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Subject[PATCHv9 2/2] virtio_console: Add support for remoteproc serial
Date
Add a simple serial connection driver called
VIRTIO_ID_RPROC_SERIAL (11) for communicating with a
remote processor in an asymmetric multi-processing
configuration.

This implementation reuses the existing virtio_console
implementation, and adds support for DMA allocation
of data buffers and disables use of tty console and
the virtio control queue.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
---
drivers/char/virtio_console.c | 192 ++++++++++++++++++++++++++++++++++-----
include/uapi/linux/virtio_ids.h | 1 +
2 files changed, 170 insertions(+), 23 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 5482246..55a89a4 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -37,8 +37,12 @@
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/module.h>
+#include <linux/dma-mapping.h>
+#include <linux/kconfig.h>
#include "../tty/hvc/hvc_console.h"

+#define is_rproc_enabled IS_ENABLED(CONFIG_REMOTEPROC)
+
/*
* This is a global struct for storing common data for all the devices
* this driver handles.
@@ -112,6 +116,15 @@ struct port_buffer {
/* offset in the buf from which to consume data */
size_t offset;

+ /* DMA address of buffer */
+ dma_addr_t dma;
+
+ /* Device we got DMA memory from */
+ struct device *dev;
+
+ /* List of pending dma buffers to free */
+ struct list_head list;
+
/* If sgpages == 0 then buf is used */
unsigned int sgpages;

@@ -331,6 +344,11 @@ static bool is_console_port(struct port *port)
return false;
}

+static bool is_rproc_serial(const struct virtio_device *vdev)
+{
+ return is_rproc_enabled && vdev->id.device == VIRTIO_ID_RPROC_SERIAL;
+}
+
static inline bool use_multiport(struct ports_device *portdev)
{
/*
@@ -342,11 +360,13 @@ static inline bool use_multiport(struct ports_device *portdev)
return portdev->vdev->features[0] & (1 << VIRTIO_CONSOLE_F_MULTIPORT);
}

-static void free_buf(struct port_buffer *buf)
+static DEFINE_SPINLOCK(dma_bufs_lock);
+static LIST_HEAD(pending_free_dma_bufs);
+
+static void free_buf(struct port_buffer *buf, bool can_sleep)
{
unsigned int i;

- kfree(buf->buf);
for (i = 0; i < buf->sgpages; i++) {
struct page *page = sg_page(&buf->sg[i]);
if (!page)
@@ -354,14 +374,57 @@ static void free_buf(struct port_buffer *buf)
put_page(page);
}

+ if (!buf->dev) {
+ kfree(buf->buf);
+ } else if (is_rproc_enabled) {
+ unsigned long flags;
+
+ /* dma_free_coherent requires interrupts to be enabled. */
+ if (!can_sleep) {
+ /* queue up dma-buffers to be freed later */
+ spin_lock_irqsave(&dma_bufs_lock, flags);
+ list_add_tail(&buf->list, &pending_free_dma_bufs);
+ spin_unlock_irqrestore(&dma_bufs_lock, flags);
+ return;
+ }
+ dma_free_coherent(buf->dev, buf->size, buf->buf, buf->dma);
+
+ /* Release device refcnt and allow it to be freed */
+ put_device(buf->dev);
+ }
+
kfree(buf);
}

+static void reclaim_dma_bufs(void)
+{
+ unsigned long flags;
+ struct port_buffer *buf, *tmp;
+ LIST_HEAD(tmp_list);
+
+ if (list_empty(&pending_free_dma_bufs))
+ return;
+
+ /* Create a copy of the pending_free_dma_bufs while holding the lock */
+ spin_lock_irqsave(&dma_bufs_lock, flags);
+ list_cut_position(&tmp_list, &pending_free_dma_bufs,
+ pending_free_dma_bufs.prev);
+ spin_unlock_irqrestore(&dma_bufs_lock, flags);
+
+ /* Release the dma buffers, without irqs enabled */
+ list_for_each_entry_safe(buf, tmp, &tmp_list, list) {
+ list_del(&buf->list);
+ free_buf(buf, true);
+ }
+}
+
static struct port_buffer *alloc_buf(struct virtqueue *vq, size_t buf_size,
int pages)
{
struct port_buffer *buf;

+ reclaim_dma_bufs();
+
/*
* Allocate buffer and the sg list. The sg list array is allocated
* directly after the port_buffer struct.
@@ -373,11 +436,34 @@ static struct port_buffer *alloc_buf(struct virtqueue *vq, size_t buf_size,

buf->sgpages = pages;
if (pages > 0) {
+ buf->dev = NULL;
buf->buf = NULL;
return buf;
}

