Re: [PATCH V4 09/12] PCI/TPH: Add save/restore support for TPH

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Aug 22, 2024 at 03:41:17PM -0500, Wei Huang wrote:
> From: Paul Luse <paul.e.luse@linux.intel.com>
> 
> Save and restore the configuration space for TPH capability to preserve
> the settings during PCI reset. The settings include the TPH control
> register and the ST table if present.

> +void pci_restore_tph_state(struct pci_dev *pdev)
> +{
> +	struct pci_cap_saved_state *save_state;
> +	int num_entries, i, offset;
> +	u16 *st_entry;
> +	u32 *cap;
> +
> +	if (!pdev->tph_cap)
> +		return;
> +
> +	if (!pdev->tph_enabled)
> +		return;
> +
> +	save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
> +	if (!save_state)
> +		return;
> +
> +	/* Restore control register and all ST entries */
> +	cap = &save_state->cap.data[0];
> +	pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, *cap++);
> +	st_entry = (u16 *)cap;
> +	offset = PCI_TPH_BASE_SIZEOF;
> +	num_entries = get_st_table_size(pdev);
> +	for (i = 0; i < num_entries; i++) {
> +		pci_write_config_word(pdev, pdev->tph_cap + offset,
> +				      *st_entry++);
> +		offset += sizeof(u16);
> +	}
> +}
> +
> +void pci_save_tph_state(struct pci_dev *pdev)
> +{
> +	struct pci_cap_saved_state *save_state;
> +	int num_entries, i, offset;
> +	u16 *st_entry;
> +	u32 *cap;
> +
> +	if (!pdev->tph_cap)
> +		return;
> +
> +	if (!pdev->tph_enabled)
> +		return;
> +
> +	save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
> +	if (!save_state)
> +		return;

Don't we need a pci_add_ext_cap_save_buffer() somewhere for this?
E.g., in pci_tph_init()?

> +	/* Save control register */
> +	cap = &save_state->cap.data[0];
> +	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, cap++);
> +
> +	/* Save all ST entries in extended capability structure */
> +	st_entry = (u16 *)cap;
> +	offset = PCI_TPH_BASE_SIZEOF;
> +	num_entries = get_st_table_size(pdev);
> +	for (i = 0; i < num_entries; i++) {
> +		pci_read_config_word(pdev, pdev->tph_cap + offset,
> +				     st_entry++);
> +		offset += sizeof(u16);
> +	}
> +}
> +
>  void pci_tph_init(struct pci_dev *pdev)
>  {
>  	pdev->tph_cap = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_TPH);
> -- 
> 2.45.1
>