From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 330A13115BC; Wed, 15 Apr 2026 09:07:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776244037; cv=none; b=na45M0+Ra8Z8FVGViqmhk5a3xZKSo7UrLMu7qyobdesKXKDdzMxVbsbRsMsE2T2fJsR3mgOvmyu7ozo5B4x4Zei6nF8td4dgg36zUi4wwzsdVVm1S1kTvw1bk557R4ivgv4uZbvYPd3FAnO4jL4A8yQ0nvQSurIqz3mmyoHty7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776244037; c=relaxed/simple; bh=XHcFesqTcaOkSuOln4bQvIcKY4DyL9z2YyP7unLltzk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=krwbDui9KKDeJOFN2UJNpe6fVGZ5LacrvPk+7frVj52cgHqY5kJdoYOfk1ivzw4y/mMyD0PgSDH/yEDMPU/cc5fFcz8ItKVHMFRr84YoR+dTGOtb7p34EQYoXW2hixUPdkzroUka8RN4KZG/u+ug9ePJoJau2mj1abMfVbT8rko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=n4GZKgUQ; arc=none smtp.client-ip=198.175.65.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="n4GZKgUQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1776244036; x=1807780036; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=XHcFesqTcaOkSuOln4bQvIcKY4DyL9z2YyP7unLltzk=; b=n4GZKgUQqDMry7ukJAZ8CieW6miim0Ez8LYNOd0PJyViZDbqvY04EgjW fk7opFqlHvihbIYouIYPNWEEQ5OknfFNSur54PNfS5tS3QVkh4gp3ZvIP npdCa/oElsPXEOFskZrxR0pjNLBFgslor70ADJwq4i5dL6F0CXwwG9Ufg nftBwHN/IV7CsWRycl95iT33rOcr+7nMtDHyymo+jjtXFXlMGZue0DAPa gcF3A6X5HnAlqjp1fzCuxFUKR1pqPvl2I6NPXQLIA+EVOOPtR2Z8vMsUU 2kGy41FL7Bhg6oUmEZSh8snhRFBZRQ6pi5sR+z3sv9dYm4AHqyxk7ZP1q g==; X-CSE-ConnectionGUID: xBnssV7sQJGFWH/O+01xTw== X-CSE-MsgGUID: 4v8MOZs4T0iqz/qDk9I0rw== X-IronPort-AV: E=McAfee;i="6800,10657,11759"; a="88665396" X-IronPort-AV: E=Sophos;i="6.23,179,1770624000"; d="scan'208";a="88665396" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2026 02:07:15 -0700 X-CSE-ConnectionGUID: dig/invKSJuZ7wLgGQHR4w== X-CSE-MsgGUID: XwsoHjG9TAOScEITg4Ykxw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,179,1770624000"; d="scan'208";a="260786988" Received: from rvuia-mobl.ger.corp.intel.com (HELO localhost) ([10.245.244.34]) by orviesa002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2026 02:07:09 -0700 Date: Wed, 15 Apr 2026 12:07:06 +0300 From: Andy Shevchenko To: Chen-Yu Tsai Cc: Manivannan Sadhasivam , Manivannan Sadhasivam , Rob Herring , Greg Kroah-Hartman , Jiri Slaby , Nathan Chancellor , Nicolas Schier , Hans de Goede , Ilpo =?iso-8859-1?Q?J=E4rvinen?= , Mark Pearson , "Derek J. Clark" , Krzysztof Kozlowski , Conor Dooley , Marcel Holtmann , Luiz Augusto von Dentz , Bartosz Golaszewski , Bartosz Golaszewski , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-pm@vger.kernel.org, Stephan Gerhold , Dmitry Baryshkov , linux-acpi@vger.kernel.org, Hans de Goede , Bartosz Golaszewski , Luca Ceresoli Subject: Re: [PATCH v7 0/8] Add support for handling PCIe M.2 Key E connectors in devicetree Message-ID: References: <20260326-pci-m2-e-v7-0-43324a7866e6@oss.qualcomm.com> <20260413075459.GA2626902@google.com> Precedence: bulk X-Mailing-List: devicetree@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: Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo On Wed, Apr 15, 2026 at 04:31:24PM +0800, Chen-Yu Tsai wrote: > On Tue, Apr 14, 2026 at 8:03 PM Andy Shevchenko > wrote: > > On Tue, Apr 14, 2026 at 06:29:02PM +0800, Chen-Yu Tsai wrote: > > > On Tue, Apr 14, 2026 at 4:28 PM Andy Shevchenko > > > wrote: > > > > On Tue, Apr 14, 2026 at 01:03:19PM +0800, Chen-Yu Tsai wrote: > > > > > On Tue, Apr 14, 2026 at 12:08 AM Manivannan Sadhasivam wrote: > > > > > > On Mon, Apr 13, 2026 at 07:33:12PM +0530, Manivannan Sadhasivam wrote: > > > > > > > On Mon, Apr 13, 2026 at 03:54:59PM +0800, Chen-Yu Tsai wrote: > > > > > > > > On Thu, Mar 26, 2026 at 01:36:28PM +0530, Manivannan Sadhasivam wrote: ... > > > > > > > > - Given that this connector actually represents two devices, how do I > > > > > > > > say I want the BT part to be a wakeup source, but not the WiFi part? > > > > > > > > Does wakeup-source even work at this point? > > > > > > > > > > > > > > You can't use the DT property since the devices are not described in DT > > > > > > > statically. But you can still use the per-device 'wakeup' sysfs knob to enable > > > > > > > wakeup. > > > > > > > > > > I see. I think not being able to specify generic properties for the devices > > > > > on the connector is going to be a bit problematic. > > > > > > > > This is nature of the open-connectors, especially on the busses that are > > > > hotpluggable, like PCIe. We never know what is connected there _ahead_. > > > > > > I believe what you mean by "hotpluggable" is "user replaceable". > > > > From the OS perspective it's the same. From platform perspective > > there is a difference, granted. > > Yes. I just wanted to clarify. > > > > > In other words you can't describe in DT something that may not exist. > > > > > > But this is actually doable with the PCIe slot representation. The > > > properties are put in the device node for the slot. If no card is > > > actually inserted in the slot, then no device is created, and the > > > device node is left as not associated with anything. > > > > But you need to list all devices in the world if you want to support this > > Why would I need to? The PCIe slot representation just describes a > PCIe bridge. Granted this might not be entirely correct, but it's > what we currently have. > > And even then, there are properties like memory-region or wakeup-source > that are generic and aren't tied to specific devices. Yes, see below what I replied... > > somehow. Yes, probably many of them (or majority) will be enumerated as is, ^^^ "the majority" will work without any assistance. > > but some may need an assistance via (dynamic) properties or similar mechanisms. > Even if we wanted to add dynamic properties, there is currently no proper > device node to attach them to. Isn't that's node created dynamically as well and attached to the PCI bus? > > > It's just that for this new M.2 E-key connector, there aren't separate > > > nodes for each interface. And the system doesn't associate the device > > > node with the device, because it's no longer a child node of the > > > controller or hierarchy, but connected over the OF graph. > > > > > > Moving over to the E-key connector representation seems like one step > > > forward and one step backward in descriptive ability. We gain proper > > > power sequencing, but lose generic properties. > > > > The "key" is property of the connector. Hence if you have an idea what can be > > common for ALL "key":s, that's probably can be abstracted. Note, I'm not > > familiar with the connector framework in the Linux kernel, perhaps it's already > > that kind of abstraction. > > I'm not arguing for a even more generic "M.2" connector. The "key" is > already described in the compatible. I'm saying we should have some way > of describing the individual interfaces (PCIe, SDIO, USB, UART, I2S, I2C) > on the connector so further nodes or properties can be attached to them, > either with overlays or dynamically within the kernel. Right now the > are only described as individual ports, but we can't actually tie a > device to a OF graph port. Shouldn't it be described as a DT subtree? Sorry, I am not familiar with DT enough to understand the issue you have. > But maybe I'm overthinking the representation part. AFAICT for Qualcomm's > UART-based BT bit part, Mani just had the driver create a device node > under the UART (by traversing the OF graph to find the UART). If that's > the desired way then the connector binding should mention it. And that > works for me. But I think it's messier and also we're missing an > opportunity to make the M.2 connector a standardized attachment point > for overlays. Okay, now it might get clearer to me, but still, I am not an expert. > Mani, could you also chime in a bit on what you envisioned? +1, please elaborate to me as well. > (Added Luca from Bootlin to CC, as I think there are parallels to the > "Hotplug of Non-discoverable Hardware" work) > > > > The latter part is solvable, but we likely need child nodes under the > > > connector for the different interfaces. Properties that make sense for > > > one type might not make sense for another. > > > > > > P.S. We could also just add child device nodes under the controller to > > > put the generic properties, but that's splitting the description into > > > multiple parts. Let's not go there if at all possible. -- With Best Regards, Andy Shevchenko