Date:   Sat, 25 Jan 2020 15:25:00 -0800
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ashok.raj@...el.com, Keith Busch <keith.busch@...el.com>,
        Huong Nguyen <huong.nguyen@...l.com>,
        Austin Bolen <Austin.Bolen@...l.com>
Subject: Re: [PATCH v13 4/8] PCI/DPC: Add Error Disconnect Recover (EDR)
 support

On Fri, Jan 24, 2020 at 09:04:50AM -0600, Bjorn Helgaas wrote:
> On Sat, Jan 18, 2020 at 08:00:33PM -0800, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
> > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> > 
> > As per ACPI specification r6.3, sec 5.6.6, when firmware owns Downstream
> > Port Containment (DPC), its expected to use the "Error Disconnect
> > Recover" (EDR) notification to alert OSPM of a DPC event and if OS
> > supports EDR, its expected to handle the software state invalidation and
> > port recovery in OS, and also let firmware know the recovery status via
> > _OST ACPI call. Related _OST status codes can be found in ACPI
> > specification r6.3, sec 6.3.5.2.
> > 
> > Also, as per PCI firmware specification r3.2 Downstream Port Containment
> > Related Enhancements ECN, sec 4.5.1, table 4-6, If DPC is controlled by
> > firmware (firmware first mode), firmware is responsible for
> > configuring the DPC and OS is responsible for error recovery. Also, OS
> > is allowed to modify DPC registers only during the EDR notification
> > window. So with EDR support, OS should provide DPC port services even in
> > firmware first mode.
> > 
> > Cc: Keith Busch <keith.busch@...el.com>
> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> > Acked-by: Keith Busch <keith.busch@...el.com>
> > Tested-by: Huong Nguyen <huong.nguyen@...l.com>
> > Tested-by: Austin Bolen <Austin.Bolen@...l.com>
> > ---
> >  drivers/pci/pci-acpi.c   |  99 +++++++++++++++++++++++++++++++
> >  drivers/pci/pcie/Kconfig |  10 ++++
> >  drivers/pci/pcie/dpc.c   | 123 ++++++++++++++++++++++++++++++++++++++-
> >  include/linux/pci-acpi.h |  13 +++++
> >  4 files changed, 244 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> > index 0c02d500158f..920928f0d55c 100644
> > --- a/drivers/pci/pci-acpi.c
> > +++ b/drivers/pci/pci-acpi.c
> > @@ -103,6 +103,105 @@ int acpi_get_rc_resources(struct device *dev, const char *hid, u16 segment,
> >  }
> >  #endif
> >  
> > +#if defined(CONFIG_PCIE_DPC)
> > +
> > +/*
> > + * _DSM wrapper function to enable/disable DPC port.
> > + * @dpc   : DPC device structure
> > + * @enable: status of DPC port (0 or 1).
> > + *
> > + * returns 0 on success or errno on failure.
> > + */
> > +int acpi_enable_dpc_port(struct pci_dev *pdev, acpi_handle handle, bool enable)
> > +{
> > +	union acpi_object *obj, argv4, req;
> > +	int status = 0;
> > +
> > +	req.type = ACPI_TYPE_INTEGER;
> > +	req.integer.value = enable;
> > +
> > +	argv4.type = ACPI_TYPE_PACKAGE;
> > +	argv4.package.count = 1;
> > +	argv4.package.elements = &req;
> > +
> > +	/*
> > +	 * Per the Downstream Port Containment Related Enhancements ECN to
> > +	 * the PCI Firmware Specification r3.2, sec 4.6.12,
> > +	 * EDR_PORT_ENABLE_DSM is optional.  Return success if it's not
> > +	 * implemented.
> > +	 */
> > +	obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 5,
> > +				EDR_PORT_ENABLE_DSM, &argv4);
> > +	if (!obj)
> > +		return 0;
> > +
> > +	if (obj->type != ACPI_TYPE_INTEGER || obj->integer.value != enable)
> > +		status = -EIO;
> > +
> > +	ACPI_FREE(obj);
> > +
> > +	return status;
> > +}
> > +
> > +/*
> > + * _DSM wrapper function to locate DPC port.
> > + * @dpc   : DPC device structure
> > + *
> > + * returns pci_dev or NULL.
