path: root/drivers/cxl/core/hdm.c

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright(c) 2022 Intel Corporation. All rights reserved. */
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/delay.h>

#include "cxlmem.h"
#include "core.h"

/**
 * DOC: cxl core hdm
 *
 * Compute Express Link Host Managed Device Memory, starting with the
 * CXL 2.0 specification, is managed by an array of HDM Decoder register
 * instances per CXL port and per CXL endpoint. Define common helpers
 * for enumerating these registers and capabilities.
 */

DECLARE_RWSEM(cxl_dpa_rwsem);

static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
			   int *target_map)
{
	int rc;

	rc = cxl_decoder_add_locked(cxld, target_map);
	if (rc) {
		put_device(&cxld->dev);
		dev_err(&port->dev, "Failed to add decoder\n");
		return rc;
	}

	rc = cxl_decoder_autoremove(&port->dev, cxld);
	if (rc)
		return rc;

	dev_dbg(&cxld->dev, "Added to port %s\n", dev_name(&port->dev));

	return 0;
}

/*
 * Per the CXL specification (8.2.5.12 CXL HDM Decoder Capability Structure)
 * single ported host-bridges need not publish a decoder capability when a
 * passthrough decode can be assumed, i.e. all transactions that the uport sees
 * are claimed and passed to the single dport. Disable the range until the first
 * CXL region is enumerated / activated.
 */
int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
{
	struct cxl_switch_decoder *cxlsd;
	struct cxl_dport *dport = NULL;
	int single_port_map[1];
	unsigned long index;

	cxlsd = cxl_switch_decoder_alloc(port, 1);
	if (IS_ERR(cxlsd))
		return PTR_ERR(cxlsd);

	device_lock_assert(&port->dev);

	xa_for_each(&port->dports, index, dport)
		break;
	single_port_map[0] = dport->port_id;

	return add_hdm_decoder(port, &cxlsd->cxld, single_port_map);
}
EXPORT_SYMBOL_NS_GPL(devm_cxl_add_passthrough_decoder, CXL);

static void parse_hdm_decoder_caps(struct cxl_hdm *cxlhdm)
{
	u32 hdm_cap;

	hdm_cap = readl(cxlhdm->regs.hdm_decoder + CXL_HDM_DECODER_CAP_OFFSET);
	cxlhdm->decoder_count = cxl_hdm_decoder_count(hdm_cap);
	cxlhdm->target_count =
		FIELD_GET(CXL_HDM_DECODER_TARGET_COUNT_MASK, hdm_cap);
	if (FIELD_GET(CXL_HDM_DECODER_INTERLEAVE_11_8, hdm_cap))
		cxlhdm->interleave_mask |= GENMASK(11, 8);
	if (FIELD_GET(CXL_HDM_DECODER_INTERLEAVE_14_12, hdm_cap))
		cxlhdm->interleave_mask |= GENMASK(14, 12);
}

static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
{
	struct cxl_hdm *cxlhdm;
	void __iomem *hdm;
	u32 ctrl;
	int i;

	if (!info)
		return false;

	cxlhdm = dev_get_drvdata(&info->port->dev);
	hdm = cxlhdm->regs.hdm_decoder;

	if (!hdm)
		return true;

	/*
	 * If HDM decoders are present and the driver is in control of
	 * Mem_Enable skip DVSEC based emulation
	 */
	if (!info->mem_enabled)
		return false;

	/*
	 * If any decoders are committed already, there should not be any
	 * emulated DVSEC decoders.
	 */
	for (i = 0; i < cxlhdm->decoder_count; i++) {
		ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(i));
		dev_dbg(&info->port->dev,
			"decoder%d.%d: committed: %ld base: %#x_%.8x size: %#x_%.8x\n",
			info->port->id, i,
			FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl),
			readl(hdm + CXL_HDM_DECODER0_BASE_HIGH_OFFSET(i)),
			readl(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(i)),
			readl(hdm + CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(i)),
			readl(hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(i)));
		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
			return false;
	}

	return true;
}

/**
 * devm_cxl_setup_hdm - map HDM decoder component registers
 * @port: cxl_port to map
 * @info: cached DVSEC range register info
 */
struct cxl_hdm *devm_cxl_setup_hdm(struct cxl_port *port,
				   struct cxl_endpoint_dvsec_info *info)
{
	struct cxl_register_map *reg_map = &port->reg_map;
	struct device *dev = &port->dev;
	struct cxl_hdm *cxlhdm;
	int rc;

	cxlhdm = devm_kzalloc(dev, sizeof(*cxlhdm), GFP_KERNEL);
	if (!cxlhdm)
		return ERR_PTR(-ENOMEM);
	cxlhdm->port = port;
	dev_set_drvdata(dev, cxlhdm);

	/* Memory devices can configure device HDM using DVSEC range regs. */
	if (reg_map->resource == CXL_RESOURCE_NONE) {
		if (!info || !info->mem_enabled) {
			dev_err(dev, "No component registers mapped\n");
			return ERR_PTR(-ENXIO);
		}

		cxlhdm->decoder_count = info->ranges;
		return cxlhdm;
	}

	if (!reg_map->component_map.hdm_decoder.valid) {
		dev_dbg(&port->dev, "HDM decoder registers not implemented\n");
		/* unique error code to indicate no HDM decoder capability */
		return ERR_PTR(-ENODEV);
	}

	rc = cxl_map_component_regs(reg_map, &cxlhdm->regs,
				    BIT(CXL_CM_CAP_CAP_ID_HDM));
	if (rc) {
		dev_err(dev, "Failed to map HDM capability.\n");
		return ERR_PTR(rc);
	}

	parse_hdm_decoder_caps(cxlhdm);
	if (cxlhdm->decoder_count == 0) {
		dev_err(dev, "Spec violation. Caps invalid\n");
		return ERR_PTR(-ENXIO);
	}

	/*
	 * Now that the hdm capability is parsed, decide if range
	 * register emulation is needed and fix