linux-kernel - Re: [PATCH V4] PCI/ASPM: Update saved buffers with latest ASPM

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Message-ID: <83f0d77b-8ea4-4443-8077-6139bc905952@linux.intel.com>
Date: Thu, 22 Feb 2024 10:20:06 -0800
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Vidya Sagar <vidyas@...dia.com>, bhelgaas@...gle.com, macro@...am.me.uk,
 ajayagarwal@...gle.com, ilpo.jarvinen@...ux.intel.com,
 david.e.box@...ux.intel.com, hkallweit1@...il.com, johan+linaro@...nel.org,
 xueshuai@...ux.alibaba.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 V4] PCI/ASPM: Update saved buffers with latest ASPM


On 2/22/24 9:44 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 Handler.
>
> 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 to
> 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.
>
> Update the saved configuration state of the device with the latest info
> whenever there is a change w.r.t ASPM policy.
>
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> ---
> V4:
> * Rebased on top of pci/aspm branch
>
> V3:
> * Addressed sathyanarayanan.kuppuswamy's review comments
>
> V2:
> * Rebased on top of the tree code
> * Addressed Bjorn's review comments
>
>  drivers/pci/pcie/aspm.c | 28 ++++++++++++++++++++++++++--
>  3 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index cfc5b84dc9c9..3db606ba9344 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1648,7 +1648,7 @@ static int pci_save_pcie_state(struct pci_dev *dev)
>  	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &cap[i++]);
>  	pcie_capability_read_word(dev, PCI_EXP_SLTCTL2, &cap[i++]);
>  
> -	pci_save_aspm_state(dev);
> +	pci_save_aspm_l1ss_state(dev);
>  	pci_save_ltr_state(dev);
>  
>  	return 0;
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index b217e74966eb..9fe78eb8b07d 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -95,7 +95,7 @@ void pci_msix_init(struct pci_dev *dev);
>  bool pci_bridge_d3_possible(struct pci_dev *dev);
>  void pci_bridge_d3_update(struct pci_dev *dev);
>  void pci_aspm_get_l1ss(struct pci_dev *pdev);
> -void pci_save_aspm_state(struct pci_dev *pdev);
> +void pci_save_aspm_l1ss_state(struct pci_dev *pdev);

is this rename a review request? It is not clear from the commit log
why you are doing it?

>  void pci_restore_aspm_state(struct pci_dev *pdev);
>  void pci_save_ltr_state(struct pci_dev *dev);
>  void pci_restore_ltr_state(struct pci_dev *dev);
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 7f1d674ff171..a62648dd52bc 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -24,13 +24,29 @@
>  
>  #include "../pci.h"
>  
> +static void pci_save_aspm_state(struct pci_dev *dev)
> +{
> +	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];
> +	pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[1]);
> +}
> +
>  void pci_aspm_get_l1ss(struct pci_dev *pdev)
>  {
>  	/* Read L1 PM substate capabilities */
>  	pdev->l1ss = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_L1SS);
>  }
>  
> -void pci_save_aspm_state(struct pci_dev *pdev)
> +void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
>  {
>  	struct pci_cap_saved_state *save_state;
>  	u16 l1ss = pdev->l1ss;
> @@ -309,10 +325,12 @@ static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
>  	struct pci_bus *linkbus = link->pdev->subordinate;
>  	u32 val = enable ? PCI_EXP_LNKCTL_CLKREQ_EN : 0;
>  
> -	list_for_each_entry(child, &linkbus->devices, bus_list)
> +	list_for_each_entry(child, &linkbus->devices, bus_list) {
>  		pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
>  						   PCI_EXP_LNKCTL_CLKREQ_EN,
>  						   val);
> +		pci_save_aspm_state(child);
> +	}
>  	link->clkpm_enabled = !!enable;
>  }
>  
> @@ -931,6 +949,12 @@ 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