[PATCH 30/39] i2400m/USB: read transactions from the USB device

Inaky Perez-Gonzalez
2008-11-26T22:41:41Z

This code implements reading from the USB device; it uses a simple
adaptive algorithm so it doesn't preallocate huge buffers that then
are underused. When a transaction is read, it is passed to the generic
driver for processing and delivery.

All is done in a kthread sitting on a loop. We need a thread context
to run USB autopm functions and to process the received data (can get
to be heavy in processing time). It is dedicated to a single task, so
it has less overhead than a workqueue.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
---
drivers/net/wimax/i2400m/usb-rx.c | 417 +++++++++++++++++++++++++++++++++++++
1 files changed, 417 insertions(+), 0 deletions(-)
create mode 100644 drivers/net/wimax/i2400m/usb-rx.c

diff --git a/drivers/net/wimax/i2400m/usb-rx.c b/drivers/net/wimax/i2400m/usb-rx.c
new file mode 100644
index 0000000..074cc1f
--- /dev/null
+++ b/drivers/net/wimax/i2400m/usb-rx.c
@@ -0,0 +1,417 @@
+/*
+ * Intel Wireless WiMAX Connection 2400m
+ * USB RX handling
+ *
+ *
+ * Copyright (C) 2007-2008 Intel Corporation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Intel Corporation nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *
+ * Intel Corporation <linux-wimax@intel.com>
+ * Yanir Lubetkin <yanirx.lubetkin@intel.com>
+ * - Initial implementation
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
+ * - Use skb_clone(), break up processing in chunks
+ * - Split transport/device specific
+ * - Make buffer size dynamic to exert less memory pressure
+ *
+ *
+ * This handles the RX path on USB.
+ *
+ * When a notification is received that says 'there is RX data ready',
+ * we call i2400mu_rx_kick(); that wakes up the RX kthread, which
+ * reads a buffer from USB and passes it to i2400m_rx() in the generic
+ * handling code. The RX buffer has an specific format that is
+ * described in rx.c.
+ *
+ * We use a kernel thread in a loop because:
+ *
+ * - we want to be able to call the USB power management get/put
+ * functions (blocking) before each transaction.
+ *
+ * - We might get a lot of notifications and we don't want to submit
+ * a zillion reads; by serializing, we are throttling.
+ *
+ * - RX data processing can get heavy enough so that it is not
+ * appropiate for doing it in the USB callback; thus we run it in a
+ * process context.
+ *
+ * We provide a read buffer of an arbitrary size (short of a page); if
+ * the callback reports -EOVERFLOW, it means it was too small, so we
+ * just double the size and retry (being careful to append, as
+ * sometimes the device provided some data). Every now and then we
+ * check if the average packet size is smaller than the current packet
+ * size and if so, we halve it. At the end, the size of the
+ * preallocated buffer should be following the average received
+ * transaction size, adapting dynamically to it.
+ *
+ * ROADMAP
+ *
+ * i2400mu_rx_kick() Called from notif.c when we get a
+ * 'data ready' notification
+ * i2400mu_rxd() Kernel RX daemon
+ * i2400mu_rx() Receive USB data
+ * i2400m_rx() Send data to generic i2400m RX handling
+ *
+ * i2400mu_rx_setup() called from i2400mu_bus_dev_start()
+ *
+ * i2400mu_rx_release() called from i2400mu_bus_dev_stop()
+ */
+#include <linux/workqueue.h>
+#include <linux/usb.h>
+#include "i2400m-usb.h"
+
+
+#define D_SUBMODULE rx
+#include "usb-debug-levels.h"
+
+/*
+ * Dynamic RX size
+ *
+ * We can't let the rx_size be a multiple of 512 bytes (the RX
+ * endpoint's max packet size). On some USB host controllers (we
+ * haven't been able to fully characterize which), if the device is
+ * about to send (for example) X bytes and we only post a buffer to
+ * receive n*512, it will fail to mark that as babble (so that
+ * i2400mu_rx() [case -EOVERFLOW] can resize the buffer and get the
+ * rest).
+ *
+ * So on growing or shrinking, if it is a multiple of the
+ * maxpacketsize, we remove some (instead of incresing some, so in a
+ * buddy allocator we try to waste less space).
