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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hnjvv-0007K2-MT; Wed, 17 Jul 2019 13:25:23 +0000 Received: from perceval.ideasonboard.com ([2001:4b98:dc2:55:216:3eff:fef7:d647]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hnjvr-00074i-0G for linux-arm-kernel@lists.infradead.org; Wed, 17 Jul 2019 13:25:21 +0000 Received: from [192.168.0.20] (cpc89242-aztw30-2-0-cust488.18-1.cable.virginm.net [86.31.129.233]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id C955533C; Wed, 17 Jul 2019 15:24:54 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1563369895; bh=DdgjDJoPwjp9kpyXsHGQjTFqs6XaGIWGUgdg5XcEieQ=; h=Subject:To:Cc:References:Reply-To:From:Date:In-Reply-To:From; b=jAedL8l6jBq3cTHxzsgbAS2UNhXSAo+hwnvzoQ9W0uCjkXvlNZiSfVV09uHiR2XBS AWoq+xAPt9o0XQj8albr71kkevByHUjwJAV/+NY2WIYFHYfu0R6vcLaphRTELlt23p e+wuw/lUtSuYLRb2MUepLjfx0keJpY0HianbTSdA= Subject: Re: [PATCH/RFC repost] arm64: dts: renesas: ebisu, draak: Limit EtherAVB to 100Mbps To: Simon Horman , Geert Uytterhoeven , linux-renesas-soc@vger.kernel.org References: <20190717125739.21450-1-horms+renesas@verge.net.au> From: Kieran Bingham Organization: Ideas on Board Message-ID: Date: Wed, 17 Jul 2019 14:24:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190717125739.21450-1-horms+renesas@verge.net.au> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190717_062520_619139_CED99356 X-CRM114-Status: GOOD ( 19.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: kieran.bingham+renesas@ideasonboard.com Cc: Andrew Lunn , Magnus Damm , linux-arm-kernel@lists.infradead.org, Wolfram Sang Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Simon, On 17/07/2019 13:57, Simon Horman wrote: > * According to the R-Car Gen3 Hardware Manual Errata for Rev 1.00 of > August 24, 2018, the TX clock internal delay mode isn't supported > on R-Car E3 (r8a77990) and D3 (r8a77995). > > * TX clock internal delay mode is required for reliable 1Gbps communication > using the KSZ9031RNX phy present on the Ebisu and Draak boards. > > Thus, the E3 based Ebisu and D3 based Draak boards reliably use 1Gbps and > the speed should be limited to 100Mbps. I believe you might mean 'can not' reliable use 1Gbps here :-) Regards Kieran > > Based on work by Kazuya Mizuguchi. > > Signed-off-by: Simon Horman > > --- > > This is a repost of this change. > > In earlier review Andrew Lunn suggested that we may be able to take a > different approach to this problem by using delays provided by the > KSZ9031RNX PHY. In particular MMD address 2h, Register 8h - > RGMII Clock Pad Skew. > > I have consulted with Renesas regarding this suggestion, however, > unfortunately it appears that the delays provided by this solution > would be insufficient to allow for reliable 1Gbps communication. > > At this point I believe the safest option is to apply this patch. > --- > arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts | 1 + > arch/arm64/boot/dts/renesas/r8a77995-draak.dts | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts > index 83fc13ac3fa1..3d3d6d438a05 100644 > --- a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts > +++ b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts > @@ -271,6 +271,7 @@ > interrupt-parent = <&gpio2>; > interrupts = <21 IRQ_TYPE_LEVEL_LOW>; > reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>; > + max-speed = <100>; > }; > }; > > diff --git a/arch/arm64/boot/dts/renesas/r8a77995-draak.dts b/arch/arm64/boot/dts/renesas/r8a77995-draak.dts > index 0711170b26b1..eb153323ed13 100644 > --- a/arch/arm64/boot/dts/renesas/r8a77995-draak.dts > +++ b/arch/arm64/boot/dts/renesas/r8a77995-draak.dts > @@ -175,6 +175,7 @@ > reg = <0>; > interrupt-parent = <&gpio5>; > interrupts = <19 IRQ_TYPE_LEVEL_LOW>; > + max-speed = <100>; > }; > }; > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel