Re: [PATCH V5 1/5] PCI: Add TLP Processing Hints (TPH) support

[Simon Horman <horms@kernel.org>]

On Mon, Sep 16, 2024 at 03:50:59PM -0500, Wei Huang wrote:
> Add support for PCIe TLP Processing Hints (TPH) support (see PCIe r6.2,
> sec 6.17).
> 
> Add missing TPH register definitions in pci_regs.h, including the TPH
> Requester capability register, TPH Requester control register, TPH
> Completer capability, and the ST fields of MSI-X entry.
> 
> Introduce pcie_enable_tph() and pcie_disable_tph(), enabling drivers to
> toggle TPH support and configure specific ST mode as needed. Also add a
> new kernel parameter, "pci=notph", allowing users to disable TPH support
> across the entire system.
> 
> Co-developed-by: Jing Liu <jing2.liu@intel.com>
> Signed-off-by: Jing Liu <jing2.liu@intel.com>
> Co-developed-by: Paul Luse <paul.e.luse@linux.intel.com>
> Signed-off-by: Paul Luse <paul.e.luse@linux.intel.com>
> Co-developed-by: Eric Van Tassell <Eric.VanTassell@amd.com>
> Signed-off-by: Eric Van Tassell <Eric.VanTassell@amd.com>
> Signed-off-by: Wei Huang <wei.huang2@amd.com>
> Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
> Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
> Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Lukas Wunner <lukas@wunner.de>

...

> diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c

...

> +/**
> + * pcie_enable_tph - Enable TPH support for device using a specific ST mode
> + * @pdev: PCI device
> + * @mode: ST mode to enable. Current supported modes include:
> + *
> + *   - PCI_TPH_ST_NS_MODE: NO ST Mode
> + *   - PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
> + *   - PCI_TPH_ST_DS_MODE: Device Specific Mode
> + *
> + * Checks whether the mode is actually supported by the device before enabling
> + * and returns an error if not. Additionally determines what types of requests,
> + * TPH or extended TPH, can be issued by the device based on its TPH requester
> + * capability and the Root Port's completer capability.
> + *
> + * Return: 0 on success, otherwise negative value (-errno)
> + */
> +int pcie_enable_tph(struct pci_dev *pdev, int mode)
> +{
> +	u32 reg;
> +	u8 dev_modes;
> +	u8 rp_req_type;
> +
> +	/* Honor "notph" kernel parameter */
> +	if (pci_tph_disabled)
> +		return -EINVAL;
> +
> +	if (!pdev->tph_cap)
> +		return -EINVAL;
> +
> +	if (pdev->tph_enabled)
> +		return -EBUSY;
> +
> +	/* Sanitize and check ST mode comptability */

Hi Wei Huang, all,

Another minor nit from my side (the last one, I think):

comptability -> compatibility

Flagged by checkpatch.pl --codespell

> +	mode &= PCI_TPH_CTRL_MODE_SEL_MASK;
> +	dev_modes = get_st_modes(pdev);
> +	if (!((1 << mode) & dev_modes))
> +		return -EINVAL;
> +
> +	pdev->tph_mode = mode;
> +
> +	/* Get req_type supported by device and its Root Port */
> +	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
> +	if (FIELD_GET(PCI_TPH_CAP_EXT_TPH, reg))
> +		pdev->tph_req_type = PCI_TPH_REQ_EXT_TPH;
> +	else
> +		pdev->tph_req_type = PCI_TPH_REQ_TPH_ONLY;
> +
> +	rp_req_type = get_rp_completer_type(pdev);
> +
> +	/* Final req_type is the smallest value of two */
> +	pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type);
> +
> +	if (pdev->tph_req_type == PCI_TPH_REQ_DISABLE)
> +		return -EINVAL;
> +
> +	/* Write them into TPH control register */
> +	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, &reg);
> +
> +	reg &= ~PCI_TPH_CTRL_MODE_SEL_MASK;
> +	reg |= FIELD_PREP(PCI_TPH_CTRL_MODE_SEL_MASK, pdev->tph_mode);
> +
> +	reg &= ~PCI_TPH_CTRL_REQ_EN_MASK;
> +	reg |= FIELD_PREP(PCI_TPH_CTRL_REQ_EN_MASK, pdev->tph_req_type);
> +
> +	pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, reg);
> +
> +	pdev->tph_enabled = 1;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(pcie_enable_tph);

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