Re: [PATCH V3 XRT Alveo 04/18] fpga: xrt: xrt-lib platform driver manager

Moritz Fischer
2021-02-23T03:36:53Z

On Mon, Feb 22, 2021 at 07:05:29AM -0800, Tom Rix wrote:
>
> On 2/17/21 10:40 PM, Lizhi Hou wrote:
> > xrt-lib kernel module infrastructure code to register and manage all
> > leaf driver modules.
> >
> > Signed-off-by: Sonal Santan <sonal.santan@xilinx.com>
> > Signed-off-by: Max Zhen <max.zhen@xilinx.com>
> > Signed-off-by: Lizhi Hou <lizhih@xilinx.com>
> > ---
> > drivers/fpga/xrt/lib/main.c | 274 ++++++++++++++++++++++++++++++++++++
> > drivers/fpga/xrt/lib/main.h | 17 +++
> > 2 files changed, 291 insertions(+)
> > create mode 100644 drivers/fpga/xrt/lib/main.c
> > create mode 100644 drivers/fpga/xrt/lib/main.h
>
> Not sure if 'main' is a good base name for something going into a lib.
>
> >
> > diff --git a/drivers/fpga/xrt/lib/main.c b/drivers/fpga/xrt/lib/main.c
> > new file mode 100644
> > index 000000000000..36fb62710843
> > --- /dev/null
> > +++ b/drivers/fpga/xrt/lib/main.c
> > @@ -0,0 +1,274 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Driver for Xilinx Alveo FPGA Support
> > + *
> > + * Copyright (C) 2020-2021 Xilinx, Inc.
> > + *
> > + * Authors:
> > + * Cheng Zhen <maxz@xilinx.com>
> > + */
> > +
> > +#include <linux/module.h>
> > +#include "xleaf.h"
> > +#include "xroot.h"
> > +#include "main.h"
> > +
> > +#define XRT_IPLIB_MODULE_NAME "xrt-lib"
> > +#define XRT_IPLIB_MODULE_VERSION "4.0.0"
> > +#define XRT_MAX_DEVICE_NODES 128
> > +#define XRT_DRVNAME(drv) ((drv)->driver.name)
> > +
> > +/*
> > + * Subdev driver is known by ID to others. We map the ID to it's
> by it's ID
> > + * struct platform_driver, which contains it's binding name and driver/file ops.
> > + * We also map it to the endpoint name in DTB as well, if it's different
> > + * than the driver's binding name.
> > + */
> > +struct xrt_drv_map {
> > + struct list_head list;
> > + enum xrt_subdev_id id;
> > + struct platform_driver *drv;
> > + struct xrt_subdev_endpoints *eps;
> > + struct ida ida; /* manage driver instance and char dev minor */
> > +};
> > +
> > +static DEFINE_MUTEX(xrt_lib_lock); /* global lock protecting xrt_drv_maps list */
> > +static LIST_HEAD(xrt_drv_maps);
> > +struct class *xrt_class;
> > +
> > +static inline struct xrt_subdev_drvdata *
> > +xrt_drv_map2drvdata(struct xrt_drv_map *map)
> > +{
> > + return (struct xrt_subdev_drvdata *)map->drv->id_table[0].driver_data;
> > +}
> > +
> > +static struct xrt_drv_map *
> > +xrt_drv_find_map_by_id_nolock(enum xrt_subdev_id id)
>
> name could be by convention
>
> __xrt_drv_find_map_id
>
> > +{
> > + const struct list_head *ptr;
> > +
> > + list_for_each(ptr, &xrt_drv_maps) {
> > + struct xrt_drv_map *tmap = list_entry(ptr, struct xrt_drv_map, list);
> > +
> > + if (tmap->id == id)
> > + return tmap;
> > + }
> > + return NULL;
> > +}
> > +
> > +static struct xrt_drv_map *
> > +xrt_drv_find_map_by_id(enum xrt_subdev_id id)
> > +{
> > + struct xrt_drv_map *map;
> > +
> > + mutex_lock(&xrt_lib_lock);
> > + map = xrt_drv_find_map_by_id_nolock(id);
> > + mutex_unlock(&xrt_lib_lock);
> > + /*
> > + * map should remain valid even after lock is dropped since a registered
> even after the lock
> > + * driver should only be unregistered when driver module is being unloaded,
> > + * which means that the driver should not be used by then.
> > + */
> > + return map;
> > +}
> > +
> > +static int xrt_drv_register_driver(struct xrt_drv_map *map)
> > +{
> > + struct xrt_subdev_drvdata *drvdata;
> > + int rc = 0;
> > + const char *drvname = XRT_DRVNAME(map->drv);
> > +
> > + rc = platform_driver_register(map->drv);
> > + if (rc) {
> > + pr_err("register %s platform driver failed\n", drvname);
> > + return rc;
> > + }
> > +
> > + drvdata = xrt_drv_map2drvdata(map);
> > + if (drvdata) {
> > + /* Initialize dev_t for char dev node. */
> > + if (xleaf_devnode_enabled(drvdata)) {
> > + rc = alloc_chrdev_region(&drvdata->xsd_file_ops.xsf_dev_t, 0,
> > + XRT_MAX_DEVICE_NODES, drvname);
> > + if (rc) {
> > + platform_driver_unregister(map->drv);
> > + pr_err("failed to alloc dev minor for %s: %d\n", drvname, rc);
> > + return rc;
> > + }
> > + } else {
> > + drvdata->xsd_file_ops.xsf_dev_t = (dev_t)-1;
> > + }
> > + }
> > +
> > + ida_init(&map->ida);
> > +
> > + pr_info("%s registered successfully\n", drvname);
> > +
> > + return 0;
> > +}
> > +
> > +static void xrt_drv_unregister_driver(struct xrt_drv_map *map)
> > +{
> > + const char *drvname = XRT_DRVNAME(map->drv);
> > + struct xrt_subdev_drvdata *drvdata;
> > +
> > + ida_destroy(&map->ida);
> > +
> > + drvdata = xrt_drv_map2drvdata(map);
> > + if (drvdata && drvdata->xsd_file_ops.xsf_dev_t != (dev_t)-1) {
> > + unregister_chrdev_region(drvdata->xsd_file_ops.xsf_dev_t,
> > + XRT_MAX_DEVICE_NODES);
> > + }
> > +
> > + platform_driver_unregister(map->drv);
> > +
> > + pr_info("%s unregistered successfully\n", drvname);
> > +}
> > +
> > +int xleaf_register_driver(enum xrt_subdev_id id,
> > + struct platform_driver *drv,
> > + struct xrt_subdev_endpoints *eps)
> > +{
> > + struct xrt_drv_map *map;
> > +
> > + mutex_lock(&xrt_lib_lock);
>
> Trying to minimize length of lock being held.
>
> Could holding this lock be split or the alloc moved above ?
>
> > +
> > + map = xrt_drv_find_map_by_id_nolock(id);
> > + if (map) {
> > + mutex_unlock(&xrt_lib_lock);
> > + pr_err("Id %d already has a registered driver, 0x%p\n",
> > + id, map->drv);
> > + return -EEXIST;
> > + }
> > +
> > + map = vzalloc(sizeof(*map));
>
> general issue
>
> map is small, so kzalloc
>
> > + if (!map) {
> > + mutex_unlock(&xrt_lib_lock);
> > + return -ENOMEM;
> > + }
> > + map->id = id;
> > + map->drv = drv;
> > + map->eps = eps;
> > +
> > + xrt_drv_register_driver(map);
>
> xrt_drv_register_driver failure is unhandled.
>
> This is the only time xrt_drv_register_driver is called, consider expanding the function here and removing the call.
>
> > +
> > + list_add(&map->list, &xrt_drv_maps);
> > +
> > + mutex_unlock(&xrt_lib_lock);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(xleaf_register_driver);
> > +
> > +void xleaf_unregister_driver(enum xrt_subdev_id id)
> > +{
> > + struct xrt_drv_map *map;
> > +
> > + mutex_lock(&xrt_lib_lock);
> > +
> > + map = xrt_drv_find_map_by_id_nolock(id);
> > + if (!map) {
> > + mutex_unlock(&xrt_lib_lock);
> > + pr_err("Id %d has no registered driver\n", id);
> > + return;
> > + }
> > +
> > + list_del(&map->list);
> > +
> > + mutex_unlock(&xrt_lib_lock);
> > +
> > + xrt_drv_unregister_driver(map);
> > + vfree(map);
> > +}
> > +EXPORT_SYMBOL_GPL(xleaf_unregister_driver);
> > +
> > +const char *xrt_drv_name(enum xrt_subdev_id id)
> > +{
> > + struct xrt_drv_map *map = xrt_drv_find_map_by_id(id);
> > +
> > + if (map)
> > + return XRT_DRVNAME(map->drv);
> > + return NULL;
> > +}
> > +
> > +int xrt_drv_get_instance(enum xrt_subdev_id id)
> > +{
> > + struct xrt_drv_map *map = xrt_drv_find_map_by_id(id);
> > +
> > + return ida_alloc_range(&map->ida, 0, XRT_MAX_DEVICE_NODES, GFP_KERNEL);
> > +}
> > +
> > +void xrt_drv_put_instance(enum xrt_subdev_id id, int instance)
> > +{
> > + struct xrt_drv_map *map = xrt_drv_find_map_by_id(id);
