Re: [PATCH v7 06/12] PCI: Request control of native SHPC hotplug similarly to pciehp

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, May 17, 2018 at 12:28:57PM +0300, Mika Westerberg wrote:
> Now that the SHPC driver is converted to builtin we can change the way
> SHPC control is requested to follow more closely what we do for pciehp.
> We then take advantege of the newly introduced host->native_shpc_hotplug
> in acpi_get_hp_hw_control_from_firmware() to determine whether OSHP
> needs to be evaluated.
> 
> In addition provide two new functions that can be used to query whether
> native SHPC driver is expected to handle hotplug of a given bridge or
> not, following what we do for pciehp.
> 
> Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>  drivers/acpi/pci_root.c           |  4 ++++
>  drivers/pci/hotplug/acpi_pcihp.c  | 34 +++++++++++--------------------
>  drivers/pci/hotplug/shpchp.h      | 11 ----------
>  drivers/pci/hotplug/shpchp_core.c |  2 +-
>  drivers/pci/pci-acpi.c            | 21 +++++++++++++++++++
>  drivers/pci/probe.c               |  1 +
>  include/linux/pci.h               |  1 +
>  include/linux/pci_hotplug.h       | 15 +++++++++++++-
>  8 files changed, 54 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 02ab96f00952..da04502b4c0b 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -477,6 +477,8 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
>  
>  	if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
>  		control |= OSC_PCI_EXPRESS_NATIVE_HP_CONTROL;
> +	if (IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC))
> +		control |= OSC_PCI_SHPC_NATIVE_HP_CONTROL;
>  	if (pci_aer_available()) {
>  		if (aer_acpi_firmware_first())
>  			dev_info(&device->dev,
> @@ -903,6 +905,8 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>  	host_bridge = to_pci_host_bridge(bus->bridge);
>  	if (!(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
>  		host_bridge->native_pcie_hotplug = 0;
> +	if (!(root->osc_control_set & OSC_PCI_SHPC_NATIVE_HP_CONTROL))
> +		host_bridge->native_shpc_hotplug = 0;
>  	if (!(root->osc_control_set & OSC_PCI_EXPRESS_AER_CONTROL))
>  		host_bridge->native_aer = 0;
>  	if (!(root->osc_control_set & OSC_PCI_EXPRESS_PME_CONTROL))

This can be split into at least three patches.  I applied the above and
the connected pieces already.

> diff --git a/drivers/pci/hotplug/acpi_pcihp.c b/drivers/pci/hotplug/acpi_pcihp.c
> index c9816166978e..678c03944bb7 100644
> --- a/drivers/pci/hotplug/acpi_pcihp.c
> +++ b/drivers/pci/hotplug/acpi_pcihp.c
> @@ -62,23 +62,18 @@ static acpi_status acpi_run_oshp(acpi_handle handle)
>  
>  /**
>   * acpi_get_hp_hw_control_from_firmware
> - * @dev: the pci_dev of the bridge that has a hotplug controller
> - * @flags: requested control bits for _OSC
> + * @pdev: the pci_dev of the bridge that has a hotplug controller
>   *
>   * Attempt to take hotplug control from firmware.
>   */
> -int acpi_get_hp_hw_control_from_firmware(struct pci_dev *pdev, u32 flags)
> +int acpi_get_hp_hw_control_from_firmware(struct pci_dev *pdev)
>  {
> +	const struct pci_host_bridge *host;
> +	const struct acpi_pci_root *root;
>  	acpi_status status;
>  	acpi_handle chandle, handle;
>  	struct acpi_buffer string = { ACPI_ALLOCATE_BUFFER, NULL };
>  
> -	flags &= OSC_PCI_SHPC_NATIVE_HP_CONTROL;
> -	if (!flags) {
> -		err("Invalid flags %u specified!\n", flags);
> -		return -EINVAL;
> -	}

I also applied this trivial part (removal of the "flags" parameter).

