Re: [RFC PATCH v1 1/4] arm/pci: PCI setup and PCI host bridge discovery within XEN on ARM.

[Rahul Singh <Rahul.Singh@xxxxxxx>]

> On 24 Jul 2020, at 8:03 am, Oleksandr Andrushchenko 
> <Oleksandr_Andrushchenko@xxxxxxxx> wrote:
> 
> 
> On 7/24/20 2:38 AM, Stefano Stabellini wrote:
>> + Jan, Andrew, Roger
>> 
>> Please have a look at my comment on whether we should share the MMCFG
>> code below, feel free to ignore the rest :-)
>> 
>> 
>> On Thu, 23 Jul 2020, Rahul Singh wrote:
>>> XEN during boot will read the PCI device tree node “reg” property
>>> and will map the PCI config space to the XEN memory.
>>> 
>>> XEN will read the “linux, pci-domain” property from the device tree
>>> node and configure the host bridge segment number accordingly.
>>> 
>>> As of now "pci-host-ecam-generic" compatible board is supported.
>>> 
>>> Change-Id: If32f7748b7dc89dd37114dc502943222a2a36c49
>> What is this Change-Id property?
> Gerrit ;)
>> 
>> 
>>> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
>>> ---
>>>  xen/arch/arm/Kconfig                |   7 +
>>>  xen/arch/arm/Makefile               |   1 +
>>>  xen/arch/arm/pci/Makefile           |   4 +
>>>  xen/arch/arm/pci/pci-access.c       | 101 ++++++++++++++
>>>  xen/arch/arm/pci/pci-host-common.c  | 198 ++++++++++++++++++++++++++++
>>>  xen/arch/arm/pci/pci-host-generic.c | 131 ++++++++++++++++++
>>>  xen/arch/arm/pci/pci.c              | 112 ++++++++++++++++
>>>  xen/arch/arm/setup.c                |   2 +
>>>  xen/include/asm-arm/device.h        |   7 +-
>>>  xen/include/asm-arm/pci.h           |  97 +++++++++++++-
>>>  10 files changed, 654 insertions(+), 6 deletions(-)
>>>  create mode 100644 xen/arch/arm/pci/Makefile
>>>  create mode 100644 xen/arch/arm/pci/pci-access.c
>>>  create mode 100644 xen/arch/arm/pci/pci-host-common.c
>>>  create mode 100644 xen/arch/arm/pci/pci-host-generic.c
>>>  create mode 100644 xen/arch/arm/pci/pci.c
>>> 
>>> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
>>> index 2777388265..ee13339ae9 100644
>>> --- a/xen/arch/arm/Kconfig
>>> +++ b/xen/arch/arm/Kconfig
>>> @@ -31,6 +31,13 @@ menu "Architecture Features"
>>> 
>>>  source "arch/Kconfig"
>>> 
>>> +config ARM_PCI
>>> +   bool "PCI Passthrough Support"
>>> +   depends on ARM_64
>>> +   ---help---
>>> +
>>> +     PCI passthrough support for Xen on ARM64.
>>> +
>>>  config ACPI
>>>     bool "ACPI (Advanced Configuration and Power Interface) Support" if 
>>> EXPERT
>>>     depends on ARM_64
>>> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
>>> index 7e82b2178c..345cb83eed 100644
>>> --- a/xen/arch/arm/Makefile
>>> +++ b/xen/arch/arm/Makefile
>>> @@ -6,6 +6,7 @@ ifneq ($(CONFIG_NO_PLAT),y)
>>>  obj-y += platforms/
>>>  endif
>>>  obj-$(CONFIG_TEE) += tee/
>>> +obj-$(CONFIG_ARM_PCI) += pci/
>>> 
>>>  obj-$(CONFIG_HAS_ALTERNATIVE) += alternative.o
>>>  obj-y += bootfdt.init.o
>>> diff --git a/xen/arch/arm/pci/Makefile b/xen/arch/arm/pci/Makefile
>>> new file mode 100644
>>> index 0000000000..358508b787
>>> --- /dev/null
>>> +++ b/xen/arch/arm/pci/Makefile
>>> @@ -0,0 +1,4 @@
>>> +obj-y += pci.o
>>> +obj-y += pci-host-generic.o
>>> +obj-y += pci-host-common.o
>>> +obj-y += pci-access.o
>>> diff --git a/xen/arch/arm/pci/pci-access.c b/xen/arch/arm/pci/pci-access.c
>>> new file mode 100644
>>> index 0000000000..c53ef58336
>>> --- /dev/null
>>> +++ b/xen/arch/arm/pci/pci-access.c
>>> @@ -0,0 +1,101 @@
>>> +/*
>>> + * Copyright (C) 2020 Arm Ltd.
> I think SPDX will fit better in any new code.