+ *
+ * Note we also need a hook for this on i2400mu_rx() -- when we do the
+ * first read, we are sure we won't hit this spot because
+ * i240mm->rx_size has been set properly. However, if we have to
+ * double because of -EOVERFLOW, when we launch the read to get the
+ * rest of the data, we *have* to make sure that also is not a
+ * multiple of the max_pkt_size.
+ */
+
+static
+size_t i2400mu_rx_size_grow(struct i2400mu *i2400mu)
+{
+ struct device *dev = &i2400mu->usb_iface->dev;
+ size_t rx_size;
+ const size_t max_pkt_size = 512;
+
+ rx_size = 2 * i2400mu->rx_size;
+ if (rx_size % max_pkt_size == 0) {
+ rx_size -= 8;
+ d_printf(1, dev,
+ "RX: expected size grew to %zu [adjusted -8] "
+ "from %zu\n",
+ rx_size, i2400mu->rx_size);
+ } else
+ d_printf(1, dev,
+ "RX: expected size grew to %zu from %zu\n",
+ rx_size, i2400mu->rx_size);
+ return rx_size;
+}
+
+
+static
+void i2400mu_rx_size_maybe_shrink(struct i2400mu *i2400mu)
+{
+ const size_t max_pkt_size = 512;
+ struct device *dev = &i2400mu->usb_iface->dev;
+
+ if (unlikely(i2400mu->rx_size_cnt >= 100
+ && i2400mu->rx_size_auto_shrink)) {
+ size_t avg_rx_size =
+ i2400mu->rx_size_acc / i2400mu->rx_size_cnt;
+ size_t new_rx_size = i2400mu->rx_size / 2;
+ if (avg_rx_size < new_rx_size) {
+ if (new_rx_size % max_pkt_size == 0) {
+ new_rx_size -= 8;
+ d_printf(1, dev,
+ "RX: expected size shrank to %zu "
+ "[adjusted -8] from %zu\n",
+ new_rx_size, i2400mu->rx_size);
+ } else
+ d_printf(1, dev,
+ "RX: expected size shrank to %zu "
+ "from %zu\n",
+ new_rx_size, i2400mu->rx_size);
+ i2400mu->rx_size = new_rx_size;
+ i2400mu->rx_size_cnt = 0;
+ i2400mu->rx_size_acc = i2400mu->rx_size;
+ }
+ }
+}
+
+/*
+ * Receive a message with payloads from the USB bus into an skb
+ *
+ * @i2400mu: USB device descriptor
+ * @rx_skb: skb where to place the received message
+ *
+ * Deals with all the USB-specifics of receiving, dynamically
+ * increasing the buffer size if so needed. Returns the payload in the
+ * skb, ready to process. On a zero-length packet, we retry.
+ *
+ * On soft USB errors, we retry (until they become too frequent and
+ * then are promoted to hard); on hard USB errors, we reset the
+ * device. On other errors (skb realloacation, we just drop it and
+ * hope for the next invocation to solve it).
+ *
+ * Returns: pointer to the skb if ok, ERR_PTR on error.
+ * NOTE: this function might realloc the skb (if it is too small),
+ * so always update with the one returned.
+ * ERR_PTR() is < 0 on error.
+ */
+static
+struct sk_buff *i2400mu_rx(struct i2400mu *i2400mu, struct sk_buff *rx_skb)
+{
+ int result = 0;
+ struct device *dev = &i2400mu->usb_iface->dev;
+ int usb_pipe, read_size, rx_size, do_autopm;
+ struct usb_endpoint_descriptor *epd;
+ const size_t max_pkt_size = 512;
+
+ d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
+ do_autopm = atomic_read(&i2400mu->do_autopm);
+ result = do_autopm ?
