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Date:   Thu, 7 May 2020 16:10:15 -0500
From:   Rob Herring <robh@kernel.org>
To:     Pali =?iso-8859-1?Q?Roh=E1r?= <pali@kernel.org>
Cc:     Jason Cooper <jason@lakedaemon.net>, Andrew Lunn <andrew@lunn.ch>,
        Gregory Clement <gregory.clement@bootlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Andrew Murray <amurray@thegoodpenguin.co.uk>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Remi Pommarel <repk@triplefau.lt>,
        Marek =?iso-8859-1?Q?Beh=FAn?= <marek.behun@nic.cz>,
        Tomasz Maciej Nowak <tmn505@gmail.com>,
        Xogium <contact@xogium.me>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v4 04/12] PCI: aardvark: Improve link training
Message-ID: <20200507211015.GA31477@bogus>
References: <20200430080625.26070-1-pali@kernel.org>
 <20200430080625.26070-5-pali@kernel.org>
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On Thu, 30 Apr 2020 10:06:17 +0200, =?UTF-8?q?Pali=20Roh=C3=A1r?= wrote:
> From: Marek Beh?n <marek.behun@nic.cz>
> 
> Currently the aardvark driver trains link in PCIe gen2 mode. This may
> cause some buggy gen1 cards (such as Compex WLE900VX) to be unstable or
> even not detected. Moreover when ASPM code tries to retrain link second
> time, these cards may stop responding and link goes down. If gen1 is
> used this does not happen.
> 
> Unconditionally forcing gen1 is not a good solution since it may have
> performance impact on gen2 cards.
> 
> To overcome this, read 'max-link-speed' property (as defined in PCI
> device tree bindings) and use this as max gen mode. Then iteratively try
> link training at this mode or lower until successful. After successful
> link training choose final controller gen based on Negotiated Link Speed
> from Link Status register, which should match card speed.
> 
> Signed-off-by: Pali Roh?r <pali@kernel.org>
> Signed-off-by: Marek Beh?n <marek.behun@nic.cz>
> ---
>  drivers/pci/controller/pci-aardvark.c | 114 ++++++++++++++++++++------
>  1 file changed, 89 insertions(+), 25 deletions(-)
> 

Reviewed-by: Rob Herring <robh@kernel.org>