From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 540DAC4332B for ; Thu, 19 Mar 2020 16:17:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 293722072C for ; Thu, 19 Mar 2020 16:17:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728267AbgCSQRV convert rfc822-to-8bit (ORCPT ); Thu, 19 Mar 2020 12:17:21 -0400 Received: from relay8-d.mail.gandi.net ([217.70.183.201]:43675 "EHLO relay8-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727700AbgCSQRU (ORCPT ); Thu, 19 Mar 2020 12:17:20 -0400 X-Originating-IP: 90.76.143.236 Received: from localhost (lfbn-tou-1-1075-236.w90-76.abo.wanadoo.fr [90.76.143.236]) (Authenticated sender: antoine.tenart@bootlin.com) by relay8-d.mail.gandi.net (Postfix) with ESMTPSA id 0E4F81BF20C; Thu, 19 Mar 2020 16:17:18 +0000 (UTC) Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT In-Reply-To: <20200319160505.GE27807@lunn.ch> References: <20200319141958.383626-1-antoine.tenart@bootlin.com> <20200319141958.383626-3-antoine.tenart@bootlin.com> <20200319160505.GE27807@lunn.ch> Cc: davem@davemloft.net, f.fainelli@gmail.com, hkallweit1@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org From: Antoine Tenart Subject: Re: [PATCH net-next v3 2/2] net: phy: mscc: RGMII skew delay configuration To: Andrew Lunn Message-ID: <158463463741.3149.13095217659080007040@kwain> Date: Thu, 19 Mar 2020 17:17:17 +0100 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrew, Quoting Andrew Lunn (2020-03-19 17:05:05) > On Thu, Mar 19, 2020 at 03:19:58PM +0100, Antoine Tenart wrote: > > This patch adds support for configuring the RGMII skew delays in Rx and > > Tx. The Rx and Tx skews are set based on the interface mode. By default > > their configuration is set to the default value in hardware (0.2ns); > > this means the driver do not rely anymore on the bootloader > > configuration. > > > > Then based on the interface mode being used, a 2ns delay is added: > > - RGMII_ID adds it for both Rx and Tx. > > - RGMII_RXID adds it for Rx. > > - RGMII_TXID adds it for Tx. > > > > Signed-off-by: Antoine Tenart > > --- > > drivers/net/phy/mscc/mscc.h | 14 ++++++++++++++ > > drivers/net/phy/mscc/mscc_main.c | 29 +++++++++++++++++++++++++++++ > > 2 files changed, 43 insertions(+) > > > > diff --git a/drivers/net/phy/mscc/mscc.h b/drivers/net/phy/mscc/mscc.h > > index d1b8bbe8acca..25729302714c 100644 > > --- a/drivers/net/phy/mscc/mscc.h > > +++ b/drivers/net/phy/mscc/mscc.h > > @@ -161,6 +161,20 @@ enum rgmii_rx_clock_delay { > > /* Extended Page 2 Registers */ > > #define MSCC_PHY_CU_PMD_TX_CNTL 16 > > > > +#define MSCC_PHY_RGMII_SETTINGS 18 > > +#define RGMII_SKEW_RX_POS 1 > > +#define RGMII_SKEW_TX_POS 4 > > + > > +/* RGMII skew values, in ns */ > > +#define VSC8584_RGMII_SKEW_0_2 0 > > +#define VSC8584_RGMII_SKEW_0_8 1 > > +#define VSC8584_RGMII_SKEW_1_1 2 > > +#define VSC8584_RGMII_SKEW_1_7 3 > > +#define VSC8584_RGMII_SKEW_2_0 4 > > +#define VSC8584_RGMII_SKEW_2_3 5 > > +#define VSC8584_RGMII_SKEW_2_6 6 > > +#define VSC8584_RGMII_SKEW_3_4 7 > > > > +static void vsc8584_rgmii_set_skews(struct phy_device *phydev) > > +{ > > + u32 skew_rx, skew_tx; > > + > > + /* We first set the Rx and Tx skews to their default value in h/w > > + * (0.2 ns). > > + */ > > + skew_rx = VSC8584_RGMII_SKEW_0_2; > > + skew_tx = VSC8584_RGMII_SKEW_0_2; > > Does this mean it is impossible to have a skew of 0ns? It seems to be the case, the lowest value this register accepts is 0, which means a 0.2ns delay, according to the datasheet. And I'm not seeing any register disabling this when RGMII is used. Thanks! Antoine -- Antoine Ténart, Bootlin Embedded Linux and Kernel engineering https://bootlin.com