> > + */
> > +struct pci_dev *acpi_locate_dpc_port(struct pci_dev *pdev, acpi_handle handle)
> > +{
> > +	union acpi_object *obj;
> > +	u16 port;
> > +
> > +	obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 5,
> > +				EDR_PORT_LOCATE_DSM, NULL);
> > +	if (!obj)
> > +		return pci_dev_get(pdev);
> > +
> > +	if (obj->type != ACPI_TYPE_INTEGER) {
> > +		ACPI_FREE(obj);
> > +		return NULL;
> > +	}
> > +
> > +	/*
> > +	 * Firmware returns DPC port BDF details in following format:
> > +	 *	15:8 = bus
> > +	 *	 7:3 = device
> > +	 *	 2:0 = function
> > +	 */
> > +	port = obj->integer.value;
> > +
> > +	ACPI_FREE(obj);
> > +
> > +	return pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
> > +					   PCI_BUS_NUM(port), port & 0xff);
> > +}
> > +
> > +/*
> > + * _OST wrapper function to let firmware know the status of EDR event.
> > + * @dpc   : DPC device structure.
> > + * @status: Status of EDR event.
> > + */
> > +int acpi_send_edr_status(struct pci_dev *pdev, acpi_handle handle, u16 status)
> > +{
> > +	u32 ost_status;
> > +
> > +	pci_dbg(pdev, "Sending EDR status :%#x\n", status);
> > +
> > +	ost_status =  PCI_DEVID(pdev->bus->number, pdev->devfn);
> > +	ost_status = (ost_status << 16) | status;
> > +
> > +	status = acpi_evaluate_ost(handle,
> > +				   ACPI_NOTIFY_DISCONNECT_RECOVER,
> > +				   ost_status, NULL);
> > +	if (ACPI_FAILURE(status))
> > +		return -EINVAL;
> > +
> > +	return 0;
> > +}
> > +#endif /* CONFIG_PCIE_DPC */
> 
> I think we should try collecting all this stuff into a new pcie/edr.c
> file.  It could contain all the above, plus edr_handle_event() and
> maybe something like a "pci_acpi_add_edr_notifier()" that could be
> called from pci_acpi_setup() to install the notify handler.
> 
> I think the ACPI EDR stuff in dpc.c kind of clutters it up, especially
> for the non-ACPI systems that use dpc.c.
> 
> Obviously this would require some sort of interface exported from
> dpc.c to do the guts of edr_handle_event(), i.e., reading
> PCI_EXP_DPC_STATUS and calling dpc_process_error().
Ok. Let me move all EDR related code to edr.c. But, this might also 
require me to export a new interface similar to pcie_do_recovery
function. Since this function has dependency on port service
from which is its called, I might need to create a version without
this dependency.
> 
> >  phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
> >  {
> >  	acpi_status status = AE_NOT_EXIST;
> > diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
> > index 6e3c04b46fb1..772b1f4cb19e 100644
> > --- a/drivers/pci/pcie/Kconfig
> > +++ b/drivers/pci/pcie/Kconfig
> > @@ -140,3 +140,13 @@ config PCIE_BW
> >  	  This enables PCI Express Bandwidth Change Notification.  If
> >  	  you know link width or rate changes occur only to correct
> >  	  unreliable links, you may answer Y.
> > +
> > +config PCIE_EDR
> > +	bool "PCI Express Error Disconnect Recover support"
> > +	depends on PCIE_DPC && ACPI
> > +	help
> > +	  This option adds Error Disconnect Recover support as specified
> > +	  in the Downstream Port Containment Related Enhancements ECN to
> > +	  the PCI Firmware Specification r3.2.  Enable this if you want to
> > +	  support hybrid DPC model which uses both firmware and OS to
> > +	  implement DPC.
> > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> > index 9f58e91f8852..8a8ee374d9b1 100644
> > --- a/drivers/pci/pcie/dpc.c
> > +++ b/drivers/pci/pcie/dpc.c
> > @@ -13,6 +13,8 @@
> >  #include <linux/interrupt.h>
> >  #include <linux/init.h>
> >  #include <linux/pci.h>
> > +#include <linux/acpi.h>
> > +#include <linux/pci-acpi.h>
> >  
> >  #include "portdrv.h"
> >  #include "../pci.h"
> > @@ -23,6 +25,11 @@ struct dpc_dev {
> >  	bool			rp_extensions;
> >  	u8			rp_log_size;
> >  	bool			edr_enabled; /* EDR mode is supported */
> > +	pci_ers_result_t	error_state;
> > +	struct mutex		edr_lock;
> > +#ifdef CONFIG_ACPI
> > +	struct acpi_device	*adev;
> > +#endif
> >  };
> >  
> >  static const char * const rp_pio_error_string[] = {
> > @@ -161,6 +168,9 @@ static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
> >  	if (!pcie_wait_for_link(pdev, true))
> >  		return PCI_ERS_RESULT_DISCONNECT;
> >  
> > +	/* Since the device recovery is done just update the error state */
> > +	dpc->error_state = PCI_ERS_RESULT_RECOVERED;
> > +
> >  	return PCI_ERS_RESULT_RECOVERED;
> >  }
> >  
> > @@ -305,14 +315,94 @@ static irqreturn_t dpc_irq(int irq, void *context)
> >  	return IRQ_HANDLED;
> >  }
> >  
> > +static void dpc_error_resume(struct pci_dev *dev)
> > +{
> > +	struct dpc_dev *dpc = to_dpc_dev(dev);
> > +
> > +	dpc->error_state = PCI_ERS_RESULT_RECOVERED;
> > +}
> > +
> > +#ifdef CONFIG_ACPI
> > +
> > +static void edr_handle_event(acpi_handle handle, u32 event, void *data)
> > +{
> > +	struct dpc_dev *dpc = data;
> > +	struct pci_dev *pdev = dpc->dev->port;
> > +	u16 status;
> > +
> > +	pci_info(pdev, "ACPI event %#x received\n", event);
> > +
> > +	if (event != ACPI_NOTIFY_DISCONNECT_RECOVER)
> > +		return;
> > +
> > +	/*
> > +	 * Check if _DSM(0xD) is available, and if present locate the
> > +	 * port which issued EDR event.
> > +	 */
> > +	pdev = acpi_locate_dpc_port(pdev, dpc->adev->handle);
> > +	if (!pdev) {
> > +		pdev = dpc->dev->port;
> > +		pci_err(pdev, "No valid port found\n");
> 
i> This message should include the bus/device/function that we looked for.
Ok. I will add this in next version.
> 
> > +		return;
> > +	}
> > +
> > +	dpc = to_dpc_dev(pdev);
> > +	if (!dpc) {
> > +		pci_err(pdev, "DPC port is NULL\n");
> > +		goto done;
> > +	}
> > +
> > +	mutex_lock(&dpc->edr_lock);
> > +
> > +	dpc->error_state = PCI_ERS_RESULT_DISCONNECT;
> > +
> > +	/*
> > +	 * Check if the port supports DPC:
> > +	 *
> > +	 * If port supports DPC, then fall back to default error
> > +	 * recovery.
> > +	 */
> > +	if (dpc->cap_pos) {
> > +		/* Check if there is a valid DPC trigger */
> > +		pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_STATUS,
> > +				     &status);
> > +		if ((status & PCI_EXP_DPC_STATUS_TRIGGER))
> > +			dpc_process_error(dpc);
> > +		else
> > +			pci_err(pdev, "Invalid DPC trigger %#010x\n", status);
> > +	}
> > +
> > +	/*
> > +	 * If recovery is successful, send _OST(0xF, BDF << 16 | 0x80)
> > +	 * to firmware. If not successful, send _OST(0xF, BDF << 16 | 0x81).
> > +	 */
> > +	if (dpc->error_state == PCI_ERS_RESULT_RECOVERED)
> > +		status = EDR_OST_SUCCESS;
> > +	else
> > +		status = EDR_OST_FAILED;
> > +
> > +	/* Use ACPI handle of DPC event device for sending EDR status */
> > +	dpc = data;
> > +
> > +	acpi_send_edr_status(pdev, dpc->adev->handle, status);
> > +
> > +	mutex_unlock(&dpc->edr_lock);
> > +done:
> > +	pci_dev_put(pdev);
> > +}
> > +#endif
> > +
> >  #define FLAG(x, y) (((x) & (y)) ? '+' : '-')
> >  static int dpc_probe(struct pcie_device *dev)
> >  {
> >  	struct dpc_dev *dpc;
> >  	struct pci_dev *pdev = dev->port;
> >  	struct device *device = &dev->device;
> > -	int status;
> > +	int status = 0;
> >  	u16 ctl, cap;
> > +#ifdef CONFIG_ACPI
> > +	struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
> > +#endif
> >  
> >  	dpc = devm_kzalloc(device, sizeof(*dpc), GFP_KERNEL);
> >  	if (!dpc)
> > @@ -321,6 +411,9 @@ static int dpc_probe(struct pcie_device *dev)
> >  	dpc->cap_pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DPC);
> >  	dpc->dev = dev;
> >  
> > +	dpc->error_state = PCI_ERS_RESULT_NONE;
> > +	mutex_init(&dpc->edr_lock);
> > +
> >  	/*
> >  	 * As per PCIe r5.0, sec 6.2.10, implementation note titled
> >  	 * "Determination of DPC Control", to avoid conflicts over whether
> > @@ -358,6 +451,33 @@ static int dpc_probe(struct pcie_device *dev)
> >  		}
> >  	}
> >  
> > +#ifdef CONFIG_ACPI
> > +	if (pcie_aer_get_firmware_first(pdev) && adev) {
> 
> I'm not convinced about using pcie_aer_get_firmware_first() here yet.
