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

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Message-ID: <20240904201134.GA345594@bhelgaas>
Date: Wed, 4 Sep 2024 15:11:34 -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,
	Jonathan.Cameron@...wei.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,
	bhelgaas@...gle.com, lukas@...ner.de, paul.e.luse@...el.com,
	jing2.liu@...el.com
Subject: Re: [PATCH V4 09/12] PCI/TPH: Add save/restore support for TPH

On Thu, Aug 22, 2024 at 03:41:17PM -0500, Wei Huang wrote:
> From: Paul Luse <paul.e.luse@...ux.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
>