From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793468434; b=A0q8R7beusEZTZ0EYWz6fY84YC4QLyMrHRKOQIOmWb4ppvmmAP/QjvfxjXhdJdRrErhl KdLCJYKrEpJ9fqClX1m9UvWkYABMIYT2p+R8O5s+pA/bMTBAWJuODyai+ZcQ9i7hXUqgE rI/j6ljaoR3ls5WtgR/sJLtZtITwEID5mawQm2XkqaQvdF/Fx5fHrecpD7s6wrwpUIqIM 8wmltHp40W2Qx7ckdsfVUTH4aglUIyLx46AUs3md8NtxuRWBWcxgwCL8f24qDe0SJdU3s 9cX4XVlqV+CDeDGKGZygAa9frFbA2uEB68Kqdlta2+ADXnP5sN6XTgLqwn1z+DzcYEA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793468434; h=Received:DKIM-Signature:MIME-Version:Content-Type: Content-Transfer-Encoding:Subject:From:To:Cc:In-Reply-To:References: Date:Message-Id:X-Mailer:X-Developer-Signature:X-Developer-Key; bh=+7k1NaGz5TOnOiTpgvvEXdv7k27RwmSfbCON8FW0kxw=; b=SxDQRZkKnpexya9mbt4/pkpJBskt459auzH+lbZI1y6SBxm1IDHUeuHA93LVfUQ0ZUI9 lWr3sKRadofcSco3mz4ZWp6RiPmGh993EXYI9iZfxdsuc6AU67awZ5rpQJ+34LahvKFPi bF5B5K+YTG8WLHXSTTUObTANup+g6SgegrFZobD1kjS0qBpbaQVQmmzrPRLH4elkPcfiA sPgXWyfCQ6BLP+KPXTNztmFPiJuZIUBRz9gO2eyUCBsCtn+WhYXnuHOG4vP25+XTBU3Ky LuqEVGdpYF6CvAQcrmyg0popW46uR1gKwGNJ49tVWtikdX8mVUR5XXX4vvsFyUBwu7g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="JDN8500/"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D359B606A31C; Sat, 31 Oct 2026 17:40:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=JDN8500/ Received: by smtp.kernel.org (Postfix) with ESMTPSA id A38571F000C1; Sat, 31 Oct 2026 17:40:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793468433; bh=+7k1NaGz5TOnOiTpgvvEXdv7k27RwmSfbCON8FW0kxw=; h=Subject:From:To:Cc:In-Reply-To:References:Date; b=JDN8500/3P01cYmIsV8CpwYjOiXOUz0EXUq3PVUNx3UQEgfh079uahNBYdsdnp7xd 9Z0PxyBRM0ydrsTs18AviGmMAR/WZ2bgPvgHQa5LgMWMQEnJmC2s0GllDuEHOXUG5m tQG3Q7Fcz7mFT3Xm36W+WChrVIO1gvC1aERSBIc/bUjif+jXwykHli1gmykhSNXjts h0E9r/kk4a1J3B+/QyTs56S4JwipW8ZK4WahKjbdMLm4uc/L8/T6k/n7Sa/m95XGvP PTNbkjtJibfDvtEceuvAC6lbElu8kpf35yeFtzfc7hdF3//I9B5z9XYff6hIYLQle+ 7m4LvgHHUrtiA== X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [PATCH] Revert "phy: qcom: qmp-pcie: Skip PHY reset if already up" From: Manivannan Sadhasivam To: Michael Burch Cc: Vinod Koul , Neil Armstrong , Manivannan Sadhasivam , Krishna Chaitanya Chundru , Qiang Yu , Konrad Dybcio , Abel Vesa , Bjorn Andersson , Hans de Goede , linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev In-Reply-To: <20261013-qmp-pcie-skip-reset-revert-v1@michaelburch.net> References: <20261013-qmp-pcie-skip-reset-revert-v1@michaelburch.net> Date: Sat, 31 Oct 2026 23:10:21 +0530 Message-Id: <179346842169.7309.953613001579327741.b4-reply@b4> X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2212; i=mani@kernel.org; h=from:subject:message-id; bh=MIzTd1itZPpW7FCl5YwWGtQIeJPAAhpsZ38f5D6eUQU=; b=owGbwMvMwMUYOl/w2b+J574ynlZLYsh6psGZ4fnkq2XWt7t1x7msGUP7WBYY5yqy6uRa+v+1D dVMnDalk9GYhYGRi0FWTJElfamzVqPH6RtLItSnwwxiZQKZwsDFKQATCZrBwTBj5WLWvc4VcisS HaoYj84p8Iyq+C3byiB894p1mfriqZVXfiSpSQv7X9OdwHvsn51Je96ctn+a0XcktNxffSgp4l4 o45OS6VmeX/3vQPGjvXY2bJKbMn4fzQuZlvHaxnEzy5ffMQlx84S/JStMvHohTDugymCnh/raSF 9fg2522fs8+5mtn3n9Uwq7dWvBU5kdDxccYJ+0u7lO9a2NuUZm4vP2D2+Y1n223Tmhf1HMLDvXm Plz1Z6wPWMV08l5fOLU0fi4f3/DZBQPmp/mTA8oLw9I1nvQoVq0Uvx6lK6OVzXfid5phXsvu3us U7RMbcjQ4g6dNGcdy1XedSyldpKPyyTP7hRZclvV418VAA== X-Developer-Key: i=mani@kernel.org; a=openpgp; fpr=C668AEC3C3188E4C611465E7488550E901166008 On 2026-10-13 09:22 -0500, Michael Burch wrote: > This reverts commit 910b828b22b7b91054b3bd4be676a017444b0e00. > > That commit skips the no-csr reset assert/deassert (and the 200-300us > settle) whenever the bootloader already brought the PCIe QMP PHY up: > > skip_reset = qmp->skip_init && > !qphy_checkbits(pcs, cfg->regs[QPHY_PCS_STATUS], > cfg->phy_status); > > and states its own assumption explicitly: "This relies on the assumption > that when skip_init is enabled and the PHY is reported as up, the > bootloader has already configured the PHY correctly and the link is in a > usable state." > > That assumption does not hold on the Dell XPS 13 9345 (X1E80100). UEFI > boots from the NVMe behind pcie6a, so the PHY is always already started > when Linux takes over, skip_init is true, and the reset is skipped. The > link then never retrains and the root port comes up with no endpoint: > > qcom-pcie 1bf8000.pcie: Device found, but not active > pci 0006:00:00.0: [17cb:0111] type 01 class 0x060400 PCIe Root Port > (no 0006:01:00.0, no nvme at all) > > "Device found, but not active" is dw_pcie_wait_for_link() reporting LTSSM > stuck in POLL.Active/POLL.Compliance -- receiver detected, training never > completes -- so the machine cannot find its root filesystem and drops to > a dracut emergency shell. v7.2 is unaffected because it always performed > the reset. > > The commit was applied on its own as patch 1/4 of "PCI: qcom: Add link > retention support"; 2/4-4/4 have not landed. Without them, > qcom_pcie_host_init() still asserts PERST# and resets the controller > before qcom_pcie_phy_power_on(), so the link is down while > QPHY_PCS_STATUS still reports the bootloader's state, and the skip's > precondition never holds. Revert it until the rest of the series lands. > Ouch. This dependency should've been mentioned in the cover letter of the offending series :/ > Fixes: 910b828b22b7 ("phy: qcom: qmp-pcie: Skip PHY reset if already up") > Signed-off-by: Michael Burch Reviewed-by: Manivannan Sadhasivam - Mani