linux-kernel - Re: [PATCH 2/2] PCI: vmd: enable PCI PM's L1 substates of remapped PCIe port and NVMe

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Message-ID: <ZboF9oSWi5OAV_NJ@hovoldconsulting.com>
Date: Wed, 31 Jan 2024 09:33:58 +0100
From: Johan Hovold <johan@...nel.org>
To: Jian-Hong Pan <jhp@...lessos.org>
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>,
	David Box <david.e.box@...ux.intel.com>,
	Damien Le Moal <dlemoal@...nel.org>,
	Niklas Cassel <cassel@...nel.org>,
	Nirmal Patel <nirmal.patel@...ux.intel.com>,
	Jonathan Derrick <jonathan.derrick@...ux.dev>,
	linux-ide@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux@...lessos.org
Subject: Re: [PATCH 2/2] PCI: vmd: enable PCI PM's L1 substates of remapped
 PCIe port and NVMe

On Tue, Jan 30, 2024 at 06:00:51PM +0800, Jian-Hong Pan wrote:
> The remmapped PCIe port and NVMe have PCI PM L1 substates capability on
> ASUS B1400CEAE, but they are disabled originally:
> 
> Capabilities: [900 v1] L1 PM Substates
>         L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+
>                   PortCommonModeRestoreTime=32us PortTPowerOnTime=10us
>         L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1-
>                    T_CommonMode=0us LTR1.2_Threshold=0ns
>         L1SubCtl2: T_PwrOn=10us
> 
> Power on all of the VMD remapped PCI devices before enable PCI-PM L1 PM
> Substates by following "Section 5.5.4 of PCIe Base Spec Revision 5.0
> Version 0.1". Then, PCI PM's L1 substates control are enabled
> accordingly.
 
> +static int vmd_power_on_pci_device(struct pci_dev *pdev, void *userdata)
> +{
> +	pci_set_power_state(pdev, PCI_D0);

As I believe Bjorn already hinted at, this should probably be done in
vmd_pm_enable_quirk().

Also, you need to use the new pci_set_power_state_locked() helper since
these callbacks are called from pci_walk_bus() with the bus semaphore
held:

	https://lore.kernel.org/lkml/20240130100243.11011-1-johan+linaro@kernel.org/

> +	return 0;
> +}
> +
>  /*
>   * Enable ASPM and LTR settings on devices that aren't configured by BIOS.
>   */
> @@ -928,6 +934,13 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  	vmd_acpi_begin();
>  
>  	pci_scan_child_bus(vmd->bus);
> +
> +	/*
> +	 * Make PCI devices at D0 when enable PCI-PM L1 PM Substates from
> +	 * Section 5.5.4 of PCIe Base Spec Revision 5.0 Version 0.1
> +	 */
> +	pci_walk_bus(vmd->bus, vmd_power_on_pci_device, NULL);
> +
>  	vmd_domain_reset(vmd);
>  
>  	/* When Intel VMD is enabled, the OS does not discover the Root Ports

Johan