It will be good if community helps us to decide which license is best for new 
files.

>>> + *
>>> + * 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>
>>> +
>>> +static uint32_t pci_config_read(pci_sbdf_t sbdf, unsigned int reg,
>>> +                            unsigned int len)
>>> +{
>>> +    int rc;
>>> +    uint32_t val = GENMASK(0, len * 8);
>>> +
>>> +    struct pci_host_bridge *bridge = pci_find_host_bridge(sbdf.seg, 
>>> sbdf.bus);
>>> +
>>> +    if ( unlikely(!bridge) )
>>> +    {
>>> +        printk(XENLOG_ERR "Unable to find bridge for "PRI_pci"\n",
>>> +                sbdf.seg, sbdf.bus, sbdf.dev, sbdf.fn);
>>> +        return val;
>>> +    }
>>> +
>>> +    if ( unlikely(!bridge->ops->read) )
>>> +        return val;
>>> +
>>> +    rc = bridge->ops->read(bridge, (uint32_t) sbdf.sbdf, reg, len, &val);
>>> +    if ( rc )
>>> +        printk(XENLOG_ERR "Failed to read reg %#x len %u for "PRI_pci"\n",
>>> +                reg, len, sbdf.seg, sbdf.bus, sbdf.dev, sbdf.fn);
>>> +
>>> +    return val;
>>> +}
>>> +
>>> +static void pci_config_write(pci_sbdf_t sbdf, unsigned int reg,
>>> +        unsigned int len, uint32_t val)
>>> +{
>>> +    int rc;
>>> +    struct pci_host_bridge *bridge = pci_find_host_bridge(sbdf.seg, 
>>> sbdf.bus);
>>> +
>>> +    if ( unlikely(!bridge) )
>>> +    {
>>> +        printk(XENLOG_ERR "Unable to find bridge for "PRI_pci"\n",
>>> +                sbdf.seg, sbdf.bus, sbdf.dev, sbdf.fn);
>>> +        return;
>>> +    }
>>> +
>>> +    if ( unlikely(!bridge->ops->write) )
>>> +        return;
>>> +
>>> +    rc = bridge->ops->write(bridge, (uint32_t) sbdf.sbdf, reg, len, val);
>>> +    if ( rc )
>>> +        printk(XENLOG_ERR "Failed to write reg %#x len %u for "PRI_pci"\n",
>>> +                reg, len, sbdf.seg, sbdf.bus, sbdf.dev, sbdf.fn);
>>> +}
>>> +
>>> +/*
>>> + * Wrappers for all PCI configuration access functions.
>>> + */
>>> +
>>> +#define PCI_OP_WRITE(size, type) \
>>> +    void pci_conf_write##size (pci_sbdf_t sbdf,unsigned int reg, type val) 
>>> \
>>> +{                                               \
>>> +    pci_config_write(sbdf, reg, size / 8, val);     \
>>> +}
>>> +
>>> +#define PCI_OP_READ(size, type) \
>>> +    type pci_conf_read##size (pci_sbdf_t sbdf, unsigned int reg)  \
>>> +{                                               \
>>> +    return pci_config_read(sbdf, reg, size / 8);     \
>>> +}
>>> +
>>> +PCI_OP_READ(8, u8)
>>> +PCI_OP_READ(16, u16)
>>> +PCI_OP_READ(32, u32)
>>> +PCI_OP_WRITE(8, u8)
>>> +PCI_OP_WRITE(16, u16)
>>> +PCI_OP_WRITE(32, u32)
>> This looks like a subset of xen/arch/x86/x86_64/mmconfig_64.c ?
>> 
>> MMCFG is supposed to cover ECAM-compliant host bridges too, if I am not
>> mistaken. Is there any value in sharing the code with x86? It is OK if
>> we don't, but I would like to understand the reasoning.
>> 
>> 
>> 
>>> +/*
>>> + * 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-common.c 
>>> b/xen/arch/arm/pci/pci-host-common.c
>>> new file mode 100644
>>> index 0000000000..c5f98be698
>>> --- /dev/null
>>> +++ b/xen/arch/arm/pci/pci-host-common.c
>>> @@ -0,0 +1,198 @@
>>> +/*
>>> + * Copyright (C) 2020 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/vmap.h>
>>> +
>>> +/*
>>> + * List for all the pci host bridges.
>>> + */
>>> +
>>> +static LIST_HEAD(pci_host_bridges);
>>> +
>>> +static bool __init 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);
>>> +}
> 
> The two functions above seem to deal with the same resources, e.g. cfg->win
> 
> and map/unmap. Would it make sense to align those, something like
> 
> s/pci_remap_cfgspace/pci_ecam_alloc and pci_ecam_alloc handles cfg->win?
> 
> Or anything which makes them look init/fini style?