- buf->buf = kmalloc(buf_size, GFP_KERNEL);
+ if (is_rproc_serial(vq->vdev)) {
+ /*
+ * Allocate DMA memory from ancestor. When a virtio
+ * device is created by remoteproc, the DMA memory is
+ * associated with the grandparent device:
+ * vdev => rproc => platform-dev.
+ * The code here would have been less quirky if
+ * DMA_MEMORY_INCLUDES_CHILDREN had been supported
+ * in dma-coherent.c
+ */
+ if (!vq->vdev->dev.parent || !vq->vdev->dev.parent->parent)
+ goto free_buf;
+ buf->dev = vq->vdev->dev.parent->parent;
+
+ /* Increase device refcnt to avoid freeing it */
+ get_device(buf->dev);
+ buf->buf = dma_alloc_coherent(buf->dev, buf_size, &buf->dma,
+ GFP_KERNEL);
+ } else {
+ buf->dev = NULL;
+ buf->buf = kmalloc(buf_size, GFP_KERNEL);
+ }
+
if (!buf->buf)
goto free_buf;
buf->len = 0;
@@ -446,7 +532,7 @@ static void discard_port_data(struct port *port)
port->stats.bytes_discarded += buf->len - buf->offset;
if (add_inbuf(port->in_vq, buf) < 0) {
err++;
- free_buf(buf);
+ free_buf(buf, false);
}
port->inbuf = NULL;
buf = get_inbuf(port);
@@ -518,7 +604,7 @@ static void reclaim_consumed_buffers(struct port *port)
return;
}
while ((buf = virtqueue_get_buf(port->out_vq, &len))) {
- free_buf(buf);
+ free_buf(buf, false);
port->outvq_full = false;
}
}
@@ -765,7 +851,7 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
goto out;

free_buf:
- free_buf(buf);
+ free_buf(buf, true);
out:
return ret;
}
@@ -839,6 +925,15 @@ static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
.u.data = &sgl,
};

+ /*
+ * Rproc_serial does not yet support splice. To support splice
+ * pipe_to_sg() must allocate dma-buffers and copy content from
+ * regular pages to dma pages. And alloc_buf and free_buf must
+ * support allocating and freeing such a list of dma-buffers.
+ */
+ if (is_rproc_serial(port->out_vq->vdev))
+ return -EINVAL;
+
ret = wait_port_writable(port, filp->f_flags & O_NONBLOCK);
if (ret < 0)
return ret;
@@ -857,7 +952,7 @@ static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
ret = __send_to_port(port, buf->sg, sgl.n, sgl.len, buf, true);

if (unlikely(ret <= 0))
- kfree(sgl.sg);
+ free_buf(buf, true);
return ret;
}

@@ -906,6 +1001,7 @@ static int port_fops_release(struct inode *inode, struct file *filp)
reclaim_consumed_buffers(port);
spin_unlock_irq(&port->outvq_lock);

+ reclaim_dma_bufs();
/*
* Locks aren't necessary here as a port can't be opened after
* unplug, and if a port isn't unplugged, a kref would already
@@ -1057,7 +1153,10 @@ static void resize_console(struct port *port)
return;

vdev = port->portdev->vdev;
- if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE))
+
+ /* Don't test F_SIZE at all if we're rproc: not a valid feature! */
+ if (!is_rproc_serial(vdev) &&
+ virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE))
hvc_resize(port->cons.hvc, port->cons.ws);
}

@@ -1249,7 +1348,7 @@ static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
ret = add_inbuf(vq, buf);
if (ret < 0) {
spin_unlock_irq(lock);
- free_buf(buf);
+ free_buf(buf, true);
break;
}
nr_added_bufs++;
@@ -1337,10 +1436,18 @@ static int add_port(struct ports_device *portdev, u32 id)
goto free_device;
}

- /*
- * If we're not using multiport support, this has to be a console port
- */
- if (!use_multiport(port->portdev)) {
+ if (is_rproc_serial(port->portdev->vdev))
+ /*
+ * For rproc_serial assume remote processor is connected.
+ * rproc_serial does not want the console port, only
+ * the generic port implementation.
+ */
+ port->host_connected = true;
+ else if (!use_multiport(port->portdev)) {
+ /*
+ * If we're not using multiport support,
+ * this has to be a console port.
+ */
err = init_port_console(port);
if (err)
goto free_inbufs;
@@ -1373,7 +1480,7 @@ static int add_port(struct ports_device *portdev, u32 id)

free_inbufs:
while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
- free_buf(buf);
+ free_buf(buf, true);
free_device:
device_destroy(pdrvdata.class, port->dev->devt);
free_cdev:
@@ -1415,11 +1522,11 @@ static void remove_port_data(struct port *port)

