linux-kernel - Re: [PATCH V2 4/9] PCI/TPH: Implement a command line option to force No ST Mode

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Message-ID: <20240607174237.GA853301@bhelgaas>
Date: Fri, 7 Jun 2024 12:42:37 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Wei Huang <wei.huang2@....com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, netdev@...r.kernel.org,
	bhelgaas@...gle.com, corbet@....net, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	alex.williamson@...hat.com, gospo@...adcom.com,
	michael.chan@...adcom.com, ajit.khaparde@...adcom.com,
	somnath.kotur@...adcom.com, andrew.gospodarek@...adcom.com,
	manoj.panicker2@....com, Eric.VanTassell@....com,
	vadim.fedorenko@...ux.dev, horms@...nel.org, bagasdotme@...il.com
Subject: Re: [PATCH V2 4/9] PCI/TPH: Implement a command line option to force
 No ST Mode

On Fri, May 31, 2024 at 04:38:36PM -0500, Wei Huang wrote:
> When "No ST mode" is enabled, end-point devices can generate TPH headers
> but with all steering tags treated as zero. A steering tag of zero is
> interpreted as "using the default policy" by the root complex. This is
> essential to quantify the benefit of steering tags for some given
> workloads.

>  #ifdef CONFIG_PCIE_TPH
>  int pcie_tph_disable(struct pci_dev *dev);
> +int tph_set_dev_nostmode(struct pci_dev *dev);

Exported functions need a "pci" or "pcie_" prefix.  We haven't been
completely consistent on this; we have "pci_acs_*", which is obviously
PCIe-specific, but we do also have pcie_find_root_port() etc.