From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bmailout2.hostsharing.net (bmailout2.hostsharing.net [83.223.78.240]) (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 4FD122FDC5B for ; Wed, 12 Nov 2025 09:50:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=83.223.78.240 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762941014; cv=none; b=r5I49P4rEn3i88IFltqQod0bxl5msxP9H81jmXH3qBKAq8VjSA4jXbtNUX1SJ6lTDi6pXHk/R3jYM7eSq7BVdwLo/xyhOxFfCA9LMDY2GnKqPSMjI0Nm64E1TQdWblgidnRu+3ws5jY+ME2KcoUanfYaOgXw07+62PJFGy2IQQo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762941014; c=relaxed/simple; bh=pWaoinVZH7rlrVoExU+UXZcijLxigr8ftAiDGCtifQQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RfE5cJg3WX/5aodezP57RWT0aTzENO1EG7dmLQME8ZLtHz7nQwA7qwGEOmT+w1Hm/cobIz7LLjcQuctlwwEt7iA9lr+RxYSl63ESU1CsENxSo5YT3JsE7zT8PYYhZlGcOAo3CKGUr6g3ohNzXz0L6NIxIzVxnPGE6fdIPMEwzWA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de; spf=none smtp.mailfrom=h08.hostsharing.net; arc=none smtp.client-ip=83.223.78.240 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=h08.hostsharing.net Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1) server-digest SHA384 client-signature ECDSA (secp384r1) client-digest SHA384) (Client CN "*.hostsharing.net", Issuer "GlobalSign GCC R6 AlphaSSL CA 2025" (verified OK)) by bmailout2.hostsharing.net (Postfix) with ESMTPS id CA721200C2E1; Wed, 12 Nov 2025 10:50:01 +0100 (CET) Received: by h08.hostsharing.net (Postfix, from userid 100393) id BD4D8137E4; Wed, 12 Nov 2025 10:50:01 +0100 (CET) Date: Wed, 12 Nov 2025 10:50:01 +0100 From: Lukas Wunner To: Bjorn Helgaas Cc: Mika Westerberg , linux-pci@vger.kernel.org Subject: Re: [PATCH v4] PCI/PTM: Enable PTM only if it advertises a role Message-ID: References: <20251111061048.681752-1-mika.westerberg@linux.intel.com> <20251111153942.GA2174680@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251111153942.GA2174680@bhelgaas> On Tue, Nov 11, 2025 at 09:39:42AM -0600, Bjorn Helgaas wrote: > I do wonder about the fact that previously we automatically enabled > PTM only for Root Ports and Switch Upstream Ports, but we didn't > enable it for Endpoints until a driver called pci_enable_ptm(). > > With this change, it looks like we automatically enable PTM for every > device that supports it. Worth a mention in the commit log, and we > might also want to revisit the drivers (ice, idpf, igc, mlx5) that > explicitly enable it to remove the enable and disable calls there. > > PTM consumes some link bandwidth, so the idea was to avoid paying that > cost unless a driver actually wanted to use PTM. pci_pm_suspend() and pci_pm_runtime_suspend() call pci_suspend_ptm() and there's a code comment preceding the call that it allows platforms such as Intel Coffee Lake to go to a deeper power state. So apparently PTM not only has a bandwidth cost but also a power cost. Thanks, Lukas