[PATCH v2 08/15] peci: Add device detection
Dan Williams
dan.j.williams at intel.com
Sat Aug 28 05:01:06 AEST 2021
On Tue, Aug 3, 2021 at 4:35 AM Iwona Winiarska
<iwona.winiarska at intel.com> wrote:
>
> Since PECI devices are discoverable, we can dynamically detect devices
> that are actually available in the system.
>
> This change complements the earlier implementation by rescanning PECI
> bus to detect available devices. For this purpose, it also introduces the
> minimal API for PECI requests.
>
> Signed-off-by: Iwona Winiarska <iwona.winiarska at intel.com>
> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> ---
> drivers/peci/Makefile | 2 +-
> drivers/peci/core.c | 33 ++++++++++++
> drivers/peci/device.c | 114 ++++++++++++++++++++++++++++++++++++++++
> drivers/peci/internal.h | 14 +++++
> drivers/peci/request.c | 50 ++++++++++++++++++
> 5 files changed, 212 insertions(+), 1 deletion(-)
> create mode 100644 drivers/peci/device.c
> create mode 100644 drivers/peci/request.c
>
> diff --git a/drivers/peci/Makefile b/drivers/peci/Makefile
> index 926d8df15cbd..c5f9d3fe21bb 100644
> --- a/drivers/peci/Makefile
> +++ b/drivers/peci/Makefile
> @@ -1,7 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0-only
>
> # Core functionality
> -peci-y := core.o
> +peci-y := core.o request.o device.o
> obj-$(CONFIG_PECI) += peci.o
>
> # Hardware specific bus drivers
> diff --git a/drivers/peci/core.c b/drivers/peci/core.c
> index 7b3938af0396..d143f1a7fe98 100644
> --- a/drivers/peci/core.c
> +++ b/drivers/peci/core.c
> @@ -34,6 +34,20 @@ struct device_type peci_controller_type = {
> .release = peci_controller_dev_release,
> };
>
> +static int peci_controller_scan_devices(struct peci_controller *controller)
> +{
> + int ret;
> + u8 addr;
> +
> + for (addr = PECI_BASE_ADDR; addr < PECI_BASE_ADDR + PECI_DEVICE_NUM_MAX; addr++) {
> + ret = peci_device_create(controller, addr);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> static struct peci_controller *peci_controller_alloc(struct device *dev,
> struct peci_controller_ops *ops)
> {
> @@ -76,10 +90,23 @@ static struct peci_controller *peci_controller_alloc(struct device *dev,
> return ERR_PTR(ret);
> }
>
> +static int unregister_child(struct device *dev, void *dummy)
> +{
> + peci_device_destroy(to_peci_device(dev));
> +
> + return 0;
> +}
> +
> static void unregister_controller(void *_controller)
> {
> struct peci_controller *controller = _controller;
>
> + /*
> + * Detach any active PECI devices. This can't fail, thus we do not
> + * check the returned value.
> + */
> + device_for_each_child_reverse(&controller->dev, NULL, unregister_child);
> +
> device_unregister(&controller->dev);
> }
>
> @@ -115,6 +142,12 @@ struct peci_controller *devm_peci_controller_add(struct device *dev,
> if (ret)
> return ERR_PTR(ret);
>
> + /*
> + * Ignoring retval since failures during scan are non-critical for
> + * controller itself.
> + */
> + peci_controller_scan_devices(controller);
> +
> return controller;
>
> err:
> diff --git a/drivers/peci/device.c b/drivers/peci/device.c
> new file mode 100644
> index 000000000000..32811248997b
> --- /dev/null
> +++ b/drivers/peci/device.c
> @@ -0,0 +1,114 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (c) 2018-2021 Intel Corporation
> +
> +#include <linux/peci.h>
> +#include <linux/slab.h>
> +
> +#include "internal.h"
> +
> +static int peci_detect(struct peci_controller *controller, u8 addr)
> +{
> + struct peci_request *req;
> + int ret;
> +
> + /*
> + * PECI Ping is a command encoded by tx_len = 0, rx_len = 0.
> + * We expect correct Write FCS if the device at the target address
> + * is able to respond.
> + */
> + req = peci_request_alloc(NULL, 0, 0);
> + if (!req)
> + return -ENOMEM;
Seems a waste to do a heap allocation for this routine. Why not:
/*
* PECI Ping is a command encoded by tx_len = 0, rx_len = 0.
* We expect correct Write FCS if the device at the target address
* is able to respond.
