[PATCH v1 05/14] xen/arm: PCI host bridge discovery within XEN on ARM

[Rahul Singh <rahul.singh@xxxxxxx>]

XEN during boot will read the PCI device tree node “reg” property
and will map the PCI config space to the XEN memory.

As of now "pci-host-ecam-generic" compatible board is supported.

"linux,pci-domain" device tree property assigns a fixed PCI domain
number to a host bridge, otherwise an unstable (across boots) unique
number will be assigned by Linux.This property has to be in sync with
XEN to access the PCI devices.

XEN will read the “linux,pci-domain” property from the device tree node
and configure the host bridge segment number accordingly. If this
property is not available XEN will allocate the unique segment number
to the host bridge.

dt_get_pci_domain_nr(..) and dt_pci_bus_find_domain_nr(..) are directly
imported from the Linux source tree.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
 xen/arch/arm/pci/Makefile           |   2 +
 xen/arch/arm/pci/pci-host-common.c  | 261 ++++++++++++++++++++++++++++
 xen/arch/arm/pci/pci-host-generic.c |  55 ++++++
 xen/include/asm-arm/pci.h           |  28 +++
 4 files changed, 346 insertions(+)
 create mode 100644 xen/arch/arm/pci/pci-host-common.c
 create mode 100644 xen/arch/arm/pci/pci-host-generic.c