Ok will rename the function name.
> 
>>> +
>>> +static struct pci_config_window *gen_pci_init(struct dt_device_node *dev,
>>> +        struct pci_ecam_ops *ops)
>>> +{
>>> +    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 "No bus range found for pci controller\n");
>>> +    } else {
>>> +        if ( cfg->busn_end > cfg->busn_start + 0xff )
>>> +            cfg->busn_end = cfg->busn_start + 0xff;
> 
> So, if bus start is, for example, 0x10 then we'll end up with bus end at 
> (0x10 + 0xff) > 0xff
> 
> which doesn't seem to be what we want

This is to fix if in device tree bus-ranges property, bus end corresponds to 
more than 256 bus.

> 
>>> +    }
>>> +
>>> +    /* Parse our PCI ecam register address*/
>>> +    err = dt_device_get_address(dev, 0, &addr, &size);
>>> +    if ( err )
>>> +        goto err_exit;
>> Shouldn't we handle the possibility of multiple addresses? Is it
>> possible to have more than one range for an ECAM compliant host bridge?
>> 
>> 
>>> +    cfg->phys_addr = addr;
>>> +    cfg->size = size;
>>> +    cfg->ops = ops;
>>> +
>>> +    /*
>>> +     * 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);
> 
> I am fine with "win", but can we think of something that tells us that
> 
> "win" is actually ECAM base address, so one doesn't need to map "win" to 
> "ECAM"
> 
> while reading?

Ack. Will fix.
> 
>>> +    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);
>>> +
>>> +    if ( ops->init ) {
>>> +        err = ops->init(cfg);
>>> +        if (err)
>>> +            goto err_exit;
>>> +    }
>>> +
>>> +    return cfg;
>>> +
>>> +err_exit_remap:
>>> +    printk(XENLOG_ERR "ECAM ioremap failed\n");
>>> +err_exit:
>>> +    pci_ecam_free(cfg);
>>> +    return NULL;
>>> +}
>>> +
>>> +static 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);
>>> +    return bridge;
>>> +}
>>> +
>>> +int pci_host_common_probe(struct dt_device_node *dev,
>>> +        struct pci_ecam_ops *ops)
>>> +{
>>> +    struct pci_host_bridge *bridge;
>>> +    struct pci_config_window *cfg;
>>> +    u32 segment;
>>> +
>>> +    bridge = pci_alloc_host_bridge();
>>> +    if ( !bridge )
>>> +        return -ENOMEM;
>>> +
>>> +    /* Parse and map our Configuration Space windows */
> Do you expect multiple windows here as the comment says?

If going forward we want to support 32-bit we have to ioremap the config space 
for each bus individually, but as of only 64 bit is supported.