> > +
> > + ida_free(&map->ida, instance);
> > +}
> > +
> > +struct xrt_subdev_endpoints *xrt_drv_get_endpoints(enum xrt_subdev_id id)
> > +{
> > + struct xrt_drv_map *map = xrt_drv_find_map_by_id(id);
> > + struct xrt_subdev_endpoints *eps;
> > +
> > + eps = map ? map->eps : NULL;
> > + return eps;
> > +}
> > +
> > +/* Leaf driver's module init/fini callbacks. */
>
> These constructor/destructor calls needs to be more dynamic.
>
> calls are made even if there are no subdevices to go with the id's.
>
> Also this list can not grow.  How would a new id be added by a module ?
>
> > +static void (*leaf_init_fini_cbs[])(bool) = {
> > + group_leaf_init_fini,
> > + vsec_leaf_init_fini,
> > + devctl_leaf_init_fini,
> > + axigate_leaf_init_fini,
> > + icap_leaf_init_fini,
> > + calib_leaf_init_fini,
> > + clkfreq_leaf_init_fini,
> > + clock_leaf_init_fini,
> > + ucs_leaf_init_fini,
> > +};
> > +
> > +static __init int xrt_lib_init(void)
> > +{
> > + int i;
> > +
> > + xrt_class = class_create(THIS_MODULE, XRT_IPLIB_MODULE_NAME);
> > + if (IS_ERR(xrt_class))
> > + return PTR_ERR(xrt_class);
> > +
> > + for (i = 0; i < ARRAY_SIZE(leaf_init_fini_cbs); i++)
> > + leaf_init_fini_cbs[i](true);
> > + return 0;
> > +}
> > +
> > +static __exit void xrt_lib_fini(void)
> > +{
> > + struct xrt_drv_map *map;
> > + int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(leaf_init_fini_cbs); i++)
> > + leaf_init_fini_cbs[i](false);
> > +
> > + mutex_lock(&xrt_lib_lock);
> > +
> > + while (!list_empty(&xrt_drv_maps)) {
> > + map = list_first_entry_or_null(&xrt_drv_maps, struct xrt_drv_map, list);
> > + pr_err("Unloading module with %s still registered\n", XRT_DRVNAME(map->drv));
> > + list_del(&map->list);
> > + mutex_unlock(&xrt_lib_lock);
> > + xrt_drv_unregister_driver(map);
> > + vfree(map);
> > + mutex_lock(&xrt_lib_lock);
> > + }
> > +
> > + mutex_unlock(&xrt_lib_lock);
> > +
> > + class_destroy(xrt_class);
> > +}
> > +
> > +module_init(xrt_lib_init);
> > +module_exit(xrt_lib_fini);
> > +
> > +MODULE_VERSION(XRT_IPLIB_MODULE_VERSION);
> > +MODULE_AUTHOR("XRT Team <runtime@xilinx.com>");
> > +MODULE_DESCRIPTION("Xilinx Alveo IP Lib driver");
> > +MODULE_LICENSE("GPL v2");
> > diff --git a/drivers/fpga/xrt/lib/main.h b/drivers/fpga/xrt/lib/main.h
> > new file mode 100644
> > index 000000000000..f3bfc87ee614
> > --- /dev/null
> > +++ b/drivers/fpga/xrt/lib/main.h
> > @@ -0,0 +1,17 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2020-2021 Xilinx, Inc.
> > + *
> > + * Authors:
> > + * Cheng Zhen <maxz@xilinx.com>
> > + */
> > +
> > +#ifndef _XRT_MAIN_H_
> > +#define _XRT_MAIN_H_
> > +
> > +const char *xrt_drv_name(enum xrt_subdev_id id);
>
> To be self contained, the header defining enum xrt_subdev_id should be included.
>
> This is subdev_id.h which comes in with patch 6
>
> A dependency on a future patch breaks bisectablity.
>
> It may make sense to collect these small headers into a single large header for the ip infra lib and bring them all in this patch.

Please add the headers when you use them, do *not* do header only commits.

It's perfectly fine (and desirable) to add things over time to a header
as you use them.

Note *each* commit must compile and work standing on its own, so yes as
Tom pointed out, do not depend on future (later commit) files.

>
> Tom
>
> > +int xrt_drv_get_instance(enum xrt_subdev_id id);
> > +void xrt_drv_put_instance(enum xrt_subdev_id id, int instance);
> > +struct xrt_subdev_endpoints *xrt_drv_get_endpoints(enum xrt_subdev_id id);
> > +
> > +#endif /* _XRT_MAIN_H_ */
>

- Moritz