From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 80133500952; Fri, 9 Jan 2026 15:53:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767974032; cv=none; b=H2/GdcGonFGtvUpU6AjMlKNIt1qHoQqpNsMrSYYbMTbd2+UpCOFs2TelmjUhZ2asN3/qCbRD0qISriL4S5PuFQre9u8KOY1DpTAeCxb+Sh0RCml3B7dcW4z/7cfDGOrHRC/OhBdfEih7YHE5aN0jT22lAjkK9yc+N8xUI2zeG30= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767974032; c=relaxed/simple; bh=zK0zjHRUg0EscVVeO0n2jsonL23Wr5elXJuCtQlfIvk=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=EtrV1bZr+9dNHNIHn6BZTKf3pPnuxW0HURktC77dd+kv1uZOkV8GXRDi8SUK7PFT0QI1w+N5pbOk65rF/Oz1iUkMegrxAAKM4P6G5fEtE55xxeQp+cguxpmBJ2C4Re7ethSnE1D9RBlj2K2NRSVXyd9/GMSlLxYR/xZdNcIWYeM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nhdOUxd1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nhdOUxd1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06978C4CEF1; Fri, 9 Jan 2026 15:53:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767974032; bh=zK0zjHRUg0EscVVeO0n2jsonL23Wr5elXJuCtQlfIvk=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=nhdOUxd1lM18hERN+FcC1kmau3i2OjE4BlxSBRaiAzLUMZv1JsAEAbAjHgrRHrdD+ AsPy6IDmAIInpzBYpN6EEwRhmi7oP9XRmoShYZ4o0BgSPgAJNXRVNtEEr9Jk3sjoBk cqqaPPoRDuidy47fVBzdphqqnG4yZkmwvSiSFIdpvNV3bKdZUEhdogogHqhZqfWk2V SCpG/goOIC+C2cbwH4qji80ADLcLZt7gJzQyV3bEkaEbph3Yo0LLo0//4iMW/a3D/X xMOTj0Yxs4AcQM/dumYzVEcza1O0YfbqVUfL4M0kHjubZd88mAbiR6zHKiGoH2eKWQ NUjY7Cuy1q7bQ== Date: Fri, 9 Jan 2026 09:53:50 -0600 From: Bjorn Helgaas To: Krishna Chaitanya Chundru Cc: Vinod Koul , Neil Armstrong , Philipp Zabel , Jingoo Han , Manivannan Sadhasivam , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas , linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH 2/5] PCI: dwc: Add support for retaining link during host init Message-ID: <20260109155350.GA546142@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: <20260109-link_retain-v1-2-7e6782230f4b@oss.qualcomm.com> On Fri, Jan 09, 2026 at 12:51:07PM +0530, Krishna Chaitanya Chundru wrote: > Some platforms keep the PCIe link up across bootloader and kernel > handoff. In such cases, reinitializing the root complex is unnecessary > if the DWC glue drivers wants to retain the PCIe link. > > Introduce a link_retain flag in struct dw_pcie_rp to indicate that > the link should be preserved. When this flag is set by DWC glue drivers, > skip dw_pcie_setup_rc() and only initialize MSI, avoiding redundant > configuration steps. It sounds like this adds an assumption that the bootloader initialization is the same as what dw_pcie_setup_rc() would do. This assumption also applies to future changes in dw_pcie_setup_rc(). It looks like you mention an issue like this in [PATCH 4/5]; DBI & ATU base being different than "HLOS" (whatever that is). This sounds like a maintenance issue keeping bootloader and kernel driver assumptions synchronized. Is there something in dw_pcie_setup_rc() that takes a lot of time or forces a link retrain? You mentioned some clock and GENPD issues in the cover letter, but I don't see the connection between those and dw_pcie_setup_rc(). If there is a connection, please include it in this commit log and include a code comment about why dw_pcie_setup_rc() is being skipped. > Signed-off-by: Krishna Chaitanya Chundru > --- > drivers/pci/controller/dwc/pcie-designware-host.c | 11 ++++++++--- > drivers/pci/controller/dwc/pcie-designware.h | 1 + > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > index 372207c33a857b4c98572bb1e9b61fa0080bc871..d050df3f22e9507749a8f2fedd4c24fca43fb410 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > @@ -655,9 +655,14 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > if (ret) > goto err_free_msi; > > - ret = dw_pcie_setup_rc(pp); > - if (ret) > - goto err_remove_edma; > + if (!pp->link_retain) { Use positive logic if possible (test "pp->link_retain" instead of "!pp->link_retain"). I suspect this would be more maintainable if you identified specific things *inside* dw_pcie_setup_rc() that need to be skipped, and you added tests there. > + ret = dw_pcie_setup_rc(pp); > + if (ret) > + goto err_remove_edma; > + } else { > + dw_pcie_msi_init(pp); > + } > + > > if (!dw_pcie_link_up(pci)) { > ret = dw_pcie_start_link(pci); > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > index 31685951a080456b8834aab2bf79a36c78f46639..8acab751b66a06e8322e027ab55dc0ecfdcf634c 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -439,6 +439,7 @@ struct dw_pcie_rp { > struct pci_config_window *cfg; > bool ecam_enabled; > bool native_ecam; > + bool link_retain; > }; > > struct dw_pcie_ep_ops { > > -- > 2.34.1 >