drivers/gpu/drm/xe/xe_device_sysfs.c

// SPDX-License-Identifier: MIT
/*
 * Copyright © 2023 Intel Corporation
 */

#include <linux/device.h>
#include <linux/kobject.h>
#include <linux/pci.h>
#include <linux/sysfs.h>

#include "xe_device.h"
#include "xe_device_sysfs.h"
#include "xe_mmio.h"
#include "xe_pcode_api.h"
#include "xe_pcode.h"
#include "xe_pm.h"

/**
 * DOC: Xe device sysfs
 * Xe driver requires exposing certain tunable knobs controlled by user space for
 * each graphics device. Considering this, we need to add sysfs attributes at device
 * level granularity.
 * These sysfs attributes will be available under pci device kobj directory.
 *
 * vram_d3cold_threshold - Report/change vram used threshold(in MB) below
 * which vram save/restore is permissible during runtime D3cold entry/exit.
 */

static ssize_t
vram_d3cold_threshold_show(struct device *dev,
			   struct device_attribute *attr, char *buf)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	struct xe_device *xe = pdev_to_xe_device(pdev);
	int ret;

	xe_pm_runtime_get(xe);
	ret = sysfs_emit(buf, "%d\n", xe->d3cold.vram_threshold);
	xe_pm_runtime_put(xe);

	return ret;
}

static ssize_t
vram_d3cold_threshold_store(struct device *dev, struct device_attribute *attr,
			    const char *buff, size_t count)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	struct xe_device *xe = pdev_to_xe_device(pdev);
	u32 vram_d3cold_threshold;
	int ret;

	ret = kstrtou32(buff, 0, &vram_d3cold_threshold);
	if (ret)
		return ret;

	drm_dbg(&xe->drm, "vram_d3cold_threshold: %u\n", vram_d3cold_threshold);

	xe_pm_runtime_get(xe);
	ret = xe_pm_set_vram_threshold(xe, vram_d3cold_threshold);
	xe_pm_runtime_put(xe);

	return ret ?: count;
}

static DEVICE_ATTR_RW(vram_d3cold_threshold);

/**
 * DOC: PCIe Gen5 Limitations
 *
 * Default link speed of discrete GPUs is determined by configuration parameters
 * stored in their flash memory, which are subject to override through user
 * initiated firmware updates. It has been observed that devices configured with
 * PCIe Gen5 as their default link speed can come across link quality issues due
 * to host or motherboard limitations and may have to auto-downgrade their link
 * to PCIe Gen4 speed when faced with unstable link at Gen5, which makes
 * firmware updates rather risky on such setups. It is required to ensure that
 * the device is capable of auto-downgrading its link to PCIe Gen4 speed before
 * pushing the firmware image with PCIe Gen5 as default configuration. This can
 * be done by reading ``auto_link_downgrade_capable`` sysfs entry, which will
 * denote if the device is capable of auto-downgrading its link to PCIe Gen4
 * speed with boolean output value of ``0`` or ``1``, meaning `incapable` or
 * `capable` respectively.
 *
 * .. code-block:: shell
 *
 *    $ cat /sys/bus/pci/devices/<bdf>/auto_link_downgrade_capable
 *
 * Pushing the firmware image with PCIe Gen5 as default configuration on a auto
 * link downgrade incapable device and facing link instability due to host or
 * motherboard limitations can result in driver failing to bind to the device,
 * making further firmware updates impossible with RMA being the only last
 * resort.
 *
 * Link downgrade status of auto link downgrade capable devices is available
 * through ``auto_link_downgrade_status`` sysfs entry with boolean output value
 * of ``0`` or ``1``, where ``0`` means no auto-downgrading was required during
 * link training (which is the optimal scenario) and ``1`` means the device has
 * auto-downgraded its link to PCIe Gen4 speed due to unstable Gen5 link.
 *
 * .. code-block:: shell
 *
 *    $ cat /sys/bus/pci/devices/<bdf>/auto_link_downgrade_status
 */

static ssize_t
auto_link_downgrade_capable_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	struct xe_device *xe = pdev_to_xe_device(pdev);
	u32 cap, val;

	xe_pm_runtime_get(xe);
	val = xe_mmio_read32(xe_root_tile_mmio(xe), BMG_PCIE_CAP);
	xe_pm_runtime_put(xe);

	cap = REG_FIELD_GET(LINK_DOWNGRADE, val);
	return sysfs_emit(buf, "%u\n", cap == DOWNGRADE_CAPABLE);
}
static DEVICE_ATTR_ADMIN_RO(auto_link_downgrade_capable);

static ssize_t
auto_link_downgrade_status_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	struct xe_device *xe = pdev_to_xe_device(pdev);
	/* default the auto_link_downgrade status to 0 */
	u32 val = 0;
	int ret;

	xe_pm_runtime_get(xe);
	ret = xe_pcode_read(xe_device_get_root_tile(xe),
			    PCODE_MBOX(DGFX_PCODE_STATUS, DGFX_GET_INIT_STATUS, 0),
			    &val, NULL);
	xe_pm_runtime_put(xe);

	return ret ?: sysfs_emit(buf, "%u\n", REG_FIELD_GET(DGFX_LINK_DOWNGRADE_STATUS, val));
}
static DEVICE_ATTR_ADMIN_RO(auto_link_downgrade_status);

static const struct attribute *auto_link_downgrade_attrs[] = {
	&dev_attr_auto_link_downgrade_capable.attr,
	&dev_attr_auto_link_downgrade_status.attr,
	NULL
};

static void xe_device_sysfs_fini(void *arg)
{
	struct xe_device *xe = arg;

	if (xe->d3cold.capable)
		sysfs_remove_file(&xe->drm.dev->kobj, &dev_attr_vram_d3cold_threshold.attr);

	if (xe->info.platform == XE_BATTLEMAGE)
		sysfs_remove_files(&xe->drm.dev->kobj, auto_link_downgrade_attrs);
}

int xe_device_sysfs_init(struct xe_device *xe)
{
	struct device *dev = xe->drm.dev;
	int ret;

	if (xe->d3cold.capable) {
		ret = sysfs_create_file(&dev->kobj, &dev_attr_vram_d3cold_threshold.attr);
		if (ret)
			return ret;
	}

	if (xe->info.platform == XE_BATTLEMAGE && !IS_SRIOV_VF(xe)) {
		ret = sysfs_create_files(&dev->kobj, auto_link_downgrade_attrs);
		if (ret)
			return ret;
	}

	return devm_add_action_or_reset(dev, xe_device_sysfs_fini, xe);
}