From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f180.google.com (mail-pl1-f180.google.com [209.85.214.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A4FE1DF26F for ; Sun, 19 Jan 2025 15:25:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737300345; cv=none; b=uy6y/rySZKI2aPFbcmLstPrUZSZSt8tHscXNQuahjEmfILw3MhpS7yF+70IxunDN+mH/OelTIvL1nPEYGpH1J25t7Ww4+ZoSQntYcAPQKSV6Hx32tOO0lfY/Nl1d5DgleJdSdG3wtoqBFGx5WY3Ka7s5xJwuVkE3rx58KcmrHCk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737300345; c=relaxed/simple; bh=Cy+qEt2NXA08rztWXxtWOUDQnA+zPs8tkSV/b/YP8cg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OJOO9OsLXdQSvGzTumrHBr5BqDfSPWvulLQnxG1LNOiVpqD0WavgaRGjXShW0faEsu/BCJ1M0FCF/dUOOTYkU8c6FF77JXgriGd0oFK41ZgYHsPgTu9ranzoQYkueiY2jFLrpx1coE/qZp0nCP6G55l3/WyHEyPmfxmEruEDFMg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=d4Pkol1d; arc=none smtp.client-ip=209.85.214.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="d4Pkol1d" Received: by mail-pl1-f180.google.com with SMTP id d9443c01a7336-2165448243fso82858385ad.1 for ; Sun, 19 Jan 2025 07:25:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1737300342; x=1737905142; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=/Xaz6uw75PCkZ9efkLrpzdDAN7b8HSpOlZoyxfAfNzA=; b=d4Pkol1dokuOH1MaNAvFMBMBooHtTRQ9Ysh3eHP43FUrR+2juI4Uk2/KRkKTV/Jkoa 02qE9NKcRqMGR0F8VMDIXCdW1u7CSwG2pCeDlHsl/sPvzCvYYSLTC5nsaitlpp3GGRhp HfwycpvJfp1jigJXKYAA+NtiC5jEW4eVtPn1hVtIKfRvemxqH4lqXPl7R8fKQOdzoUZ2 UBqdn0P2N4JwYL5mOVCXVBQbY6HdsIASDYtPy4mb/LchFBMnsPDR57xVAUkWJ1mC60BO q0/EDPwFg2NzoD4UEXFnlb+jBkpcHcjBH9ZIkrfMA4bDTuWWrzQPZyMQHmZZ13YJZPes nhsQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737300342; x=1737905142; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/Xaz6uw75PCkZ9efkLrpzdDAN7b8HSpOlZoyxfAfNzA=; b=Lf/iIvQJZ6nyEEr7W5dZU9NiciucceW9ecLfj8B8oe/dWVliqHs/zgesygj+dWoPKy sWEmgr+N1LHNqKrJWO03YGJEPNijpU6MXEwfD5YSGmq6ZyarPtEWBq8/fU3yTmIRBJ8v Lssg+d268SKO7lvEmnhL1KofoU7axV7BmlLTptcx78P5ZBPm8w8Q548oXcUi4amuU8Hv 0Ae+wZcPVc00yy6f5xIh/fmgWcyF0P+dVMz+iReYusHTn2kvFHdJk4jO+poDo4RwLqH/ w4HoEQbACQR8j77377xcuPvf8JZsHS8NMtOK0wjJay+T2GISkjWLDYLNWTrd8QRLsl0p IOCA== X-Forwarded-Encrypted: i=1; AJvYcCXlODr48oI4kg11ae6layVuroiX5zoTjM4/5TN0OAX6STloG6VkccFtdWFGmZm8/uU3fUGJwTvyMGZd/lJr@vger.kernel.org X-Gm-Message-State: AOJu0Yy8FA71AsANQGK4In9VHSxL4aafRG9xfhqp/uX6Mrb3dPlsPLN3 1o83wiei2BiKO3GVb+QrPE5dwFN5HHEd9h0+bKfKiFSz4Y0I4OqE4Qb4MyZinQ== X-Gm-Gg: ASbGncsHhQw9S5Nxr6P7fotK/z2wPvb9jLnv+9nmpULkWNvhdSskxS4/DyKdazodYoE M6glFPf1sDLY5AblpTJGZ4UEnmMPhXL21F4ne4vw4xGqmDYdjWAdw8f7H8wJAz2HkWTuJ67hC7i Z+ddHY572nstz+4iB/Ug9w2TmaXOze7s5qwAfA6GnQdb46bES01QmrH7js7bl7e/1VMrU2XRXkl MFsEM1jx+jnn1VV6zZU0h8wHd3uoEtVSMVt5nKA8GV9GgY9JxQm3e1uL/D+lmFWameVqIO51Lm1 Y4Rmlw== X-Google-Smtp-Source: AGHT+IFwl8xnvKB2lpUjrtIYdeNsW1GvDBlcIZmazybTfoK6NpRu6tzeYc5RWcWJiKkCBQ9HdBR63w== X-Received: by 2002:a05:6a20:2585:b0:1d8:a9c0:8853 with SMTP id adf61e73a8af0-1eb214b22c8mr14523957637.23.1737300341700; Sun, 19 Jan 2025 07:25:41 -0800 (PST) Received: from thinkpad ([120.56.195.253]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72dab9c8e37sm5275988b3a.119.2025.01.19.07.25.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 19 Jan 2025 07:25:41 -0800 (PST) Date: Sun, 19 Jan 2025 20:55:34 +0530 From: Manivannan Sadhasivam To: Bjorn Helgaas Cc: Rob Herring , Rob Herring , Bjorn Andersson , Konrad Dybcio , Krzysztof Kozlowski , Conor Dooley , cros-qcom-dts-watchers@chromium.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, =?utf-8?B?TsOtY29sYXMgRi4gUi4gQS4=?= Prado Subject: Re: [PATCH v2 01/21] arm64: dts: qcom: sm8250: Add PCIe bridge node Message-ID: <20250119152534.d6berucbb2wbbi3z@thinkpad> References: <20250115175918.2isv2at337cfgvjd@thinkpad> <20250115181340.GA539092@bhelgaas> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250115181340.GA539092@bhelgaas> On Wed, Jan 15, 2025 at 12:13:40PM -0600, Bjorn Helgaas wrote: > On Wed, Jan 15, 2025 at 11:29:18PM +0530, Manivannan Sadhasivam wrote: > > On Wed, Jan 15, 2025 at 11:42:10AM -0600, Bjorn Helgaas wrote: > > > On Wed, Jan 15, 2025 at 04:24:31PM +0530, Manivannan Sadhasivam wrote: > > > > On Mon, Jan 06, 2025 at 05:07:05PM -0600, Bjorn Helgaas wrote: > > > > > On Sun, Jan 05, 2025 at 03:46:12PM +0530, Manivannan Sadhasivam wrote: > > > > > > On Fri, Jan 03, 2025 at 03:05:31PM -0600, Bjorn Helgaas wrote: > > > > > > > On Thu, Mar 21, 2024 at 04:46:21PM +0530, Manivannan Sadhasivam wrote: > > > > > > > > On Qcom SoCs, the PCIe host bridge is connected to a single PCIe bridge > > > > > > > > for each controller instance. Hence, add a node to represent the bridge. > > > > > > > > > > > > > > > > Signed-off-by: Manivannan Sadhasivam > > > > > > > > --- > > > > > > > > arch/arm64/boot/dts/qcom/sm8250.dtsi | 30 ++++++++++++++++++++++++++++++ > > > > > > > > 1 file changed, 30 insertions(+) > > > > > > > > > > > > > > > > diff --git a/arch/arm64/boot/dts/qcom/sm8250.dtsi b/arch/arm64/boot/dts/qcom/sm8250.dtsi > > > > > > > > index 39bd8f0eba1e..fe5485256b22 100644 > > > > > > > > --- a/arch/arm64/boot/dts/qcom/sm8250.dtsi > > > > > > > > +++ b/arch/arm64/boot/dts/qcom/sm8250.dtsi > > > > > > > > @@ -2203,6 +2203,16 @@ pcie0: pcie@1c00000 { > > > > > > > > dma-coherent; > > > > > > > > > > > > > > > > status = "disabled"; > > > > > > > > + > > > > > > > > + pcie@0 { > > > > > > > > + device_type = "pci"; > > > > > > > > + reg = <0x0 0x0 0x0 0x0 0x0>; > > > > > > > > + bus-range = <0x01 0xff>; > > > > > > > > > > > > > > Hi Mani, most or all of the patches in this series add this > > > > > > > "bus-range" property. IIUC, these are all Root Ports and hence the > > > > > > > secondary/subordinate bus numbers should be programmable. > > > > > > > > > > > > Right. It is not a functional dependency. > > > > > > > > > > > > > If that's the case, I don't think we need to include "bus-range" in DT > > > > > > > for them, do we? > > > > > > > > > > > > We mostly include it to silence the below bindings check for the > > > > > > endpoint device node: > > > > > > > > > > > > Warning (pci_device_bus_num): /soc@0/pcie@1c00000/pcie@0/wifi@0: PCI bus number 1 out of range, expected (0 - 0) > > > > > > > > > > > > DTC check is happy if the 'bus-range' property is absent in the > > > > > > bridge node. But while validating the endpoint node (if defined), it > > > > > > currently relies on the parent 'bus-range' property to verify the > > > > > > bus number provided in the endpoint 'reg' property. > > > > > > > > > > > > I don't know else the check can verify the correctness of the > > > > > > endpoint bus number. So deferring to Rob here. > > > > > > > > > > I should know more about how this works in DT, but I don't. > > > > > > > > > > I guess