linux-kernel - Re: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM configuration

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Message-ID: <8888528f-db70-1fef-71bb-8a3dd1f4380f@linux.intel.com>
Date:   Thu, 26 Jan 2023 13:22:40 -0800
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Vidya Sagar <vidyas@...dia.com>, bhelgaas@...gle.com,
        rafael.j.wysocki@...el.com, kai.heng.feng@...onical.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        treding@...dia.com, jonathanh@...dia.com, kthota@...dia.com,
        mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM
 configuration

Hi,

On 1/25/23 5:38 AM, Vidya Sagar wrote:
> Many PCIe device drivers save the configuration state of their respective
> devices during probe and restore the same when their 'slot_reset' hook
> is called through PCIe Error Recovery System.
> If the system has a change in ASPM policy after the driver's probe is
> called and before error event occurred, 'slot_reset' hook restores the
> PCIe configuration state to what it was at the time of probe but not with
> what it was just before the occurrence of the error event.
> This effectively leads to a mismatch in the ASPM configuration between
> the device and its upstream parent device.
> This patch addresses that issue by updating the saved configuration state
> of the device with the latest info whenever there is a change w.r.t ASPM
> policy.

Do we need two save/restore calls for ASPM function? Is it not possible
to extend pci_save_aspm_l1ss_state() to meet your need?

> 
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> ---
>  drivers/pci/pci.h       |  4 ++++
>  drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 9ed3b5550043..f4a91d4fe96d 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -566,12 +566,16 @@ bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
>  void pcie_aspm_init_link_state(struct pci_dev *pdev);
>  void pcie_aspm_exit_link_state(struct pci_dev *pdev);
>  void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
> +void pci_save_aspm_state(struct pci_dev *dev);
> +void pci_restore_aspm_state(struct pci_dev *dev);
>  void pci_save_aspm_l1ss_state(struct pci_dev *dev);
>  void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
>  #else
>  static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
>  static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
>  static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
> +static inline void pci_save_aspm_state(struct pci_dev *dev) { }
> +static inline void pci_restore_aspm_state(struct pci_dev *dev) { }
>  static inline void pci_save_aspm_l1ss_state(struct pci_dev *dev) { }
>  static inline void pci_restore_aspm_l1ss_state(struct pci_dev *dev) { }
>  #endif
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 53a1fa306e1e..f25e0440d36b 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -151,6 +151,7 @@ static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
>  						   PCI_EXP_LNKCTL_CLKREQ_EN,
>  						   val);
>  	link->clkpm_enabled = !!enable;
> +	pci_save_aspm_state(child);

Add some details about this change to the commit log. Currently, you have talked only
about the ASPM policy change issue.

>  }
>  
>  static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
> @@ -757,6 +758,39 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
>  				PCI_L1SS_CTL1_L1SS_MASK, val);
>  }
>  
> +void pci_save_aspm_state(struct pci_dev *dev)
> +{
> +	int i = 0;
> +	struct pci_cap_saved_state *save_state;
> +	u16 *cap;
> +
> +	if (!pci_is_pcie(dev))
> +		return;
> +
> +	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
> +	if (!save_state)
> +		return;
> +
> +	cap = (u16 *)&save_state->cap.data[0];
> +	i++;
> +	pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[i++]);
> +}
> +
> +void pci_restore_aspm_state(struct pci_dev *dev)
> +{
> +	int i = 0;
> +	struct pci_cap_saved_state *save_state;
> +	u16 *cap;
> +
> +	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
> +	if (!save_state)
> +		return;
> +
> +	cap = (u16 *)&save_state->cap.data[0];
> +	i++;
> +	pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
> +}
> +

Don't you need to add this restore call in pci_restore_state()?

>  void pci_save_aspm_l1ss_state(struct pci_dev *dev)
>  {
>  	struct pci_cap_saved_state *save_state;
> @@ -849,6 +883,12 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
>  		pcie_config_aspm_dev(parent, upstream);
>  
>  	link->aspm_enabled = state;
> +
> +	/* Update latest ASPM configuration in saved context */
> +	pci_save_aspm_state(link->downstream);
> +	pci_save_aspm_l1ss_state(link->downstream);
> +	pci_save_aspm_state(parent);
> +	pci_save_aspm_l1ss_state(parent);
>  }
>  
>  static void pcie_config_aspm_path(struct pcie_link_state *link)

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer