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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24152C433EF for ; Mon, 27 Sep 2021 17:18:02 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E787B61528 for ; Mon, 27 Sep 2021 17:18:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E787B61528 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:References: List-Owner; bh=m/NXpG/mF6nTsigtajPwcvI2+h/hutUx0betPuNfUoI=; b=dAt0ZlO8CLhLHP yQL511cMo3x+rO7FunzYgwQu6wP/6wo855t551nbkE/2ojftDUf7V6XZRWrdXGhNqZmQYji9q3wQX 8fhXJ/Js1MI7KjZM1j5JERm6N9IWmnRV5V8EJ0+xRKooz2iHOtsIFfqcGJSFCnNW5ueKDQm9BbHcZ H62eqN3YAPiwlq6titl7YHkzVMsrixFnWk30BTzEgUahu4kdoV/WVGVAfhCePU4mxB3Huy/S7D7jf 1NhtB1YmzdmIthRmxFKflGMBg5z/QlTefQ+i2uH69hiix04hpc+PIECp9HzroCLPTHFbzw3lC4uLp NSKadyUGlleL7HXqwvRQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mUuF6-003Xg7-Kt; Mon, 27 Sep 2021 17:16:40 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mUuF2-003Xfb-Ie for linux-arm-kernel@lists.infradead.org; Mon, 27 Sep 2021 17:16:38 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 82FB160E08; Mon, 27 Sep 2021 17:16:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632762995; bh=fiFXcjAyr/xbXvMc5MGt+1jLB423H4t84TnDpKWaMik=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=P5L1ZpilVa8FWpVdXv+LcxwmF4pAThXyw9LbPnxzSqk34x5HsQKMngUyiQ6TV/WDw 0oL3V+UbXcrKOqk+62vEypWryPX4oSQHXNp/Vd2rgq+YbZTMXTZS8Se9KY2uE/OXEW ACAcBD1Bc5J8lA/55oY/22TRuUTw13vfwd9ZjSw/w/7FsFxWyr26X8kQvwBtqugDZw up79h8bkFPqU234Zjsg9ccWWJ3QlXSJk42E7LErMoQgT39J3jDtB+gxCV5xHMHkUdR Z4/BtEkEVeHXSthBOyKwSYPSxa3SYrh210IZlDnvuw/BjJWSlJKKPeMkJLKjGCI8oW Kc5CurkAwpOdg== Date: Mon, 27 Sep 2021 12:16:34 -0500 From: Bjorn Helgaas To: Matthias Schiffer Cc: Richard Zhu , Lucas Stach , Shawn Guo , Sascha Hauer , Lorenzo Pieralisi , Rob Herring , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Bjorn Helgaas , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Markus Niebel Subject: Re: [RFC] PCI: imx6: add support for internal oscillator on i.MX7D Message-ID: <20210927171634.GA658570@bhelgaas> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <81c77a29362433fc5629ada442f0489046ce1051.1632319151.git.matthias.schiffer@ew.tq-group.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210927_101636_674787_05C97775 X-CRM114-Status: GOOD ( 40.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 24, 2021 at 10:05:15AM +0200, Matthias Schiffer wrote: > Adds support for a DT property fsl,internal-osc to select the internal > oscillator for the PCIe PHY. If you repost this, please update the subject to match the conventions (use "git log --oneline drivers/pci/controller/dwc/pci-imx6.c" and note capitalization). > Signed-off-by: Matthias Schiffer > Cc: Markus Niebel > --- > > Okay, so while this patch is nice and short, I'm note sure if it's a good > solution, hence I submit it as an RFC. It is roughly based on code from > older linux-imx versions [1] - although it seems this feature was never > supported on i.MX7D even by linux-imx (possibly because of compliance > issues with the internal clock, however I haven't found a definitive > erratum backing this), but only on other SoC like i.MX6QP. > > The device tree binding docs of the driver are somewhat lacking, but > looking at [1] it seems that an external reference clock takes the place of > the "pcie_bus" clock - various pieces of the driver skip enabling/disabling > this clock when an external clock is configured. > > From this I've come to the conclusion that the clock settings in > imx7d.dtsi do not really make sense: The pcie_bus clock is configured to > PLL_ENET_MAIN_100M_CLK, but this seems wrong for both internal and > external reference clocks: > > - For the internal clock, the correct clock should be PCIE_PHY_ROOT_CLK > according to the reference manual > - The external clocks, this should refer to an actual external clock, or > possibly a fixed-clock node > > I would be great if someone with more insight into this could chime in > and tell me if my reasoning here is correct or not. > > Unfortunately I only have our MBa7x at my disposal for further > experimentation. This board does not have an external reference clock for > the PCIe PHY, so I cannot test the behaviour for settings that use an > external clock. Without this patch (and adding the new flag to the MBa7x > DTS), the boot will hang while waiting for the PCIe link to come up. > > So, for the actual question (given that my thoughts above make any sense): > How do we want to implement this? > > 1. A simple boolean flag, like this patch provides > 2. Allow Device Trees not to specify a "pcie_bus" clock at all, meaning > it should use the internal clock > 3. Special handling when the "pcie_bus" clock is configured to > PCIE_PHY_ROOT_CLK - is such a thing even possible, or is this > breaking the clock driver's abstraction too much? > 4. Something more involved, with a proper clock sel as the source for > "pcie_bus" > > Solution 4. seems difficult to implement nicely, as the PCIe driver > also fiddles with IMX7D_GPR12_PCIE_PHY_REFCLK_SEL for power management: > the clock selection is switched back to the internal clock in > imx6_pcie_clk_disable(), which also disables its source PCIE_PHY_ROOT_CLK, > effectively gating the clock. > > Regards, > Matthias > > > [1] https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/pci/host/pci-imx6.c?h=imx_4.1.15_2.0.0_ga > > drivers/pci/controller/dwc/pci-imx6.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c > index 80fc98acf097..021499b9ee7c 100644 > --- a/drivers/pci/controller/dwc/pci-imx6.c > +++ b/drivers/pci/controller/dwc/pci-imx6.c > @@ -83,6 +83,7 @@ struct imx6_pcie { > struct regulator *vpcie; > struct regulator *vph; > void __iomem *phy_base; > + bool internal_osc; Prefer bitfield ("unsigned int internal_osc:1") over bool in structs. > /* power domain for pcie */ > struct device *pd_pcie; > @@ -637,7 +638,9 @@ static void imx6_pcie_init_phy(struct imx6_pcie *imx6_pcie) > break; > case IMX7D: > regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12, > - IMX7D_GPR12_PCIE_PHY_REFCLK_SEL, 0); > + IMX7D_GPR12_PCIE_PHY_REFCLK_SEL, > + imx6_pcie->internal_osc ? > + IMX7D_GPR12_PCIE_PHY_REFCLK_SEL : 0); > break; > case IMX6SX: > regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12, > @@ -1130,6 +1133,9 @@ static int imx6_pcie_probe(struct platform_device *pdev) > &imx6_pcie->tx_swing_low)) > imx6_pcie->tx_swing_low = 127; > > + if (of_property_read_bool(node, "fsl,internal-osc")) > + imx6_pcie->internal_osc = true; > + > /* Limit link speed */ > pci->link_gen = 1; > ret = of_property_read_u32(node, "fsl,max-link-speed", &pci->link_gen); > -- > 2.17.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel