On Sat, 5 Jun 2021 23:05:17 -0700
Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> In preparation for infrastructure that enumerates and configures the CXL
> decode mechanism of an upstream port to its downstream ports, add a
> representation for a CXL downstream port.
>
> On ACPI systems the top-most logical downstream ports in the hierarchy
> are the host bridges (ACPI0016 devices) that decode the memory windows
> described by the CXL Early Discovery Table Fixed Memory Window
> Structures (CEDT.CFMWS).
>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> Documentation/ABI/testing/sysfs-bus-cxl | 13 ++++
> drivers/cxl/acpi.c | 44 ++++++++++++++
> drivers/cxl/core.c | 95 ++++++++++++++++++++++++++++++-
> drivers/cxl/cxl.h | 21 +++++++
> 4 files changed, 169 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> index fb996ced7629..0cb31b7ad17b 100644
> --- a/Documentation/ABI/testing/sysfs-bus-cxl
> +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> @@ -35,3 +35,16 @@ Description:
> CXL component registers. The 'uport' symlink connects the CXL
> portX object to the device that published the CXL port
> capability.
> +
> +What: /sys/bus/cxl/devices/portX/dportY
> +Date: June, 2021
> +KernelVersion: v5.14
> +Contact: linux-cxl@xxxxxxxxxxxxxxx
> +Description:
> + CXL port objects are enumerated from either a platform firmware
> + device (ACPI0017 and ACPI0016) or PCIe switch upstream port with
> + CXL component registers. The 'dportY' symlink identifies one or
> + more downstream ports that the upstream port may target in its
> + decode of CXL memory resources. The 'Y' integer reflects the
> + hardware port unique-id used in the hardware decoder target
> + list.
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 556d25ab6966..0ae7464b603d 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -5,19 +5,61 @@
> #include <linux/device.h>
> #include <linux/kernel.h>
> #include <linux/acpi.h>
> +#include <linux/pci.h>
Not immediately seeing why this include is added in this patch.
> #include "cxl.h"
>
> +static struct acpi_device *to_cxl_host_bridge(struct device *dev)
> +{
> + struct acpi_device *adev = to_acpi_device(dev);
> +
> + if (strcmp(acpi_device_hid(adev), "ACPI0016") == 0)
> + return adev;
> + return NULL;
> +}
> +
> +static int add_host_bridge_dport(struct device *match, void *arg)
> +{
> + int rc;
> + acpi_status status;
> + unsigned long long uid;
> + struct cxl_port *root_port = arg;
> + struct device *host = root_port->dev.parent;
> + struct acpi_device *bridge = to_cxl_host_bridge(match);
> +
> + if (!bridge)
> + return 0;
> +
> + status = acpi_evaluate_integer(bridge->handle, METHOD_NAME__UID, NULL,
> + &uid);
> + if (status != AE_OK) {
> + dev_err(host, "unable to retrieve _UID of %s\n",
> + dev_name(match));
> + return -ENODEV;
> + }
> +
> + rc = cxl_add_dport(root_port, match, uid, CXL_RESOURCE_NONE);
> + if (rc) {
> + dev_err(host, "failed to add downstream port: %s\n",
> + dev_name(match));
> + return rc;
> + }
> + dev_dbg(host, "add dport%llu: %s\n", uid, dev_name(match));
> + return 0;
> +}
> +
> static int cxl_acpi_probe(struct platform_device *pdev)
> {
> struct cxl_port *root_port;
> struct device *host = &pdev->dev;
> + struct acpi_device *adev = ACPI_COMPANION(host);
>
> root_port = devm_cxl_add_port(host, host, CXL_RESOURCE_NONE, NULL);
> if (IS_ERR(root_port))
> return PTR_ERR(root_port);
> dev_dbg(host, "add: %s\n", dev_name(&root_port->dev));
>
> - return 0;
> + return bus_for_each_dev(adev->dev.bus, NULL, root_port,
> + add_host_bridge_dport);
> }
>
> static const struct acpi_device_id cxl_acpi_ids[] = {
> diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
> index dbbb34618d7d..4418b30cce4f 100644
> --- a/drivers/cxl/core.c
> +++ b/drivers/cxl/core.c
> @@ -33,10 +33,22 @@ static struct attribute_group cxl_base_attribute_group = {
> .attrs = cxl_base_attributes,
> };
>
> +static void cxl_dport_release(struct cxl_dport *dport)
> +{
> + put_device(dport->dport);
> + list_del(&dport->list);
This ordering isn't the reverse of what happens cxl_add_dport()
That would be
list_del()
put_device()
kfree()
If there is a strong reason for that I'd like to see a comment here.
> + kfree(dport);
> +}
> +
> static void cxl_port_release(struct device *dev)
> {
> struct cxl_port *port = to_cxl_port(dev);
> + struct cxl_dport *dport, *_d;
>
> + device_lock(dev);
> + list_for_each_entry_safe(dport, _d, &port->dports, list)
> + cxl_dport_release(dport);
> + device_unlock(dev);
> ida_free(&cxl_port_ida, port->id);
> kfree(port);
> }
> @@ -60,9 +72,22 @@ struct cxl_port *to_cxl_port(struct device *dev)
> return container_of(dev, struct cxl_port, dev);
> }
>
> -static void unregister_dev(void *dev)
> +static void unregister_port(void *_port)
> {
> - device_unregister(dev);
> + struct cxl_port *port = _port;
> + struct cxl_dport *dport;
> +
> + device_lock(&port->dev);
> + list_for_each_entry(dport, &port->dports, list) {
> + char link_name[CXL_TARGET_STRLEN];
> +
> + if (snprintf(link_name, CXL_TARGET_STRLEN, "dport%d",
> + dport->port_id) >= CXL_TARGET_STRLEN)
> + continue;
> + sysfs_remove_link(&port->dev.kobj, link_name);
> + }
> + device_unlock(&port->dev);
> + device_unregister(&port->dev);
> }
>
> static void cxl_unlink_uport(void *_port)
> @@ -113,6 +138,7 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
>
> port->uport = uport;
> port->component_reg_phys = component_reg_phys;
> + INIT_LIST_HEAD(&port->dports);
>
> device_initialize(dev);
> device_set_pm_not_required(dev);
> @@ -157,7 +183,7 @@ struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
> if (rc)
> goto err;
>
> - rc = devm_add_action_or_reset(host, unregister_dev, dev);
> + rc = devm_add_action_or_reset(host, unregister_port, port);
> if (rc)
> return ERR_PTR(rc);
>
> @@ -173,6 +199,69 @@ struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
> }
> EXPORT_SYMBOL_GPL(devm_cxl_add_port);
>
> +static int add_dport(struct cxl_port *port, struct cxl_dport *new)
> +{
> + struct cxl_dport *dport, *dup = NULL;
> +
> + device_lock(&port->dev);
> + list_for_each_entry (dport, &port->dports, list)
> + if (new->port_id == dport->port_id) {
> + dup = dport;
> + goto err;
> + }
> + list_add_tail(&new->list, &port->dports);
> + device_unlock(&port->dev);
> +
> + return 0;
> +
> +err:
> + device_unlock(&port->dev);
> + dev_err(&port->dev,
> + "unable to add dport%d-%s non-unique port id (%s)\n",
> + new->port_id, dev_name(new->dport), dev_name(dup->dport));
As there is potential that you might end up with other errors in here long term,
why not move this to the point where the error is detected?
I think you are fine doing it under the mutex. Obviously indent will be a deeper
than ideal.
> + return -EEXIST;
> +}
> +
> +/*
This is a bit inconsistent wrt to what functions get full kernel-doc.
My personal preference would be all the exported functions + any others
where it is particularly useful.
> + * Append downstream port data to a cxl_port, note that all allocations
> + * and links are undone by cxl_port deletion and release.
> + */
> +int cxl_add_dport(struct cxl_port *port, struct device *dport_dev, int port_id,
> + resource_size_t component_reg_phys)
> +{
> + char link_name[CXL_TARGET_STRLEN];
> + struct cxl_dport *dport;
> + int rc;
> +
> + if (snprintf(link_name, CXL_TARGET_STRLEN, "dport%d", port_id) >=
> + CXL_TARGET_STRLEN)
> + return -EINVAL;
> +
> + dport = kzalloc(sizeof(*dport), GFP_KERNEL);
> + if (!dport)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&dport->list);
> + dport->dport = get_device(dport_dev);
> + dport->port_id = port_id;
> + dport->component_reg_phys = component_reg_phys;
> + dport->port = port;
> +
> + rc = add_dport(port, dport);
> + if (rc)
If you get an error here, it's not been added to the list, but
in the cxl_dport_release() you remove it from the list. I think you
just want to put and free the device here.
> + goto err;
> +
> + rc = sysfs_create_link(&port->dev.kobj, &dport_dev->kobj, link_name);
> + if (rc)
> + goto err;
> +
> + return 0;
> +err:
> + cxl_dport_release(dport);
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(cxl_add_dport);
> +
> /**
> * cxl_probe_component_regs() - Detect CXL Component register blocks
> * @dev: Host device of the @base mapping
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 46c81165c210..0b89fcfe728a 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -146,6 +146,7 @@ int cxl_map_device_regs(struct pci_dev *pdev,
> struct cxl_register_map *map);
>
> #define CXL_RESOURCE_NONE ((resource_size_t) -1)
> +#define CXL_TARGET_STRLEN 20
>
> /**
> * struct cxl_port - logical collection of upstream port devices and
> @@ -154,19 +155,39 @@ int cxl_map_device_regs(struct pci_dev *pdev,
> * @dev: this port's device
> * @uport: PCI or platform device implementing the upstream port capability
> * @id: id for port device-name
> + * @dports: cxl_dport instances referenced by decoders
> * @component_regs_phys: component register capability base address (optional)
> */
> struct cxl_port {
> struct device dev;
> struct device *uport;
> int id;
> + struct list_head dports;
> resource_size_t component_reg_phys;
> };
>
> +/**
> + * struct cxl_dport - CXL downstream port
> + * @dport: PCI bridge or firmware device representing the downstream link
> + * @port_id: unique hardware identifier for dport in decoder target list
> + * @component_reg_phys: downstream port component registers
> + * @port: reference to cxl_port that contains this downstream port
> + * @list: node for a cxl_port's list of cxl_dport instances
> + */
> +struct cxl_dport {
> + struct device *dport;
> + int port_id;
> + resource_size_t component_reg_phys;
> + struct cxl_port *port;
> + struct list_head list;
> +};
> +
> struct cxl_port *to_cxl_port(struct device *dev);
> struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
> resource_size_t component_reg_phys,
> struct cxl_port *parent_port);
>
> +int cxl_add_dport(struct cxl_port *port, struct device *dport, int port_id,
> + resource_size_t component_reg_phys);
> extern struct bus_type cxl_bus_type;
> #endif /* __CXL_H__ */
>