https://git.kernel.org/linus/83d2a0a1e2b9 ("arm64: dts: qcom: > > > > > sm8250: Add PCIe bridge node") added this (subsequently renamed to > > > > > "pcieport0"): > > > > > > > > > > + pcie@0 { > > > > > + device_type = "pci"; > > > > > + reg = <0x0 0x0 0x0 0x0 0x0>; > > > > > + bus-range = <0x01 0xff>; > > > > > > > > > > which is used at places like > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/qrb5165-rb5.dts?id=v6.12#n788: > > > > > > > > > > &pcieport0 { > > > > > wifi@0 { > > > > > compatible = "pci17cb,1101"; > > > > > reg = <0x10000 0x0 0x0 0x0 0x0>; > > > > > > > > > > Based on > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pci/pci.txt?id=v6.12#n46 > > > > > (which is written for Root Ports and Switch Ports, but presumably > > > > > applies to endpoints like wifi as well), "reg" contains the device's > > > > > bus/device/function: > > > > > > > > > > - reg: > > > > > Identifies the PCI-PCI bridge. As defined in the IEEE Std 1275-1994 > > > > > document, it is a five-cell address encoded as (phys.hi phys.mid > > > > > phys.lo size.hi size.lo). phys.hi should contain the device's BDF as > > > > > 0b00000000 bbbbbbbb dddddfff 00000000. The other cells should be zero. > > > > > > > > > > So 0x10000 would decode to 01:00.0, which matches the <1 1> bus-range. > > > > > > > > > > I don't know the reason for requiring the BDF there, but the venerable > > > > > https://www.devicetree.org/open-firmware/bindings/pci/pci2_1.pdf, sec > > > > > 4.1.1, says "reg" is mandatory for PCI Child Nodes, and the first > > > > > entry must be the config space address (bus/device/function). > > > > > > > > > > I suppose maybe the BDF is needed to associate the properties with the > > > > > correct device, and if the OS were to reprogram the bridge secondary > > > > > bus number, it would have to remember the original value to preserve > > > > > this association. I don't think Linux *does* remember that, but it > > > > > also generally leaves the bridge bus numbers alone. > > > > > > > > Device drivers need to parse the properties defined in the device DT > > > > node. And the only way to identify the node is by using its 'reg' > > > > property which has the BDF identifier. This is common to other > > > > busses where the device address is encoded in the 'reg' property. > > > > > > Does this assume there is some firmware to configure these bridges > > > before Linux boots? > > > > No. > > > > > If bridges are completely unconfigured after > > > power-on, their secondary and subordinate bus numbers will be zero, so > > > a bus-range property for the bridge can only be an assumption about > > > what Linux will do. > > > > Secondary bus number for sure is not an assumption as it depends on > > the hardware topology which linux would know from DT. But > > subordinate number could be considered as an assumption. > > If there's no firmware and the secondary bus number is 0 when Linux > enumerates the bridge, does Linux know how to get the bus-range from > DT and program the bridge's secondary bus? > Linux doesn't seem to make use of the secondary bus number from DT node of a bridge, but there is no guarantee that other OSes making use of DT won't do. > And does Linux know how to update the subordinate bus number in the > case where several Root Ports specify 0xff in bus-range? > Same answer as above. - Mani -- மணிவண்ணன் சதாசிவம்