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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uW9v1-00000001cU3-0MTo; Mon, 30 Jun 2025 08:31:15 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uW9pr-00000001bs3-316S for linux-arm-kernel@lists.infradead.org; Mon, 30 Jun 2025 08:25:57 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id E371EA530C7; Mon, 30 Jun 2025 08:25:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CA29C4CEE3; Mon, 30 Jun 2025 08:25:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751271954; bh=z0myKlXPfbFRymUmSLOvc/7wdeydzOpDX+kckyTt+DU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=H6DWQF+TK/2PdqRJ0ssZolMe6dG9ZvpfffQngfJfx8Gf1b62TytLTPAzXSyYRVAFV 4jGSfJ158J/K35wRR3J2J//j0zU8G7H0zxVPMA2iZ6qk/++nm6hHhEh7LsaWLg3To4 Di9y5uLOdsQ3JEfP2M9bFSc4yBUjmKvWhvX1oKg+S/iQtU1lS/Y9eEEi2Y/3Lky9/w KfiFIPry17J35amVx4bj/G2ym5EGLN5eRH+5/2Sq2DtW7pqkjpPRm7Vnu0UeHUXTwj CyX0Yr8tCzvjRPEDaL8NJaCm5io3d1PIGNE14Gl2C+tspLHvglRlS6PW9Ho1mOGooz 5ZHp6OzQnzaJg== Message-ID: <98b00dd1-3b83-4beb-ad06-f3e0442df8c7@kernel.org> Date: Mon, 30 Jun 2025 10:25:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/3] dt-bindings: PCI: dwc: Add one more reference clock To: Frank Li Cc: Richard Zhu , l.stach@pengutronix.de, lpieralisi@kernel.org, kwilczynski@kernel.org, mani@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, bhelgaas@google.com, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org References: <20250626073804.3113757-1-hongxing.zhu@nxp.com> <20250626073804.3113757-2-hongxing.zhu@nxp.com> <20250627-sensible-pigeon-of-reading-b021a3@krzk-bin> <20250628-vigorous-benevolent-crayfish-bcbae5@krzk-bin> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250630_012555_910014_A91D939F X-CRM114-Status: GOOD ( 22.58 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 28/06/2025 17:33, Frank Li wrote: > On Sat, Jun 28, 2025 at 02:34:12PM +0200, Krzysztof Kozlowski wrote: >> On Fri, Jun 27, 2025 at 04:09:49PM -0400, Frank Li wrote: >>> On Fri, Jun 27, 2025 at 08:54:46AM +0200, Krzysztof Kozlowski wrote: >>>> On Thu, Jun 26, 2025 at 03:38:02PM +0800, Richard Zhu wrote: >>>>> Add one more reference clock "extref" to be onhalf the reference clock >>>>> that comes from external crystal oscillator. >>>>> >>>>> Signed-off-by: Richard Zhu >>>>> --- >>>>> .../devicetree/bindings/pci/snps,dw-pcie-common.yaml | 6 ++++++ >>>>> 1 file changed, 6 insertions(+) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml b/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml >>>>> index 34594972d8db..ee09e0d3bbab 100644 >>>>> --- a/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml >>>>> +++ b/Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml >>>>> @@ -105,6 +105,12 @@ properties: >>>>> define it with this name (for instance pipe, core and aux can >>>>> be connected to a single source of the periodic signal). >>>>> const: ref >>>>> + - description: >>>>> + Some dwc wrappers (like i.MX95 PCIes) have two reference clock >>>>> + inputs, one from internal PLL, the other from off chip crystal >>>>> + oscillator. Use extref clock name to be onhalf of the reference >>>>> + clock comes form external crystal oscillator. >>>> >>>> How internal PLL can be represented as 'ref' clock? Internal means it is >>>> not outside, so impossible to represent. >>> >>> Internal means in side SoC, but outside PCIe controller. >> >> So external... It does not matter for PCIe controller whether clock is >> coming from SoC or from some crystal. It is still input pin. Same input >> pin. > > It is NOT the same pin. It is TWO pins, there are mux inside in PCI > controller. > > There are similar cases in s32 rtc, there are 4 input source[0,1,2,3] > https://lore.kernel.org/imx/20241127144322.GA3454134-robh@kernel.org/ > Only one provide. > >> >>> >>>> >>>> Where is the DTS so we can look at big picture? >>> >>> imx94 pci's upstream is still on going, which quite similar with imx95. >>> Just board design choose external crystal. >>> >>> pcie_ref_clk: clock-pcie-ref { >>> compatible = "gpio-gate-clock"; >>> clocks = <&xtal25m>; >>> #clock-cells = <0>; >>> enable-gpios = <&pca9670_i2c3 7 GPIO_ACTIVE_LOW>; >>> }; >>> >>> &pcie0 { >>> pinctrl-0 = <&pinctrl_pcie0>; >>> pinctrl-names = "default"; >>> clocks = <&scmi_clk IMX94_CLK_HSIO>, >>> <&scmi_clk IMX94_CLK_HSIOPLL>, >>> <&scmi_clk IMX94_CLK_HSIOPLL_VCO>, >>> <&scmi_clk IMX94_CLK_HSIOPCIEAUX>, >>> <&pcie_ref_clk>; >>> clock-names = "pcie", "pcie_bus", "pcie_phy", "pcie_aux", "ext-ref"; >> >> So this is totally faked hardware property. >> >> No, it is the same clock signal, not different. You write bindings from >> this device point of view, not for your board. > > No the same clock signal. There are two sources, "ext-ref" or "ref". > PCI controller need know which one provide clocks. OK, this should be clearly expressed not some vague play of the words what is internal and external... > > There are mux inside PCI controller, DT need provide information which on > provide. > > Maybe my example dts miss-lead you. Altherate descript is > clock-names = "pcie", "pcie_bus", "pcie_phy", "pcie_aux", "ref", "ext-ref"; > > But we thinks if ext-ref provide, "ref" is not neccesary need be turn on. > So remove it from the list. If the ref clock is actually wired it should be there. You describe here hardware, not what is necessary. Best regards, Krzysztof