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Thu, 14 Feb 2019 19:15:04 -0500 Received: by mail-pg1-f196.google.com with SMTP id d72so3899452pga.9; Thu, 14 Feb 2019 16:15:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:openpgp:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=DfwpAIBPbdY0QYCNZoLHI6jDCroYDw3GB2IJ2+SDNMo=; b=sL9lozulcKoZI24rDC+KL1T1Yi5CEjXtNvTPCL+5qvTFSczQ7Liy5bp+RHiDgT4cAa mmFJfqFrneGHv9VoYi/1W7GAnuGIpKLusx5as6OqbRLJayYh3IbVw6hmSIqqgm94WJyr NJuHzy4TrIaNF97CLAdFhLnTGdK/gtjX8/hpz35qacJjUNzXHwdzLVclh16tQTf7BImy 6zkP1EANstGXVokioRsMmZDputMpvRqWB/SNI5TYgLRqHNqKz7gcZ4QcZjwyauVeSzLi 4NTz/jRuQh5B4n7rJpArz4PbSlhIZtCYWEh8/5mtrpDjqpp7IHPlkY6knj3GBNqpxvzL 58vg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=DfwpAIBPbdY0QYCNZoLHI6jDCroYDw3GB2IJ2+SDNMo=; b=jhp6i8C2yb+YoN81VPowqwGYJcMwTZC7hinFtAfzqQoRTB3f8X8XuDTBLuI3gV6a71 Tl+MJfODdUbI/quZl/+mJCoWkFVSv0dP6bi47HA2Hcu4JsnbdhzL8MlEHzVBARjEUmHv iHzN3ukYt7ezVa0vDSDtkttTij0PRkFL8nrTMNpLaGYfMTj2JbEplD85jcZPEBrhl591 3q2mag8d4BrgBL1vi/0UcQnO/lYo5NKppR0bfqTyzB9lcTQOOG++DeOUz/tBL3LEYskR Ai7Bm1ZVs/PAy05fQBVQC4N0h1/BWTfi+He6lWHXKnSbNbdVsnpGT+zr5q+Vyl2/0SYS JFrg== X-Gm-Message-State: AHQUAubXHV+gvOcI/M+8LBcbQe3SDq4eCxuf0MLCBFS5ww0lPZWWK2Ul Npt6CgxdSh3VRme+CI0mlsA= X-Google-Smtp-Source: AHgI3IZETDpw3JXRr53fh+TvIvBzgKi/n901T2WH0Mfr6sLbCgTzBNhw4XGagwCYlJZwrvFUddF7Rg== X-Received: by 2002:a63:d703:: with SMTP id d3mr2606183pgg.167.1550189703444; Thu, 14 Feb 2019 16:15:03 -0800 (PST) Received: from [10.67.48.220] ([192.19.223.250]) by smtp.googlemail.com with ESMTPSA id m68sm10264418pfj.89.2019.02.14.16.14.59 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Feb 2019 16:15:02 -0800 (PST) Subject: Re: [PATCH] net: phy: at803x: disable delay only for RGMII mode To: Niklas Cassel , Peter Ujfalusi Cc: Marc Gonzalez , Andrew Lunn , Vinod Koul , David S Miller , linux-arm-msm@vger.kernel.org, Bjorn Andersson , netdev@vger.kernel.org, "Nori, Sekhar" References: <20190212141922.12849-1-vkoul@kernel.org> <20190213131206.GA460@centauri.lan> <20190213132900.GA24589@lunn.ch> <1ab5edac-a36c-9dc5-52e5-dbd3b70e7728@free.fr> <20190213174034.GA6954@centauri.lan> <3356ff05-8d08-591e-03bf-9d846f79097b@ti.com> <20190214123922.GA28897@centauri.ideon.se> <96271de7-bda1-a86a-a78e-e132bc097efb@ti.com> <20190214150649.GA29957@centauri.lan> From: Florian Fainelli Openpgp: preference=signencrypt Autocrypt: addr=f.fainelli@gmail.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190214150649.GA29957@centauri.lan> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2/14/19 7:06 AM, Niklas Cassel wrote: > On Thu, Feb 14, 2019 at 03:22:28PM +0200, Peter Ujfalusi wrote: >> Hi Niklas, >> >> On 14/02/2019 14.39, Niklas Cassel wrote: >>>>> So, I've rebased your old patch, see attachment. >>>>> I suggest that Peter test it on am335x-evm. >>>> >>>> with the patch + s/rgmii-txid/rgmii-id in the am335x-evmsk.dts ethernet >>>> is working. >>>> I don't have am335x-evm to test, but it has the same PHY as evmsk. >>>> >>> >>> Florian's concern was that this PHY driver looked at "phy-mode" from the >>> perspective of the MAC rather than the PHY. >>> However, if s/rgmii-txid/rgmii-id is the correct fix for am335x-evm, >>> then this means that this PHY driver was just broken. >>> >>> If the driver had misinterpreted the perspective, then the correct >>> fix for am335x-evm would have been s/rgmii-txid/rgmii-rxid. >> >> Not sure if I got this right, but: >> rgmii-id/txid/rxid is the delay mode between PHY and MAC, right? >> on the PHY node it is from the PHY perspective, right? > > Yes, from the PHY perspective. > > (According to Florian, IIUC, some old PHY drivers were implemented before > it was decided that it is from PHY perspective, rather than from MAC > perspective.) > >> >> The errata I have mentioned for am335x say: >> "The reset state of RGMII1_IDMODE (bit 4) and RGMII2_IDMODE (bit 5) in >> the GMII_SEL register enables internal delay mode on the transmit clock >> of the respective RGMII port. The AM335x device does not support >> internal delay mode, so RGMII1_IDMODE and RGMII2_IDMODE must be set to 1b." >> >> If the delay mode on the transmit clock is not working on the am335x, >> then this translate that the rxid needs to be enabled on the PHY side? > > IIUC what Florian explained, then either MAC or PHY needs to add delays, > so if the PHY only adds delay on e.g. TX, then the MAC needs to add delay > on RX. > > However, in your case, the errata says that your MAC is not capable of > adding a delay on TX, therefore the PHY needs to add a delay on TX. So that mandates specifying either 'rgmii-id' or 'rgmii-txid'. > >> >> But then why it worked when only the txid was enabled and rxid was not >> on the PHY side, and why it works if both txid and rxid is enabled? > > Because the PHY driver was broken, so the PHY driver always enabled > delays on both TX and RX. > > This is how the driver looked before Vinod's change: > > if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID || > phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) { > ret = at803x_enable_rx_delay(phydev); > if (ret < 0) > return ret; > } > > if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID || > phydev->interface == PHY_INTERFACE_MODE_RGMII_ID) { > ret = at803x_enable_tx_delay(phydev); > if (ret < 0) > return ret; > } > > > Yet, the initial value for this PHY is that both TX and RX delay is > enabled, and since this driver never disabled TX/RX delays, > the TX and RX delays were always enabled, no matter what phy-mode > you specified. Fixing all PHY drivers is probably too much, but since we seem to have traction and people assigned to QCOM working on this at803x PHY driver, then let's fix it correctly, I agree with that. So that means: - disable both RX and TX delay by default - if RGMII_RXID or RGMII_ID is specified: turn on RX delay - if RGMII_TXID or RGMII_ID is specified: turn on TX delay so basically the patch above, with an initial delay disabling for both RX and TX. Then we fix all DTSes to be correct, at least those in tree and we provide appropriate Fixes: tag so things get backported automatically. How does that sound? -- Florian