diff options
Diffstat (limited to 'drivers/gpio/gpio-virtio.c')
| -rw-r--r-- | drivers/gpio/gpio-virtio.c | 374 |
1 files changed, 374 insertions, 0 deletions
diff --git a/drivers/gpio/gpio-virtio.c b/drivers/gpio/gpio-virtio.c new file mode 100644 index 000000000000..d24f1c9264bc --- /dev/null +++ b/drivers/gpio/gpio-virtio.c @@ -0,0 +1,374 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * GPIO driver for virtio-based virtual GPIO controllers + * + * Copyright (C) 2021 metux IT consult + * Enrico Weigelt, metux IT consult <info@metux.net> + * + * Copyright (C) 2021 Linaro. + * Viresh Kumar <viresh.kumar@linaro.org> + */ + +#include <linux/completion.h> +#include <linux/err.h> +#include <linux/gpio/driver.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/virtio_config.h> +#include <uapi/linux/virtio_gpio.h> +#include <uapi/linux/virtio_ids.h> + +struct virtio_gpio_line { + struct mutex lock; /* Protects line operation */ + struct completion completion; + struct virtio_gpio_request req ____cacheline_aligned; + struct virtio_gpio_response res ____cacheline_aligned; + unsigned int rxlen; +}; + +struct virtio_gpio { + struct virtio_device *vdev; + struct mutex lock; /* Protects virtqueue operation */ + struct gpio_chip gc; + struct virtio_gpio_line *lines; + struct virtqueue *request_vq; +}; + +static int _virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio, + u8 txvalue, u8 *rxvalue, void *response, u32 rxlen) +{ + struct virtio_gpio_line *line = &vgpio->lines[gpio]; + struct virtio_gpio_request *req = &line->req; + struct virtio_gpio_response *res = response; + struct scatterlist *sgs[2], req_sg, res_sg; + struct device *dev = &vgpio->vdev->dev; + int ret; + + /* + * Prevent concurrent requests for the same line since we have + * pre-allocated request/response buffers for each GPIO line. Moreover + * Linux always accesses a GPIO line sequentially, so this locking shall + * always go through without any delays. + */ + mutex_lock(&line->lock); + + req->type = cpu_to_le16(type); + req->gpio = cpu_to_le16(gpio); + req->value = cpu_to_le32(txvalue); + + sg_init_one(&req_sg, req, sizeof(*req)); + sg_init_one(&res_sg, res, rxlen); + sgs[0] = &req_sg; + sgs[1] = &res_sg; + + line->rxlen = 0; + reinit_completion(&line->completion); + + /* + * Virtqueue callers need to ensure they don't call its APIs with other + * virtqueue operations at the same time. + */ + mutex_lock(&vgpio->lock); + ret = virtqueue_add_sgs(vgpio->request_vq, sgs, 1, 1, line, GFP_KERNEL); + if (ret) { + dev_err(dev, "failed to add request to vq\n"); + mutex_unlock(&vgpio->lock); + goto out; + } + + virtqueue_kick(vgpio->request_vq); + mutex_unlock(&vgpio->lock); + + if (!wait_for_completion_timeout(&line->completion, HZ)) { + dev_err(dev, "GPIO operation timed out\n"); + ret = -ETIMEDOUT; + goto out; + } + + if (unlikely(res->status != VIRTIO_GPIO_STATUS_OK)) { + dev_err(dev, "GPIO request failed: %d\n", gpio); + ret = -EINVAL; + goto out; + } + + if (unlikely(line->rxlen != rxlen)) { + dev_err(dev, "GPIO operation returned incorrect len (%u : %u)\n", + rxlen, line->rxlen); + ret = -EINVAL; + goto out; + } + + if (rxvalue) + *rxvalue = res->value; + +out: + mutex_unlock(&line->lock); + return ret; +} + +static int virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio, + u8 txvalue, u8 *rxvalue) +{ + struct virtio_gpio_line *line = &vgpio->lines[gpio]; + struct virtio_gpio_response *res = &line->res; + + return _virtio_gpio_req(vgpio, type, gpio, txvalue, rxvalue, res, + sizeof(*res)); +} + +static void virtio_gpio_free(struct gpio_chip *gc, unsigned int gpio) +{ + struct virtio_gpio *vgpio = gpiochip_get_data(gc); + + virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio, + VIRTIO_GPIO_DIRECTION_NONE, NULL); +} + +static int virtio_gpio_get_direction(struct gpio_chip *gc, unsigned int gpio) +{ + struct virtio_gpio *vgpio = gpiochip_get_data(gc); + u8 direction; + int ret; + + ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_DIRECTION, gpio, 0, + &direction); + if (ret) + return ret; + + switch (direction) { + case VIRTIO_GPIO_DIRECTION_IN: + return GPIO_LINE_DIRECTION_IN; + case VIRTIO_GPIO_DIRECTION_OUT: + return GPIO_LINE_DIRECTION_OUT; + default: + return -EINVAL; + } +} + +static int virtio_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio) +{ + struct virtio_gpio *vgpio = gpiochip_get_data(gc); + + return virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio, + VIRTIO_GPIO_DIRECTION_IN, NULL); +} + +static int virtio_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio, + int value) +{ + struct virtio_gpio *vgpio = gpiochip_get_data(gc); + int ret; + + ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_VALUE, gpio, value, NULL); + if (ret) + return ret; + + return virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_DIRECTION, gpio, + VIRTIO_GPIO_DIRECTION_OUT, NULL); +} + +static int virtio_gpio_get(struct gpio_chip *gc, unsigned int gpio) +{ + struct virtio_gpio *vgpio = gpiochip_get_data(gc); + u8 value; + int ret; + + ret = virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_VALUE, gpio, 0, &value); + return ret ? ret : value; +} + +static void virtio_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value) +{ + struct virtio_gpio *vgpio = gpiochip_get_data(gc); + + virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_SET_VALUE, gpio, value, NULL); +} + +static void virtio_gpio_request_vq(struct virtqueue *vq) +{ + struct virtio_gpio_line *line; + unsigned int len; + + do { + line = virtqueue_get_buf(vq, &len); + if (!line) + return; + + line->rxlen = len; + complete(&line->completion); + } while (1); +} + +static void virtio_gpio_free_vqs(struct virtio_device *vdev) +{ + vdev->config->reset(vdev); + vdev->config->del_vqs(vdev); +} + +static int virtio_gpio_alloc_vqs(struct virtio_gpio *vgpio, + struct virtio_device *vdev) +{ + const char * const names[] = { "requestq" }; + vq_callback_t *cbs[] = { + virtio_gpio_request_vq, + }; + struct virtqueue *vqs[1] = { NULL }; + int ret; + + ret = virtio_find_vqs(vdev, 1, vqs, cbs, names, NULL); + if (ret) { + dev_err(&vdev->dev, "failed to find vqs: %d\n", ret); + return ret; + } + + if (!vqs[0]) { + dev_err(&vdev->dev, "failed to find requestq vq\n"); + return -ENODEV; + } + vgpio->request_vq = vqs[0]; + + return 0; +} + +static const char **virtio_gpio_get_names(struct virtio_gpio *vgpio, + u32 gpio_names_size, u16 ngpio) +{ + struct virtio_gpio_response_get_names *res; + struct device *dev = &vgpio->vdev->dev; + u8 *gpio_names, *str; + const char **names; + int i, ret, len; + + if (!gpio_names_size) + return NULL; + + len = sizeof(*res) + gpio_names_size; + res = devm_kzalloc(dev, len, GFP_KERNEL); + if (!res) + return NULL; + gpio_names = res->value; + + ret = _virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_GET_NAMES, 0, 0, NULL, + res, len); + if (ret) { + dev_err(dev, "Failed to get GPIO names: %d\n", ret); + return NULL; + } + + names = devm_kcalloc(dev, ngpio, sizeof(*names), GFP_KERNEL); + if (!names) + return NULL; + + /* NULL terminate the string instead of checking it */ + gpio_names[gpio_names_size - 1] = '\0'; + + for (i = 0, str = gpio_names; i < ngpio; i++) { + names[i] = str; + str += strlen(str) + 1; /* zero-length strings are allowed */ + + if (str > gpio_names + gpio_names_size) { + dev_err(dev, "gpio_names block is too short (%d)\n", i); + return NULL; + } + } + + return names; +} + +static int virtio_gpio_probe(struct virtio_device *vdev) +{ + struct virtio_gpio_config config; + struct device *dev = &vdev->dev; + struct virtio_gpio *vgpio; + u32 gpio_names_size; + u16 ngpio; + int ret, i; + + vgpio = devm_kzalloc(dev, sizeof(*vgpio), GFP_KERNEL); + if (!vgpio) + return -ENOMEM; + + /* Read configuration */ + virtio_cread_bytes(vdev, 0, &config, sizeof(config)); + gpio_names_size = le32_to_cpu(config.gpio_names_size); + ngpio = le16_to_cpu(config.ngpio); + if (!ngpio) { + dev_err(dev, "Number of GPIOs can't be zero\n"); + return -EINVAL; + } + + vgpio->lines = devm_kcalloc(dev, ngpio, sizeof(*vgpio->lines), GFP_KERNEL); + if (!vgpio->lines) + return -ENOMEM; + + for (i = 0; i < ngpio; i++) { + mutex_init(&vgpio->lines[i].lock); + init_completion(&vgpio->lines[i].completion); + } + + mutex_init(&vgpio->lock); + vdev->priv = vgpio; + + vgpio->vdev = vdev; + vgpio->gc.free = virtio_gpio_free; + vgpio->gc.get_direction = virtio_gpio_get_direction; + vgpio->gc.direction_input = virtio_gpio_direction_input; + vgpio->gc.direction_output = virtio_gpio_direction_output; + vgpio->gc.get = virtio_gpio_get; + vgpio->gc.set = virtio_gpio_set; + vgpio->gc.ngpio = ngpio; + vgpio->gc.base = -1; /* Allocate base dynamically */ + vgpio->gc.label = dev_name(dev); + vgpio->gc.parent = dev; + vgpio->gc.owner = THIS_MODULE; + vgpio->gc.can_sleep = true; + + ret = virtio_gpio_alloc_vqs(vgpio, vdev); + if (ret) + return ret; + + /* Mark the device ready to perform operations from within probe() */ + virtio_device_ready(vdev); + + vgpio->gc.names = virtio_gpio_get_names(vgpio, gpio_names_size, ngpio); + + ret = gpiochip_add_data(&vgpio->gc, vgpio); + if (ret) { + virtio_gpio_free_vqs(vdev); + dev_err(dev, "Failed to add virtio-gpio controller\n"); + } + + return ret; +} + +static void virtio_gpio_remove(struct virtio_device *vdev) +{ + struct virtio_gpio *vgpio = vdev->priv; + + gpiochip_remove(&vgpio->gc); + virtio_gpio_free_vqs(vdev); +} + +static const struct virtio_device_id id_table[] = { + { VIRTIO_ID_GPIO, VIRTIO_DEV_ANY_ID }, + {}, +}; +MODULE_DEVICE_TABLE(virtio, id_table); + +static struct virtio_driver virtio_gpio_driver = { + .id_table = id_table, + .probe = virtio_gpio_probe, + .remove = virtio_gpio_remove, + .driver = { + .name = KBUILD_MODNAME, + .owner = THIS_MODULE, + }, +}; +module_virtio_driver(virtio_gpio_driver); + +MODULE_AUTHOR("Enrico Weigelt, metux IT consult <info@metux.net>"); +MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>"); +MODULE_DESCRIPTION("VirtIO GPIO driver"); +MODULE_LICENSE("GPL"); |