>>> +    cfg = gen_pci_init(dev, ops)
>>> +    if ( !cfg )
>>> +        return -ENOMEM;
>> In case of errors the allocated bridge is not freed.
>> 
>> 
>>> +    bridge->dt_node = dev;
>>> +    bridge->sysdata = cfg;
>>> +    bridge->ops = &ops->pci_ops;
> 
> Can we have some sort of dummy ops so we don't have to check for ops != NULL 
> every time
> 
> we read/write config? Is it really possible that we have ops set to NULL 
> after we have
> 
> the development finished?

We don’t want to support host-bridges with dump ops. Proper ops has to be setup 
for the host-bridge to access the read/write. 
Once we access the config space we are sure that ops is already setup so no 
need to check for NULL each time. 

> 
>>> +
>>> +    if( !dt_property_read_u32(dev, "linux,pci-domain", &segment) )
>>> +    {
>>> +        printk(XENLOG_ERR "\"linux,pci-domain\" property in not available 
>>> in DT\n");
>>> +        return -ENODEV;
>>> +    }
>>> +
>>> +    bridge->segment = (u16)segment;
>> My understanding is that a Linux pci-domain doesn't correspond exactly
>> to a PCI segment. See for instance:
>> 
>> https://lists.gnu.org/archive/html/qemu-devel/2018-04/msg03885.html
>> 
>> Do we need to care about the difference? If we mean pci-domain here,
>> should we just call them as such instead of calling them "segments" in
>> Xen (if they are not segments)?
> 
>> 
>> 
>>> +    list_add_tail(&bridge->node, &pci_host_bridges);
>> It looks like &pci_host_bridges should be an ordered list, ordered by
>> segment number?
> 
> Why? Do you expect bridge access in some specific order so ordered
> 
> list will make it faster?

As I mentioned in earlier no need to have ordered list as PCI config space 
access is random.

> 
>> 
>> 
>>> +    return 0;
>>> +}
>>> +
>>> +/*
>>> + * This function will lookup an hostbridge based on the segment and bus
>>> + * number.
>>> + */
>>> +struct pci_host_bridge *pci_find_host_bridge(uint16_t segment, uint8_t bus)
>>> +{
>>> +    struct pci_host_bridge *bridge;
>>> +    bool found = false;
>>> +
>>> +    list_for_each_entry( bridge, &pci_host_bridges, node )
>>> +    {
>>> +        if ( bridge->segment != segment )
>>> +            continue;
>>> +
>>> +        found = true;
>>> +        break;
>>> +    }
>>> +
>>> +    return (found) ? bridge : NULL;
>>> +}
>>> +/*
>>> + * 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..cd67b3dec6
>>> --- /dev/null
>>> +++ b/xen/arch/arm/pci/pci-host-generic.c
>>> @@ -0,0 +1,131 @@
>>> +/*
>>> + * Copyright (C) 2020 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 <asm/io.h>
>>> +#include <xen/pci.h>
>>> +#include <asm/pci.h>
>>> +
>>> +/*
>>> + * Function to get the config space base.
>>> + */
>>> +static void __iomem *pci_config_base(struct pci_host_bridge *bridge,
>>> +        uint32_t sbdf, int where)
>> I think the function is misnamed because reading the code below it looks
>> like it is not just returning the base config space address but also the
>> specific address we need to read/write (adding the device offset,
>> "where", and everything).
>> 
>> Maybe pci_config_get_address or something like that?
>> 
>> 
>>> +{
>>> +    struct pci_config_window *cfg = bridge->sysdata;
> 
> I am a bit confused of the naming ;)
> 
> We already have 2 maps: win -> ECAM base and now sysdata -> cfg.
> 
> Can we please have that aligned somehow so it is easier to follow?

Ack.

> 
>>> +    unsigned int devfn_shift = cfg->ops->bus_shift - 8;
> 
> We are not checking cfg->ops for NULL, so probably we do not want bridges
> 
> with NULL ops as well?

Yes correct we don’t want host-bridge with NULL ops. Do you see any use case to 
have host-bridge with NULL ops?