>  	/*
>  	 * Per PCI firmware specification, we should run the ACPI _OSC
>  	 * method to get control of hotplug hardware before using it. If
> @@ -88,19 +83,14 @@ int acpi_get_hp_hw_control_from_firmware(struct pci_dev *pdev, u32 flags)
>  	 * OSHP within the scope of the hotplug controller and its parents,
>  	 * up to the host bridge under which this controller exists.
>  	 */
> -	handle = acpi_find_root_bridge_handle(pdev);
> -	if (handle) {
> -		acpi_get_name(handle, ACPI_FULL_PATHNAME, &string);
> -		dbg("Trying to get hotplug control for %s\n",
> -				(char *)string.pointer);
> -		status = acpi_pci_osc_control_set(handle, &flags, flags);
> -		if (ACPI_SUCCESS(status))
> -			goto got_one;
> -		if (status == AE_SUPPORT)
> -			goto no_control;
> -		kfree(string.pointer);
> -		string = (struct acpi_buffer){ ACPI_ALLOCATE_BUFFER, NULL };
> -	}
> +	host = pci_find_host_bridge(pdev->bus);
> +	if (host->native_shpc_hotplug)
> +		return 0;
> +
> +	/* If the there is _OSC we should not evaluate OSHP */
> +	root = acpi_pci_find_root(ACPI_HANDLE(&host->dev));
> +	if (root->osc_support_set)
> +		goto no_control;

And I applied this part as another separate patch.

>  	handle = ACPI_HANDLE(&pdev->dev);
>  	if (!handle) {
> diff --git a/drivers/pci/hotplug/shpchp.h b/drivers/pci/hotplug/shpchp.h
> index c55730b61c9a..9675ab757323 100644
> --- a/drivers/pci/hotplug/shpchp.h
> +++ b/drivers/pci/hotplug/shpchp.h
> @@ -173,17 +173,6 @@ static inline const char *slot_name(struct slot *slot)
>  	return hotplug_slot_name(slot->hotplug_slot);
>  }
>  
> -#ifdef CONFIG_ACPI
> -#include <linux/pci-acpi.h>
> -static inline int get_hp_hw_control_from_firmware(struct pci_dev *dev)
> -{
> -	u32 flags = OSC_PCI_SHPC_NATIVE_HP_CONTROL;
> -	return acpi_get_hp_hw_control_from_firmware(dev, flags);
> -}
> -#else
> -#define get_hp_hw_control_from_firmware(dev) (0)
> -#endif

I applied this piece as another separate patch.

>  struct ctrl_reg {
>  	volatile u32 base_offset;
>  	volatile u32 slot_avail1;
> diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c
> index 1f0f96908b5a..47decc9b3bb3 100644
> --- a/drivers/pci/hotplug/shpchp_core.c
> +++ b/drivers/pci/hotplug/shpchp_core.c
> @@ -277,7 +277,7 @@ static int is_shpc_capable(struct pci_dev *dev)
>  		return 1;
>  	if (!pci_find_capability(dev, PCI_CAP_ID_SHPC))
>  		return 0;
> -	if (get_hp_hw_control_from_firmware(dev))
> +	if (acpi_get_hp_hw_control_from_firmware(dev))
>  		return 0;
>  	return 1;
>  }
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 2fd96d008960..f3ed699108bf 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -394,6 +394,27 @@ bool pciehp_is_native(struct pci_dev *bridge)
>  	return host->native_pcie_hotplug;
>  }
>  
> +/**
> + * shpchp_is_native - Check whether a hotplug port is handled by the OS
> + * @bridge: Hotplug port to check
> + *
> + * Returns true if the given @bridge is handled by the native SHPC hotplug
> + * driver.
> + */
> +bool shpchp_is_native(struct pci_dev *bridge)
> +{
> +	const struct pci_host_bridge *host;
> +
> +	if (!IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC) || !bridge)
> +		return false;
> +
> +	if (!pci_find_capability(bridge, PCI_CAP_ID_SHPC))
> +		return false;
> +
> +	host = pci_find_host_bridge(bridge->bus);
> +	return host->native_shpc_hotplug;
> +}

This part needs to be reconciled somehow with is_shpc_capable() so
they give the same answer (and ideally use the same code instead of
duplicating it).

I pushed the current state of this to https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=pci/hotplug