linux-kernel - Re: [PATCH V3] PCI/ASPM: Update saved buffers with latest ASPM

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Date: Tue, 20 Feb 2024 09:37:14 +0530
From: Vidya Sagar <vidyas@...dia.com>
To: bhelgaas@...gle.com, macro@...am.me.uk, ajayagarwal@...gle.com,
 ilpo.jarvinen@...ux.intel.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
 hkallweit1@...il.com, michael.a.bottini@...ux.intel.com,
 johan+linaro@...nel.org
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 V3] PCI/ASPM: Update saved buffers with latest ASPM

Hi Bjorn,

Any comments for this patch?


Thanks,

Vidya Sagar


On 08-01-2024 18:12, 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 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.
>
> 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>
> ---
> 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 | 24 +++++++++++++++++++++++-
>   1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 67b13f26ba7c..1b4f03044ce2 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -138,16 +138,34 @@ static int policy_to_clkpm_state(struct pcie_link_state *link)
>   	return 0;
>   }
>   
> +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]);
> +}
> +
>   static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
>   {
>   	struct pci_dev *child;
>   	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;
>   }
>   
> @@ -767,6 +785,10 @@ 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_state(parent);
>   }
>   
>   static void pcie_config_aspm_path(struct pcie_link_state *link)