> 
>>> +
>>> +    pci_sbdf_t sbdf_t = (pci_sbdf_t) sbdf ;
>>> +
>>> +    unsigned int busn = sbdf_t.bus;
>>> +    void __iomem *base;
>>> +
>>> +    if ( busn < cfg->busn_start || busn > cfg->busn_end )
>>> +        return NULL;
>>> +
>>> +    base = cfg->win + (busn << cfg->ops->bus_shift);
>>> +
>>> +    return base + (PCI_DEVFN(sbdf_t.dev, sbdf_t.fn) << devfn_shift) + 
>>> where;
>>> +}
>>> +
>>> +int pci_ecam_config_write(struct pci_host_bridge *bridge, uint32_t sbdf,
>>> +        int where, int size, u32 val)
>>> +{
>>> +    void __iomem *addr;
>>> +
>>> +    addr = pci_config_base(bridge, sbdf, where);
>>> +    if ( !addr )
>>> +        return -ENODEV;
>>> +
>>> +    if ( size == 1 )
>>> +        writeb(val, addr);
>>> +    else if ( size == 2 )
>>> +        writew(val, addr);
>>> +    else
>>> +        writel(val, addr);
>> please use a switch
>> 
>> 
>>> +    return 0;
>>> +}
>>> +
>>> +int pci_ecam_config_read(struct pci_host_bridge *bridge, uint32_t sbdf,
>>> +        int where, int size, u32 *val)
>>> +{
>>> +    void __iomem *addr;
>>> +
>>> +    addr = pci_config_base(bridge, sbdf, where);
>>> +    if ( !addr ) {
>>> +        *val = ~0;
>>> +        return -ENODEV;
>>> +    }
>>> +
>>> +    if ( size == 1 )
>>> +        *val = readb(addr);
>>> +    else if ( size == 2 )
>>> +        *val = readw(addr);
>>> +    else
>>> +        *val = readl(addr);
>> please use a switch
>> 
>> 
>>> +    return 0;
>>> +}
>>> +
>>> +/* ECAM ops */
>>> +struct pci_ecam_ops pci_generic_ecam_ops = {
>>> +    .bus_shift  = 20,
>>> +    .pci_ops    = {
>>> +        .read       = pci_ecam_config_read,
>>> +        .write      = pci_ecam_config_write,
>>> +    }
>>> +};
>>> +
>>> +static const struct dt_device_match gen_pci_dt_match[] = {
>>> +    { .compatible = "pci-host-ecam-generic",
>>> +      .data =       &pci_generic_ecam_ops },
>> spurious blank line
>> 
>> 
>>> +    { },
>>> +};
>>> +
>>> +static int gen_pci_dt_init(struct dt_device_node *dev, const void *data)
>>> +{
>>> +    const struct dt_device_match *of_id;
>>> +    struct pci_ecam_ops *ops;
>>> +
>>> +    of_id = dt_match_node(gen_pci_dt_match, dev->dev.of_node);
>>> +    ops = (struct pci_ecam_ops *) of_id->data;
>>> +
>>> +    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, ops);
>>> +}
>>> +
>>> +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/arch/arm/pci/pci.c b/xen/arch/arm/pci/pci.c
>>> new file mode 100644
>>> index 0000000000..f8cbb99591
>>> --- /dev/null
>>> +++ b/xen/arch/arm/pci/pci.c
>>> @@ -0,0 +1,112 @@
>>> +/*
>>> + * Copyright (C) 2020 Arm Ltd.
>>> + *
>>> + * 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/acpi.h>
>>> +#include <xen/device_tree.h>
>>> +#include <xen/errno.h>
>>> +#include <xen/init.h>
>>> +#include <xen/pci.h>
>>> +#include <xen/param.h>
>>> +
>>> +static int __init dt_pci_init(void)
>>> +{
>>> +    struct dt_device_node *np;
>>> +    int rc;
>>> +
>>> +    dt_for_each_device_node(dt_host, np)
>>> +    {
>>> +        rc = device_init(np, DEVICE_PCI, NULL);
>>> +        if( !rc )
>>> +            continue;