diff --git a/xen/arch/arm/pci/Makefile b/xen/arch/arm/pci/Makefile
index a9ee0b9b44..f3d97f859e 100644
--- a/xen/arch/arm/pci/Makefile
+++ b/xen/arch/arm/pci/Makefile
@@ -1,2 +1,4 @@
 obj-y += pci.o
 obj-y += pci-access.o
+obj-y += pci-host-generic.o
+obj-y += pci-host-common.o
diff --git a/xen/arch/arm/pci/pci-host-common.c 
b/xen/arch/arm/pci/pci-host-common.c
new file mode 100644
index 0000000000..9dd9b02271
--- /dev/null
+++ b/xen/arch/arm/pci/pci-host-common.c
@@ -0,0 +1,261 @@
+/*
+ * Copyright (C) 2021 Arm Ltd.
+ *
+ * Based on Linux drivers/pci/ecam.c
+ * Copyright 2016 Broadcom.
+ *
+ * Based on Linux drivers/pci/controller/pci-host-common.c
+ * Based on Linux drivers/pci/controller/pci-host-generic.c
+ * Copyright (C) 2014 ARM Limited Will Deacon <will.deacon@xxxxxxx>
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <xen/init.h>
+#include <xen/pci.h>
+#include <asm/pci.h>
+#include <xen/rwlock.h>
+#include <xen/sched.h>
+#include <xen/vmap.h>
+
+/*
+ * List for all the pci host bridges.
+ */
+
+static LIST_HEAD(pci_host_bridges);
+
+static atomic_t domain_nr = ATOMIC_INIT(-1);
+
+bool dt_pci_parse_bus_range(struct dt_device_node *dev,
+                            struct pci_config_window *cfg)
+{
+    const __be32 *cells;
+    uint32_t len;
+
+    cells = dt_get_property(dev, "bus-range", &len);
+    /* bus-range should at least be 2 cells */
+    if ( !cells || (len < (sizeof(*cells) * 2)) )
+        return false;
+
+    cfg->busn_start = dt_next_cell(1, &cells);
+    cfg->busn_end = dt_next_cell(1, &cells);
+
+    return true;
+}
+
+static inline void __iomem *pci_remap_cfgspace(paddr_t start, size_t len)
+{
+    return ioremap_nocache(start, len);
+}
+
+static void pci_ecam_free(struct pci_config_window *cfg)
+{
+    if ( cfg->win )
+        iounmap(cfg->win);
+
+    xfree(cfg);
+}
+
+static struct pci_config_window *gen_pci_init(struct dt_device_node *dev,
+                                              int ecam_reg_idx)
+{
+    int err;
+    struct pci_config_window *cfg;
+    paddr_t addr, size;
+
+    cfg = xzalloc(struct pci_config_window);
+    if ( !cfg )
+        return NULL;
+
+    err = dt_pci_parse_bus_range(dev, cfg);
+    if ( !err ) {
+        cfg->busn_start = 0;
+        cfg->busn_end = 0xff;
+        printk(XENLOG_ERR "%s:No bus range found for pci controller\n",
+               dt_node_full_name(dev));
+    } else {
+        if ( cfg->busn_end > cfg->busn_start + 0xff )
+            cfg->busn_end = cfg->busn_start + 0xff;
+    }
+
+    /* Parse our PCI ecam register address*/
+    err = dt_device_get_address(dev, ecam_reg_idx, &addr, &size);
+    if ( err )
+        goto err_exit;
+
+    cfg->phys_addr = addr;
+    cfg->size = size;
+
+    /*
+     * On 64-bit systems, we do a single ioremap for the whole config space
+     * since we have enough virtual address range available.  On 32-bit, we
+     * ioremap the config space for each bus individually.
+     *
+     * As of now only 64-bit is supported 32-bit is not supported.
+     */
+    cfg->win = pci_remap_cfgspace(cfg->phys_addr, cfg->size);
+    if ( !cfg->win )
+        goto err_exit_remap;
+
+    printk("ECAM at [mem %lx-%lx] for [bus %x-%x] \n",cfg->phys_addr,
+            cfg->phys_addr + cfg->size - 1, cfg->busn_start, cfg->busn_end);
+
+    return cfg;
+
+err_exit_remap:
+    printk(XENLOG_ERR "ECAM ioremap failed\n");
+err_exit:
+    pci_ecam_free(cfg);
+    return NULL;
+}
+
+struct pci_host_bridge *pci_alloc_host_bridge(void)
+{
+    struct pci_host_bridge *bridge = xzalloc(struct pci_host_bridge);
+
+    if ( !bridge )
+        return NULL;
+
+    INIT_LIST_HEAD(&bridge->node);
+    bridge->bus_start = ~0;
+    bridge->bus_end = ~0;
+    return bridge;
+}
+
+void pci_add_host_bridge(struct pci_host_bridge *bridge)
+{
+    list_add_tail(&bridge->node, &pci_host_bridges);
+}
+
+static int pci_get_new_domain_nr(void)
+{
+    return atomic_inc_return(&domain_nr);
+}
+
+/*
+ * This function will try to obtain the host bridge domain number by
+ * finding a property called "linux,pci-domain" of the given device node.
+ *
+ * @node: device tree node with the domain information
+ *
+ * Returns the associated domain number from DT in the range [0-0xffff], or
+ * a negative value if the required property is not found.
+ */
+static int dt_get_pci_domain_nr(struct dt_device_node *node)
+{
+    u32 domain;
+    int error;
+
+    error = dt_property_read_u32(node, "linux,pci-domain", &domain);
+    if ( !error )
+        return -EINVAL;
+
+    return (u16)domain;
+}
+
+static int pci_bus_find_domain_nr(struct dt_device_node *dev)
+{
+    static int use_dt_domains = -1;
+    int domain;
+
+    domain = dt_get_pci_domain_nr(dev);
+
+    /*
+     * Check DT domain and use_dt_domains values.
+     *
+     * If DT domain property is valid (domain >= 0) and
+     * use_dt_domains != 0, the DT assignment is valid since this means
+     * we have not previously allocated a domain number by using
+     * pci_get_new_domain_nr(); we should also update use_dt_domains to
+     * 1, to indicate that we have just assigned a domain number from
+     * DT.
+     *
+     * If DT domain property value is not valid (ie domain < 0), and we
+     * have not previously assigned a domain number from DT
+     * (use_dt_domains != 1) we should assign a domain number by
+     * using the:
+     *
+     * pci_get_new_domain_nr()
+     *
+     * API and update the use_dt_domains value to keep track of method we
+     * are using to assign domain numbers (use_dt_domains = 0).
+     *
+     * All other combinations imply we have a platform that is trying
+     * to mix domain numbers obtained from DT and pci_get_new_domain_nr(),
+     * which is a recipe for domain mishandling and it is prevented by
+     * invalidating the domain value (domain = -1) and printing a
+     * corresponding error.
+     */
+    if ( domain >= 0 && use_dt_domains )
+    {
+        use_dt_domains = 1;
+    }
+    else if ( domain < 0 && use_dt_domains != 1 )
+    {
+        use_dt_domains = 0;
+        domain = pci_get_new_domain_nr();
+    }
+    else
+    {
+        printk(XENLOG_ERR "Inconsistent \"linux,pci-domain\" property in 
DT\n");
+        BUG();
+    }
+
+    return domain;
+}
+
+int pci_host_common_probe(struct dt_device_node *dev,
+                          int ecam_reg_idx)
+{
+    struct pci_host_bridge *bridge;
+    struct pci_config_window *cfg;
+    int err;
+
+    bridge = pci_alloc_host_bridge();
+    if ( !bridge )
+        return -ENOMEM;
+
+    /* Parse and map our Configuration Space windows */
+    cfg = gen_pci_init(dev, ecam_reg_idx);
+    if ( !cfg )
+    {
+        err = -ENOMEM;
+        goto err_exit;
+    }
+
+    bridge->dt_node = dev;
+    bridge->sysdata = cfg;
+    bridge->bus_start = cfg->busn_start;
+    bridge->bus_end = cfg->busn_end;
+
+    bridge->segment = pci_bus_find_domain_nr(dev);
+
+    pci_add_host_bridge(bridge);
+
+    return 0;
+
+err_exit:
+    xfree(bridge);
+    return err;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/arm/pci/pci-host-generic.c 
b/xen/arch/arm/pci/pci-host-generic.c
new file mode 100644
index 0000000000..13d0f7f999
--- /dev/null
+++ b/xen/arch/arm/pci/pci-host-generic.c
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2021 Arm Ltd.
+ *
+ * Based on Linux drivers/pci/controller/pci-host-common.c
+ * Based on Linux drivers/pci/controller/pci-host-generic.c
+ * Copyright (C) 2014 ARM Limited Will Deacon <will.deacon@xxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <asm/device.h>
+#include <xen/pci.h>
+#include <asm/pci.h>
+
+static const struct dt_device_match gen_pci_dt_match[] = {
+    { .compatible = "pci-host-ecam-generic" },
+    { },
+};
+
+static int gen_pci_dt_init(struct dt_device_node *dev, const void *data)
+{
+    const struct dt_device_match *of_id;
+
+    of_id = dt_match_node(gen_pci_dt_match, dev->dev.of_node);
+
+    printk(XENLOG_INFO "Found PCI host bridge %s compatible:%s \n",
+           dt_node_full_name(dev), of_id->compatible);
+
+    return pci_host_common_probe(dev, 0);
+}
+
+DT_DEVICE_START(pci_gen, "PCI HOST GENERIC", DEVICE_PCI)
+.dt_match = gen_pci_dt_match,
+.init = gen_pci_dt_init,
+DT_DEVICE_END
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/asm-arm/pci.h b/xen/include/asm-arm/pci.h
index 61e43da088..58a51e724e 100644
--- a/xen/include/asm-arm/pci.h
+++ b/xen/include/asm-arm/pci.h
@@ -26,6 +26,34 @@ struct arch_pci_dev {
     struct device dev;
 };
 
+/*
+ * struct to hold the mappings of a config space window. This
+ * is expected to be used as sysdata for PCI controllers that
+ * use ECAM.
+ */
+struct pci_config_window {
+    paddr_t         phys_addr;
+    paddr_t         size;
+    uint8_t         busn_start;
+    uint8_t         busn_end;
+    void __iomem    *win;
+};
+
+/*
+ * struct to hold pci host bridge information
+ * for a PCI controller.
+ */
+struct pci_host_bridge {
+    struct dt_device_node *dt_node;  /* Pointer to the associated DT node */
+    struct list_head node;           /* Node in list of host bridges */
+    uint16_t segment;                /* Segment number */
+    u8 bus_start;                    /* Bus start of this bridge. */
+    u8 bus_end;                      /* Bus end of this bridge. */
+    void *sysdata;                   /* Pointer to the config space window*/
+};
+
+int pci_host_common_probe(struct dt_device_node *dev,
+                          int ecam_reg_idx);
 #else   /*!CONFIG_HAS_PCI*/
 
 struct arch_pci_dev { };
-- 
2.17.1