*/
struct peci_request req = { 0 };
> +
> + mutex_lock(&controller->bus_lock);
> + ret = controller->ops->xfer(controller, addr, req);
> + mutex_unlock(&controller->bus_lock);
> +
> + peci_request_free(req);
> +
> + return ret;
> +}
> +
> +static bool peci_addr_valid(u8 addr)
> +{
> + return addr >= PECI_BASE_ADDR && addr < PECI_BASE_ADDR + PECI_DEVICE_NUM_MAX;
> +}
> +
> +static int peci_dev_exists(struct device *dev, void *data)
> +{
> + struct peci_device *device = to_peci_device(dev);
> + u8 *addr = data;
> +
> + if (device->addr == *addr)
> + return -EBUSY;
> +
> + return 0;
> +}
> +
> +int peci_device_create(struct peci_controller *controller, u8 addr)
> +{
> + struct peci_device *device;
> + int ret;
> +
> + if (WARN_ON(!peci_addr_valid(addr)))
The WARN_ON is overkill, especially as there is only one caller of
this and it loops through valid addresses.
> + return -EINVAL;
> +
> + /* Check if we have already detected this device before. */
> + ret = device_for_each_child(&controller->dev, &addr, peci_dev_exists);
> + if (ret)
> + return 0;
> +
> + ret = peci_detect(controller, addr);
> + if (ret) {
> + /*
> + * Device not present or host state doesn't allow successful
> + * detection at this time.
> + */
> + if (ret == -EIO || ret == -ETIMEDOUT)
> + return 0;
> +
> + return ret;
> + }
> +
> + device = kzalloc(sizeof(*device), GFP_KERNEL);
> + if (!device)
> + return -ENOMEM;
> +
> + device->addr = addr;
> + device->dev.parent = &controller->dev;
> + device->dev.bus = &peci_bus_type;
> + device->dev.type = &peci_device_type;
> +
> + ret = dev_set_name(&device->dev, "%d-%02x", controller->id, device->addr);
> + if (ret)
> + goto err_free;
It's cleaner to just have one unified error exit using put_device().
Use the device_initialize() + device_add() pattern, not
device_register().
> +
> + ret = device_register(&device->dev);
> + if (ret)
> + goto err_put;
> +
> + return 0;
> +
> +err_put:
> + put_device(&device->dev);
> +err_free:
> + kfree(device);
> +
> + return ret;
> +}
> +
> +void peci_device_destroy(struct peci_device *device)
> +{
> + device_unregister(&device->dev);
No clear value for this wrapper, in fact in one caller it causes it to
do a to_peci_device() just this helper can undo that up-cast.
> +}
> +
> +static void peci_device_release(struct device *dev)
> +{
> + struct peci_device *device = to_peci_device(dev);
> +
> + kfree(device);
> +}
> +
> +struct device_type peci_device_type = {
> + .release = peci_device_release,
> +};
> diff --git a/drivers/peci/internal.h b/drivers/peci/internal.h
> index 918dea745a86..57d11a902c5d 100644
> --- a/drivers/peci/internal.h
> +++ b/drivers/peci/internal.h
> @@ -8,6 +8,20 @@
> #include <linux/types.h>
>
> struct peci_controller;
> +struct peci_device;
> +struct peci_request;
> +
> +/* PECI CPU address range 0x30-0x37 */
> +#define PECI_BASE_ADDR 0x30
> +#define PECI_DEVICE_NUM_MAX 8
> +
> +struct peci_request *peci_request_alloc(struct peci_device *device, u8 tx_len, u8 rx_len);
> +void peci_request_free(struct peci_request *req);
> +
> +extern struct device_type peci_device_type;
> +
> +int peci_device_create(struct peci_controller *controller, u8 addr);
> +void peci_device_destroy(struct peci_device *device);
>
> extern struct bus_type peci_bus_type;
>
> diff --git a/drivers/peci/request.c b/drivers/peci/request.c
> new file mode 100644
> index 000000000000..81b567bc7b87
> --- /dev/null
> +++ b/drivers/peci/request.c
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (c) 2021 Intel Corporation
> +
> +#include <linux/export.h>
> +#include <linux/peci.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +#include "internal.h"
> +
> +/**
> + * peci_request_alloc() - allocate &struct peci_requests
> + * @device: PECI device to which request is going to be sent
> + * @tx_len: TX length
> + * @rx_len: RX length
> + *
> + * Return: A pointer to a newly allocated &struct peci_request on success or NULL otherwise.
> + */
> +struct peci_request *peci_request_alloc(struct peci_device *device, u8 tx_len, u8 rx_len)
> +{
> + struct peci_request *req;
> +
> + if (WARN_ON_ONCE(tx_len > PECI_REQUEST_MAX_BUF_SIZE || rx_len > PECI_REQUEST_MAX_BUF_SIZE))
WARN_ON_ONCE() should only be here to help other kernel developers not
make this mistake However, another way to enforce this is to stop
exporting peci_request_alloc() and instead export helpers for specific
command types, and keep this detail internal to the core. If you keep
this, it needs a comment that it is only here to warn other
peci-client developers of their bug before it goes upstream.
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