>>> +        /*
>>> +         * Ignore the following error codes:
>>> +         *   - EBADF: Indicate the current is not an pci
>>> +         *   - ENODEV: The pci device is not present or cannot be used by
>>> +         *     Xen.
>>> +         */
>>> +        else if ( rc != -EBADF && rc != -ENODEV )
>>> +        {
>>> +            printk(XENLOG_ERR "No driver found in XEN or driver init 
>>> error.\n");
>>> +            return rc;
>>> +        }
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +#ifdef CONFIG_ACPI
>>> +static void __init acpi_pci_init(void)
>>> +{
>>> +    printk(XENLOG_ERR "ACPI pci init not supported \n");
>>> +    return;
>>> +}
>>> +#else
>>> +static inline void __init acpi_pci_init(void) { }
>>> +#endif
>>> +
>>> +static bool __initdata param_pci_enable;
>>> +static int __init parse_pci_param(const char *arg)
>>> +{
>>> +    if ( !arg )
>>> +    {
>>> +        param_pci_enable = false;
>>> +        return 0;
>>> +    }
>>> +
>>> +    switch ( parse_bool(arg, NULL) )
>>> +    {
>>> +        case 0:
>>> +            param_pci_enable = false;
>>> +            return 0;
>>> +        case 1:
>>> +            param_pci_enable = true;
>>> +            return 0;
>>> +    }
>>> +
>>> +    return -EINVAL;
>>> +}
>>> +custom_param("pci", parse_pci_param);
>> When adding new command line parameters please also add its
>> documentation (docs/misc/xen-command-line.pandoc) in the same patch,
>> unless this is meant to be just transient and we'll get removed before
>> the final commit of the series.
>> 
>> 
>>> +void __init pci_init(void)
>>> +{
>>> +    /*
>>> +     * Enable PCI when has been enabled explicitly (pci=on)
>>> +     */
>>> +    if ( !param_pci_enable)
>>> +        goto disable;
>>> +
>>> +    if ( acpi_disabled )
>>> +        dt_pci_init();
>>> +    else
>>> +        acpi_pci_init();
>>> +
>>> +#ifdef CONFIG_HAS_PCI
>>> +    pci_segments_init();
>>> +#endif
>>> +
>>> +disable:
>>> +    return;
>>> +}
>>> +
>>> +/*
>>> + * 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/setup.c b/xen/arch/arm/setup.c
>>> index 7968cee47d..2d7f1db44f 100644
>>> --- a/xen/arch/arm/setup.c
>>> +++ b/xen/arch/arm/setup.c
>>> @@ -930,6 +930,8 @@ void __init start_xen(unsigned long boot_phys_offset,
>>> 
>>>      setup_virt_paging();
>>> 
>>> +    pci_init();
>> pci_init should probably be an initcall
>> 
>> 
>>>      do_initcalls();
>>> 
>>>      /*
>>> diff --git a/xen/include/asm-arm/device.h b/xen/include/asm-arm/device.h
>>> index ee7cff2d44..28f8049cfd 100644
>>> --- a/xen/include/asm-arm/device.h
>>> +++ b/xen/include/asm-arm/device.h
>>> @@ -4,6 +4,7 @@
>>>  enum device_type
>>>  {
>>>      DEV_DT,
>>> +    DEV_PCI,
>>>  };
>>> 
>>>  struct dev_archdata {
>>> @@ -25,15 +26,15 @@ typedef struct device device_t;
>>> 
>>>  #include <xen/device_tree.h>
>>> 
>>> -/* TODO: Correctly implement dev_is_pci when PCI is supported on ARM */
>>> -#define dev_is_pci(dev) ((void)(dev), 0)
>>> -#define dev_is_dt(dev)  ((dev->type == DEV_DT)
> Didn't we have a patch for that recently or talked about?