+ usb_autopm_get_interface(i2400mu->usb_iface) : 0;
+ if (result < 0) {
+ dev_err(dev, "RX: can't get autopm: %d\n", result);
+ do_autopm = 0;
+ }
+ epd = usb_get_epd(i2400mu->usb_iface, I2400MU_EP_BULK_IN);
+ usb_pipe = usb_rcvbulkpipe(i2400mu->usb_dev, epd->bEndpointAddress);
+retry:
+ rx_size = skb_end_pointer(rx_skb) - rx_skb->data - rx_skb->len;
+ if (unlikely(rx_size % max_pkt_size == 0)) {
+ rx_size -= 8;
+ d_printf(1, dev, "RX: rx_size adapted to %d [-8]\n", rx_size);
+ }
+ result = usb_bulk_msg(
+ i2400mu->usb_dev, usb_pipe, rx_skb->data + rx_skb->len,
+ rx_size, &read_size, HZ);
+ usb_mark_last_busy(i2400mu->usb_dev);
+ switch (result) {
+ case 0:
+ if (read_size == 0)
+ goto retry; /* ZLP, just resubmit */
+ skb_put(rx_skb, read_size);
+ break;
+ case -EINVAL: /* while removing driver */
+ case -ENODEV: /* dev disconnect ... */
+ case -ENOENT: /* just ignore it */
+ case -ESHUTDOWN:
+ case -ECONNRESET:
+ break;
+ case -EOVERFLOW: { /* too small, reallocate */
+ struct sk_buff *new_skb;
+ rx_size = i2400mu_rx_size_grow(i2400mu);
+ if (rx_size <= (1 << 16)) /* cap it */
+ i2400mu->rx_size = rx_size;
+ else if (printk_ratelimit()) {
+ dev_err(dev, "BUG? rx_size up to %d\n", rx_size);
+ result = -EINVAL;
+ goto out;
+ }
+ skb_put(rx_skb, read_size);
+ new_skb = skb_copy_expand(rx_skb, 0, rx_size - rx_skb->len,
+ GFP_KERNEL);
+ if (new_skb == NULL) {
+ if (printk_ratelimit())
+ dev_err(dev, "RX: Can't reallocate skb to %d; "
+ "RX dropped\n", rx_size);
+ kfree(rx_skb);
+ result = 0;
+ goto out; /* drop it...*/
+ }
+ kfree_skb(rx_skb);
+ rx_skb = new_skb;
+ i2400mu->rx_size_cnt = 0;
+ i2400mu->rx_size_acc = i2400mu->rx_size;
+ d_printf(1, dev, "RX: size changed to %d, received %d, "
+ "copied %d, capacity %ld\n",
+ rx_size, read_size, rx_skb->len,
+ (long) (skb_end_pointer(new_skb) - new_skb->head));
+ goto retry;
+ }
+ /* In most cases, it happens due to the hardware scheduling a
+ * read when there was no data - unfortunately, we have no way
+ * to tell this timeout from a USB timeout. So we just ignore
+ * it. */
+ case -ETIMEDOUT:
+ dev_err(dev, "RX: timeout: %d\n", result);
+ result = 0;
+ break;
+ default: /* Any error */
+ if (edc_inc(&i2400mu->urb_edc,
+ EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME))
+ goto error_reset;
+ dev_err(dev, "RX: error receiving URB: %d, retrying\n", result);
+ goto retry;
+ }
+out:
+ if (do_autopm)
+ usb_autopm_put_interface(i2400mu->usb_iface);
+ d_fnend(4, dev, "(i2400mu %p) = %p\n", i2400mu, rx_skb);
+ return rx_skb;
+
+error_reset:
+ dev_err(dev, "RX: maximum errors in URB exceeded; "
+ "resetting device\n");
+ usb_queue_reset_device(i2400mu->usb_iface);
+ rx_skb = ERR_PTR(result);
+ goto out;
+}
+
+
+/*
+ * Kernel thread for USB reception of data
+ *
+ * This thread waits for a kick; once kicked, it will allocate an skb
+ * and receive a single message to it from USB (using
+ * i2400mu_rx()). Once received, it is passed to the generic i2400m RX
+ * code for processing.
+ *
+ * When done processing, it runs some dirty statistics to verify if
+ * the last 100 messages received were smaller than half of the
+ * current RX buffer size. In that case, the RX buffer size is
+ * halved. This will helps lowering the pressure on the memory
+ * allocator.
+ *
+ * Hard errors force the thread to exit.