> AFAICT the spec doesn't actually say anything like this (I'm looking
> at the ECN sec 4.5.1 description of "Error Disconnect Recover
> Supported".
If we are moving all EDR related code to edr.c, we will not need this
change.
> 
> > +		acpi_status astatus;
> > +
> > +		dpc->adev = adev;
> > +
> > +		astatus = acpi_install_notify_handler(adev->handle,
> > +						      ACPI_SYSTEM_NOTIFY,
> > +						      edr_handle_event,
> > +						      dpc);
> 
> I think there are a couple issues with the ECN here:
> 
>   - The ECN allows EDR notifications on host bridges (sec 4.5.1, table
>     4-4), but it does not allow the "Locate" _DSM under host bridges
>     (sec 4.6.13).
> 
>   - The ECN allows EDR notifications on root ports or switch ports
>     that do not support DPC (sec 4.5.1), but it does not allow the
>     "Locate" _DSM on those ports (sec 4.6.13).

Can you please give more details on where its mentioned? Following is
the copy of "Locate" _DSM location related specification. All it says is,
this object can be placed under any object representing root port or
switch port. It does not seem to add any restrictions. Please let me  know
your comments.

Location:
This object can be placed under any object representing a DPC capable
PCI Express Root Port or Switch Downstream Port. If a port implements
this DSM, its child devices cannot instantiate this DSM function

> 
> > +		if (ACPI_FAILURE(astatus)) {
> > +			pci_err(pdev,
> > +				"Install ACPI_SYSTEM_NOTIFY handler failed\n");
> > +			return -EBUSY;
> > +		}
> > +
> > +		status = acpi_enable_dpc_port(pdev, adev->handle, true);
> > +		if (status) {
> > +			pci_warn(pdev, "Enable DPC port failed\n");
> > +			acpi_remove_notify_handler(adev->handle,
> > +						   ACPI_SYSTEM_NOTIFY,
> > +						   edr_handle_event);
> > +			return status;
> > +		}
> > +	}
> > +#endif
> >  	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CAP, &cap);
> >  	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, &ctl);
> >  
> > @@ -409,6 +529,7 @@ static struct pcie_port_service_driver dpcdriver = {
> >  	.probe		= dpc_probe,
> >  	.remove		= dpc_remove,
> >  	.reset_link	= dpc_reset_link,
> > +	.error_resume   = dpc_error_resume,
> >  };
> >  
> >  int __init pcie_dpc_init(void)
> > diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
> > index 62b7fdcc661c..f4e0d5d984b0 100644
> > --- a/include/linux/pci-acpi.h
> > +++ b/include/linux/pci-acpi.h
> > @@ -111,6 +111,19 @@ extern const guid_t pci_acpi_dsm_guid;
> >  #define DEVICE_LABEL_DSM		0x07
> >  #define RESET_DELAY_DSM			0x08
> >  #define FUNCTION_DELAY_DSM		0x09
> > +#ifdef CONFIG_PCIE_DPC
> > +#define EDR_PORT_ENABLE_DSM		0x0C
> > +#define EDR_PORT_LOCATE_DSM		0x0D
> > +#define EDR_OST_SUCCESS			0x80
> > +#define EDR_OST_FAILED			0x81
> > +
> > +int acpi_enable_dpc_port(struct pci_dev *pdev, acpi_handle handle,
> > +			 bool enable);
> > +struct pci_dev *acpi_locate_dpc_port(struct pci_dev *pdev,
> > +				     acpi_handle handle);
> > +int acpi_send_edr_status(struct pci_dev *pdev,
> > +			 acpi_handle handle, u16 status);
> > +#endif /* CONFIG_PCIE_DPC */
> >  
> >  #else	/* CONFIG_ACPI */
> >  static inline void acpi_pci_add_bus(struct pci_bus *bus) { }
> > -- 
> > 2.21.0
> > 

-- 
Sathyanarayanan Kuppuswamy
Linux kernel developer

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