Re: [PATCH v2 1/2] Add save/restore of Precision Time Measurement capability

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Dec 07, 2020 at 02:39:50PM -0800, David E. Box wrote:
> The PCI subsystem does not currently save and restore the configuration
> space for the Precision Time Measurement (PTM) PCIe extended capability
> leading to the possibility of the feature returning disabled on S3 resume.
> This has been observed on Intel Coffee Lake desktops. Add save/restore of
> the PTM control register. This saves the PTM Enable, Root Select, and
> Effective Granularity bits.
> 
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Signed-off-by: David E. Box <david.e.box@linux.intel.com>

Applied both to pci/ptm for v5.11, thanks!

> ---
> 
> Changes from V1:
> 	- Move save/restore functions to ptm.c
> 	- Move pci_add_ext_cap_sve_buffer() to pci_ptm_init in ptm.c
> 	
>  drivers/pci/pci.c      |  2 ++
>  drivers/pci/pci.h      |  8 ++++++++
>  drivers/pci/pcie/ptm.c | 43 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 53 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e578d34095e9..12ba6351c05b 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1566,6 +1566,7 @@ int pci_save_state(struct pci_dev *dev)
>  	pci_save_ltr_state(dev);
>  	pci_save_dpc_state(dev);
>  	pci_save_aer_state(dev);
> +	pci_save_ptm_state(dev);
>  	return pci_save_vc_state(dev);
>  }
>  EXPORT_SYMBOL(pci_save_state);
> @@ -1677,6 +1678,7 @@ void pci_restore_state(struct pci_dev *dev)
>  	pci_restore_vc_state(dev);
>  	pci_restore_rebar_state(dev);
>  	pci_restore_dpc_state(dev);
> +	pci_restore_ptm_state(dev);
>  
>  	pci_aer_clear_status(dev);
>  	pci_restore_aer_state(dev);
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index f86cae9aa1f4..62cdacba5954 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -516,6 +516,14 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
>  
>  #endif /* CONFIG_PCI_IOV */
>  
> +#ifdef CONFIG_PCIE_PTM
> +void pci_save_ptm_state(struct pci_dev *dev);
> +void pci_restore_ptm_state(struct pci_dev *dev);
> +#else
> +static inline void pci_save_ptm_state(struct pci_dev *dev) {}
> +static inline void pci_restore_ptm_state(struct pci_dev *dev) {}
> +#endif
> +
>  unsigned long pci_cardbus_resource_alignment(struct resource *);
>  
>  static inline resource_size_t pci_resource_alignment(struct pci_dev *dev,
> diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> index 357a454cafa0..6b24a1c9327a 100644
> --- a/drivers/pci/pcie/ptm.c
> +++ b/drivers/pci/pcie/ptm.c
> @@ -29,6 +29,47 @@ static void pci_ptm_info(struct pci_dev *dev)
>  		 dev->ptm_root ? " (root)" : "", clock_desc);
>  }
>  
> +void pci_save_ptm_state(struct pci_dev *dev)
> +{
> +	int ptm;
> +	struct pci_cap_saved_state *save_state;
> +	u16 *cap;
> +
> +	if (!pci_is_pcie(dev))
> +		return;
> +
> +	ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
> +	if (!ptm)
> +		return;
> +
> +	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
> +	if (!save_state) {
> +		pci_err(dev, "no suspend buffer for PTM\n");
> +		return;
> +	}
> +
> +	cap = (u16 *)&save_state->cap.data[0];
> +	pci_read_config_word(dev, ptm + PCI_PTM_CTRL, cap);
> +}
> +
> +void pci_restore_ptm_state(struct pci_dev *dev)
> +{
> +	struct pci_cap_saved_state *save_state;
> +	int ptm;
> +	u16 *cap;
> +
> +	if (!pci_is_pcie(dev))
> +		return;
> +
> +	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
> +	ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM);
> +	if (!save_state || !ptm)
> +		return;
> +
> +	cap = (u16 *)&save_state->cap.data[0];
> +	pci_write_config_word(dev, ptm + PCI_PTM_CTRL, *cap);
> +}
> +
>  void pci_ptm_init(struct pci_dev *dev)
>  {
>  	int pos;
> @@ -65,6 +106,8 @@ void pci_ptm_init(struct pci_dev *dev)
>  	if (!pos)
>  		return;
>  
> +	pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_PTM, sizeof(u16));
> +
>  	pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
>  	local_clock = (cap & PCI_PTM_GRANULARITY_MASK) >> 8;
>  
> -- 
> 2.20.1
>