+ */
+static
+int i2400mu_rxd(void *_i2400mu)
+{
+ int result = 0;
+ struct i2400mu *i2400mu = _i2400mu;
+ struct i2400m *i2400m = &i2400mu->i2400m;
+ struct device *dev = &i2400mu->usb_iface->dev;
+ struct net_device *net_dev = i2400m->wimax_dev.net_dev;
+ size_t pending;
+ int rx_size;
+ struct sk_buff *rx_skb;
+
+ d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
+ while (1) {
+ d_printf(2, dev, "TX: waiting for messages\n");
+ pending = 0;
+ wait_event_interruptible(
+ i2400mu->rx_wq,
+ (kthread_should_stop() /* check this first! */
+ || (pending = atomic_read(&i2400mu->rx_pending_count)))
+ );
+ if (kthread_should_stop())
+ break;
+ if (pending == 0)
+ continue;
+ rx_size = i2400mu->rx_size;
+ d_printf(2, dev, "RX: reading up to %d bytes\n", rx_size);
+ rx_skb = __netdev_alloc_skb(net_dev, rx_size, GFP_KERNEL);
+ if (rx_skb == NULL) {
+ dev_err(dev, "RX: can't allocate skb [%d bytes]\n",
+ rx_size);
+ msleep(50); /* give it some time? */
+ continue;
+ }
+
+ /* Receive the message with the payloads */
+ rx_skb = i2400mu_rx(i2400mu, rx_skb);
+ result = PTR_ERR(rx_skb);
+ if (IS_ERR(rx_skb))
+ goto out;
+ atomic_dec(&i2400mu->rx_pending_count);
+ if (rx_skb->len == 0) { /* some ignorable condition */
+ kfree_skb(rx_skb);
+ continue;
+ }
+
+ /* Deliver the message to the generic i2400m code */
+ i2400mu->rx_size_cnt++;
+ i2400mu->rx_size_acc += rx_skb->len;
+ result = i2400m_rx(i2400m, rx_skb);
+ if (result == -EIO
+ && edc_inc(&i2400mu->urb_edc,
+ EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME)) {
+ goto error_reset;
+ }
+
+ /* Maybe adjust RX buffer size */
+ i2400mu_rx_size_maybe_shrink(i2400mu);
+ }
+ result = 0;
+out:
+ d_fnend(4, dev, "(i2400mu %p) = %d\n", i2400mu, result);
+ return result;
+
+error_reset:
+ dev_err(dev, "RX: maximum errors in received buffer exceeded; "
+ "resetting device\n");
+ usb_queue_reset_device(i2400mu->usb_iface);
+ goto out;
+}
+
+
+/*
+ * Start reading from the device
+ *
+ * @i2400m: device instance
+ *
+ * Notify the RX thread that there is data pending.
+ */
+void i2400mu_rx_kick(struct i2400mu *i2400mu)
+{
+ struct i2400m *i2400m = &i2400mu->i2400m;
+ struct device *dev = &i2400mu->usb_iface->dev;
+
+ d_fnstart(3, dev, "(i2400mu %p)\n", i2400m);
+ atomic_inc(&i2400mu->rx_pending_count);
+ wake_up_all(&i2400mu->rx_wq);
+ d_fnend(3, dev, "(i2400m %p) = void\n", i2400m);
+}
+
+
+int i2400mu_rx_setup(struct i2400mu *i2400mu)
+{
+ int result = 0;
+ struct i2400m *i2400m = &i2400mu->i2400m;
+ struct device *dev = &i2400mu->usb_iface->dev;
+ struct wimax_dev *wimax_dev = &i2400m->wimax_dev;
+
+ i2400mu->rx_kthread = kthread_run(i2400mu_rxd, i2400mu, "%s-rx",
+ wimax_dev->name);
+ if (IS_ERR(i2400mu->rx_kthread)) {
+ result = PTR_ERR(i2400mu->rx_kthread);
+ dev_err(dev, "RX: cannot start thread: %d\n", result);
+ }
+ return result;
+}
+
+void i2400mu_rx_release(struct i2400mu *i2400mu)
+{
+ kthread_stop(i2400mu->rx_kthread);
+}
+
--
1.5.6.5