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Received: from shell.armlinux.org.uk ([2002:4e20:1eda:1:5054:ff:fe00:4ec]:56526) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1j9qwh-0006mH-7U; Thu, 05 Mar 2020 13:53:51 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1j9qwc-0007y5-JN; Thu, 05 Mar 2020 13:53:46 +0000 Date: Thu, 5 Mar 2020 13:53:46 +0000 From: Russell King - ARM Linux admin To: Philippe Schenker Subject: Re: [PATCH] ARM: mach-imx6q: add ksz9131rn_phy_fixup Message-ID: <20200305135346.GD25745@shell.armlinux.org.uk> References: <20200305134928.19775-1-philippe.schenker@toradex.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200305134928.19775-1-philippe.schenker@toradex.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200305_055606_705294_2BD61D1F X-CRM114-Status: GOOD ( 23.30 ) 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: , Cc: linux-arm-kernel@lists.infradead.org, Kate Stewart , Greg Kroah-Hartman , Sascha Hauer , linux-kernel@vger.kernel.org, NXP Linux Team , Pengutronix Kernel Team , Shawn Guo , Thomas Gleixner , Fabio Estevam , Allison Randal 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 On Thu, Mar 05, 2020 at 02:49:28PM +0100, Philippe Schenker wrote: > The MAC of the i.MX6 SoC is compliant with RGMII v1.3. The KSZ9131 PHY > is like KSZ9031 adhering to RGMII v2.0 specification. This means the > MAC should provide a delay to the TXC line. Because the i.MX6 MAC does > not provide this delay this has to be done in the PHY. > > This patch adds by default ~1.6ns delay to the TXC line. This should > be good for all boards that have the RGMII signals routed with the > same length. > > The KSZ9131 has relatively high tolerances on skew registers from > MMD 2.4 to MMD 2.8. Therefore the new DLL-based delay of 2ns is used > and then as little as possibly subtracted from that so we get more > accurate delay. This is actually needed because the i.MX6 SoC has > an asynchron skew on TXC from -100ps to 900ps, to get all RGMII > values within spec. > > Signed-off-by: Philippe Schenker > > --- > > arch/arm/mach-imx/mach-imx6q.c | 37 ++++++++++++++++++++++++++++++++++ > 1 file changed, 37 insertions(+) > > diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c > index edd26e0ffeec..8ae5f2fa33e2 100644 > --- a/arch/arm/mach-imx/mach-imx6q.c > +++ b/arch/arm/mach-imx/mach-imx6q.c > @@ -61,6 +61,14 @@ static void mmd_write_reg(struct phy_device *dev, int device, int reg, int val) > phy_write(dev, 0x0e, val); > } > > +static int mmd_read_reg(struct phy_device *dev, int device, int reg) > +{ > + phy_write(dev, 0x0d, device); > + phy_write(dev, 0x0e, reg); > + phy_write(dev, 0x0d, (1 << 14) | device); > + return phy_read(dev, 0x0e); > +} These look like the standard MII MMD registers, and it also looks like you're reinventing phy_read_mmd() - but badly due to lack of locking. I guess you need this because phy_read_mmd() may be modular - maybe we should arrange for the accessors to be separately buildable into the kernel, so that such fixups can stop badly reinventing the wheel? > + > static int ksz9031rn_phy_fixup(struct phy_device *dev) > { > /* > @@ -74,6 +82,33 @@ static int ksz9031rn_phy_fixup(struct phy_device *dev) > return 0; > } > > +#define KSZ9131_RXTXDLL_BYPASS 12 > + > +static int ksz9131rn_phy_fixup(struct phy_device *dev) > +{ > + int tmp; > + > + tmp = mmd_read_reg(dev, 2, 0x4c); > + /* disable rxdll bypass (enable 2ns skew delay on RXC) */ > + tmp &= ~(1 << KSZ9131_RXTXDLL_BYPASS); > + mmd_write_reg(dev, 2, 0x4c, tmp); > + > + tmp = mmd_read_reg(dev, 2, 0x4d); > + /* disable txdll bypass (enable 2ns skew delay on TXC) */ > + tmp &= ~(1 << KSZ9131_RXTXDLL_BYPASS); > + mmd_write_reg(dev, 2, 0x4d, tmp); > + > + /* > + * Subtract ~0.6ns from txdll = ~1.4ns delay. > + * leave RXC path untouched > + */ > + mmd_write_reg(dev, 2, 4, 0x007d); > + mmd_write_reg(dev, 2, 6, 0xdddd); > + mmd_write_reg(dev, 2, 8, 0x0007); > + > + return 0; > +} > + > /* > * fixup for PLX PEX8909 bridge to configure GPIO1-7 as output High > * as they are used for slots1-7 PERST# > @@ -167,6 +202,8 @@ static void __init imx6q_enet_phy_init(void) > ksz9021rn_phy_fixup); > phy_register_fixup_for_uid(PHY_ID_KSZ9031, MICREL_PHY_ID_MASK, > ksz9031rn_phy_fixup); > + phy_register_fixup_for_uid(PHY_ID_KSZ9131, MICREL_PHY_ID_MASK, > + ksz9131rn_phy_fixup); > phy_register_fixup_for_uid(PHY_ID_AR8031, 0xffffffef, > ar8031_phy_fixup); > phy_register_fixup_for_uid(PHY_ID_AR8035, 0xffffffef, > -- > 2.25.1 > > -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel