linux-kernel - Re: [PATCH v1 4/4] PCI/ACPI: Advertise HPX type 3 support via

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Date:   Tue, 23 Apr 2019 16:38:50 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Alexandru Gagniuc <mr.nuke.me@...il.com>
Cc:     austin_bolen@...l.com, alex_gagniuc@...lteam.com,
        keith.busch@...el.com, Shyam_Iyer@...l.com, lukas@...ner.de,
        okaya@...nel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/4] PCI/ACPI: Advertise HPX type 3 support via _OSC

On Fri, Mar 15, 2019 at 02:29:40PM -0500, Alexandru Gagniuc wrote:
> _OSC now has a way to inform firmware that OS has the capability to
> interpret HPX type 3 tables. Since ACPI 6.3 deprecated _OSC specifics,
> these are now part of the PCI Firmware Specification.
> 
> The following is the document describing the changes:
> ECN:	_HPX and PCIe Completion Timeout related _OSC Enhancements
> Date:	September 12, 2018
> Affected Document: PCI Firmware Specification, Rev. 3.2
> 
> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>

Applied to pci/hotplug for v5.2, thanks!

> ---
> 
> This patch is designed to go on top of the following series
> "PCI: ACPI: Implement support for _HPX Type 3 tables"
> 	https://lkml.org/lkml/2019/3/7/790
> 
> Although the patch can technically be applied independently, it
> doesn't make sense without the rest of the series.
> 
> The HPX3 capability bit, to my understanding, is designed to be
> informational. i.e. Setting or not setting it would not affect whether
> firmware would export HPX3 tables. It may have implications in FFS
> systems, where FW might need to make sure things like the completion
> timeout value is set correctly throughout the tree.
> 
> My understanding is that firmware will prefer to set these with HPX3,
> in lieu of firing up SMM on hotplug and other events. Firmware can use
> the HPX3 support bit to know how to proceed.
> 
>  drivers/acpi/pci_root.c | 2 ++
>  include/linux/acpi.h    | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 707aafc7c2aa..0bee23893297 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -145,6 +145,7 @@ static struct pci_osc_bit_struct pci_osc_support_bit[] = {
>  	{ OSC_PCI_CLOCK_PM_SUPPORT, "ClockPM" },
>  	{ OSC_PCI_SEGMENT_GROUPS_SUPPORT, "Segments" },
>  	{ OSC_PCI_MSI_SUPPORT, "MSI" },
> +	{ OSC_PCI_HPX_TYPE_3_SUPPORT, "HPX-type3" },
>  };
>  
>  static struct pci_osc_bit_struct pci_osc_control_bit[] = {
> @@ -446,6 +447,7 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
>  	 * PCI domains, so we indicate this in _OSC support capabilities.
>  	 */
>  	support = OSC_PCI_SEGMENT_GROUPS_SUPPORT;
> +	support |= OSC_PCI_HPX_TYPE_3_SUPPORT;
>  	if (pci_ext_cfg_avail())
>  		support |= OSC_PCI_EXT_CONFIG_SUPPORT;
>  	if (pcie_aspm_support_enabled())
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 87715f20b69a..028c138b9082 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -508,7 +508,8 @@ extern bool osc_pc_lpi_support_confirmed;
>  #define OSC_PCI_CLOCK_PM_SUPPORT		0x00000004
>  #define OSC_PCI_SEGMENT_GROUPS_SUPPORT		0x00000008
>  #define OSC_PCI_MSI_SUPPORT			0x00000010
> -#define OSC_PCI_SUPPORT_MASKS			0x0000001f
> +#define OSC_PCI_HPX_TYPE_3_SUPPORT		0x00000100
> +#define OSC_PCI_SUPPORT_MASKS			0x0000011f
>  
>  /* PCI Host Bridge _OSC: Capabilities DWORD 3: Control Field */
>  #define OSC_PCI_EXPRESS_NATIVE_HP_CONTROL	0x00000001
> -- 
> 2.19.2
>