Not sure need to check.

>>> +#define dev_is_pci(dev) (dev->type == DEV_PCI)
>>> +#define dev_is_dt(dev)  (dev->type == DEV_DT)
>>> 
>>>  enum device_class
>>>  {
>>>      DEVICE_SERIAL,
>>>      DEVICE_IOMMU,
>>>      DEVICE_GIC,
>>> +    DEVICE_PCI,
>>>      /* Use for error */
>>>      DEVICE_UNKNOWN,
>>>  };
>>> diff --git a/xen/include/asm-arm/pci.h b/xen/include/asm-arm/pci.h
>>> index de13359f65..94fd00360a 100644
>>> --- a/xen/include/asm-arm/pci.h
>>> +++ b/xen/include/asm-arm/pci.h
>>> @@ -1,7 +1,98 @@
>>> -#ifndef __X86_PCI_H__
>>> -#define __X86_PCI_H__
>>> +/*
>>> + * Copyright (C) 2020 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/>.
>>> + */
>>> 
>>> +#ifndef __ARM_PCI_H__
>>> +#define __ARM_PCI_H__
>>> +
>>> +#include <xen/pci.h>
>>> +#include <xen/device_tree.h>
>>> +#include <asm/device.h>
>>> +
>>> +#ifdef CONFIG_ARM_PCI
>>> +
>>> +/* Arch pci dev struct */
>>>  struct arch_pci_dev {
>>> +    struct device dev;
>>> +};
>> Are you actually using struct device in struct arch_pci_dev?
>> struct device is already part of struct dt_device_node and a pointer to
>> it is stored in bridge->dt_node.
>> 
>> 
>>> +#define PRI_pci "%04x:%02x:%02x.%u"
>>> +#define pci_to_dev(pcidev) (&(pcidev)->arch.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;
>>> +    struct pci_ecam_ops     *ops;
>>> +    void __iomem        *win;
>>> +};
>>> +
>>> +/* Forward declaration as pci_host_bridge and pci_ops depend on each 
>>> other. */
>>> +struct pci_host_bridge;
>>> +
>>> +struct pci_ops {
>>> +    int (*read)(struct pci_host_bridge *bridge,
>>> +                    uint32_t sbdf, int where, int size, u32 *val);
>>> +    int (*write)(struct pci_host_bridge *bridge,
>>> +                    uint32_t sbdf, int where, int size, u32 val);
>> I'd prefer if we could use explicitly-sized integers for "where" and
>> "size" too. Also, should they be unsigned rather than signed?
>> 
>> Can we use pci_sbdf_t for the sbdf parameter?
>> 
>> 
>>> +};
>>> +
>>> +/*
>>> + * struct to hold pci ops and bus shift of the config window
>>> + * for a PCI controller.
>>> + */
>>> +struct pci_ecam_ops {
>>> +    unsigned int            bus_shift;
>>> +    struct pci_ops          pci_ops;
>>> +    int             (*init)(struct pci_config_window *);
>>> +};
>> Although I realize that we are only targeting ECAM now, and the
>> implementation is based on ECAM, the interface doesn't seem to have
>> anything ECAM-specific in it. I would rename pci_ecam_ops to something
>> else, maybe simply "pci_ops".
> 
> Yes, please, bear in mind that we are about to work with this code on
> 
> non-ECAM HW from the very beginning, so this is something that we would
> 
> like to see from the ground up

Ok. Will take care of that in next version of the patch.

> 
>> 
>> 
>>> +/*
>>> + * 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 */
>>> +    void *sysdata;                   /* Pointer to the config space 
>>> window*/
>>> +    const struct pci_ops *ops;
>>>  };
>>> 
>>> -#endif /* __X86_PCI_H__ */
>>> +struct pci_host_bridge *pci_find_host_bridge(uint16_t segment, uint8_t 
>>> bus);
>>> +
>>> +int pci_host_common_probe(struct dt_device_node *dev,
>>> +                struct pci_ecam_ops *ops);
>>> +
>>> +void pci_init(void);
>>> +
>>> +#else   /*!CONFIG_ARM_PCI*/
>>> +struct arch_pci_dev { };
>>> +static inline void  pci_init(void) { }
>>> +#endif  /*!CONFIG_ARM_PCI*/
>>> +#endif /* __ARM_PCI_H__ */
>>> -- 
>>> 2.17.1