/* Remove buffers we queued up for the Host to send us data in. */
while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
- free_buf(buf);
+ free_buf(buf, true);

/* Free pending buffers from the out-queue. */
while ((buf = virtqueue_detach_unused_buf(port->out_vq)))
- free_buf(buf);
+ free_buf(buf, true);
}

/*
@@ -1621,7 +1728,7 @@ static void control_work_handler(struct work_struct *work)
if (add_inbuf(portdev->c_ivq, buf) < 0) {
dev_warn(&portdev->vdev->dev,
"Error adding buffer to queue\n");
- free_buf(buf);
+ free_buf(buf, false);
}
}
spin_unlock(&portdev->cvq_lock);
@@ -1817,10 +1924,10 @@ static void remove_controlq_data(struct ports_device *portdev)
return;

while ((buf = virtqueue_get_buf(portdev->c_ivq, &len)))
- free_buf(buf);
+ free_buf(buf, true);

while ((buf = virtqueue_detach_unused_buf(portdev->c_ivq)))
- free_buf(buf);
+ free_buf(buf, true);
}

/*
@@ -1867,11 +1974,15 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)

multiport = false;
portdev->config.max_nr_ports = 1;
- if (virtio_config_val(vdev, VIRTIO_CONSOLE_F_MULTIPORT,
- offsetof(struct virtio_console_config,
- max_nr_ports),
- &portdev->config.max_nr_ports) == 0)
+
+ /* Don't test MULTIPORT at all if we're rproc: not a valid feature! */
+ if (!is_rproc_serial(vdev) &&
+ virtio_config_val(vdev, VIRTIO_CONSOLE_F_MULTIPORT,
+ offsetof(struct virtio_console_config,
+ max_nr_ports),
+ &portdev->config.max_nr_ports) == 0) {
multiport = true;
+ }

err = init_vqs(portdev);
if (err < 0) {
@@ -1981,6 +2092,16 @@ static unsigned int features[] = {
VIRTIO_CONSOLE_F_MULTIPORT,
};

+static struct virtio_device_id rproc_serial_id_table[] = {
+#if IS_ENABLED(CONFIG_REMOTEPROC)
+ { VIRTIO_ID_RPROC_SERIAL, VIRTIO_DEV_ANY_ID },
+#endif
+ { 0 },
+};
+
+static unsigned int rproc_serial_features[] = {
+};
+
#ifdef CONFIG_PM
static int virtcons_freeze(struct virtio_device *vdev)
{
@@ -2065,6 +2186,20 @@ static struct virtio_driver virtio_console = {
#endif
};

+/*
+ * virtio_rproc_serial refers to __devinit function which causes
+ * section mismatch warnings. So use __refdata to silence warnings.
+ */
+static struct virtio_driver __refdata virtio_rproc_serial = {
+ .feature_table = rproc_serial_features,
+ .feature_table_size = ARRAY_SIZE(rproc_serial_features),
+ .driver.name = "virtio_rproc_serial",
+ .driver.owner = THIS_MODULE,
+ .id_table = rproc_serial_id_table,
+ .probe = virtcons_probe,
+ .remove = virtcons_remove,
+};
+
static int __init init(void)
{
int err;
@@ -2089,7 +2224,15 @@ static int __init init(void)
pr_err("Error %d registering virtio driver\n", err);
goto free;
}
+ err = register_virtio_driver(&virtio_rproc_serial);
+ if (err < 0) {
+ pr_err("Error %d registering virtio rproc serial driver\n",
+ err);
+ goto unregister;
+ }
return 0;
+unregister:
+ unregister_virtio_driver(&virtio_console);
free:
if (pdrvdata.debugfs_dir)
debugfs_remove_recursive(pdrvdata.debugfs_dir);
@@ -2099,7 +2242,10 @@ free:

static void __exit fini(void)
{
+ reclaim_dma_bufs();
+
unregister_virtio_driver(&virtio_console);
+ unregister_virtio_driver(&virtio_rproc_serial);

class_destroy(pdrvdata.class);
if (pdrvdata.debugfs_dir)
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 270fb22..a7630d0 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -37,5 +37,6 @@
#define VIRTIO_ID_RPMSG 7 /* virtio remote processor messaging */
#define VIRTIO_ID_SCSI 8 /* virtio scsi */
#define VIRTIO_ID_9P 9 /* 9p virtio console */
+#define VIRTIO_ID_RPROC_SERIAL 11 /* virtio remoteproc serial link */

#endif /* _LINUX_VIRTIO_IDS_H */
--
1.7.5.4
--
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