rob Herring To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Jason Cooper , Andrew Lunn , Gregory Clement , Sebastian Hesselbarth , Thomas Petazzoni , Lorenzo Pieralisi , Andrew Murray , Bjorn Helgaas , Remi Pommarel , Marek =?iso-8859-1?Q?Beh=FAn?= , Tomasz Maciej Nowak , Xogium , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH v4 02/12] PCI: aardvark: Don't blindly enable ASPM L0s and don't write to read-only register Message-ID: <20200507210713.GA26756@bogus> References: <20200430080625.26070-1-pali@kernel.org> <20200430080625.26070-3-pali@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200430080625.26070-3-pali@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, 30 Apr 2020 10:06:15 +0200, =?UTF-8?q?Pali=20Roh=C3=A1r?= wrote: > Trying to change Link Status register does not have any effect as this > is a read-only register. Trying to overwrite bits for Negotiated Link > Width does not make sense. > > In future proper change of link width can be done via Lane Count Select > bits in PCIe Control 0 register. > > Trying to unconditionally enable ASPM L0s via ASPM Control bits in Link > Control register is wrong. There should be at least some detection if > endpoint supports L0s as isn't mandatory. > > Moreover ASPM Control bits in Link Control register are controlled by > pcie/aspm.c code which sets it according to system ASPM settings, > immediately after aardvark driver probes. So setting these bits by > aardvark driver has no long running effect. > > Remove code which touches ASPM L0s bits from this driver and let > kernel's ASPM implementation to set ASPM state properly. > > Some users are reporting issues that this code is problematic for some > Intel wifi cards and removing it fixes them, see e.g.: > https://bugzilla.kernel.org/show_bug.cgi?id=196339 > > If problems with Intel wifi cards occur even after this commit, then > pcie/aspm.c code could be modified / hooked to not enable ASPM L0s state > for affected problematic cards. > > Signed-off-by: Pali Rohár > --- > drivers/pci/controller/pci-aardvark.c | 4 ---- > 1 file changed, 4 deletions(-) > Acked-by: Rob Herring