usb: gadget: storage: make FSG_NUM_BUFFERS variable size
FSG_NUM_BUFFERS is set to 2 as default. Usually 2 buffers are enough to establish a good buffering pipeline. The number may be increased in order to compensate a for bursty VFS behaviour. Here follows a description of system that may require more than 2 buffers. * CPU ondemand governor active * latency cost for wake up and/or frequency change * DMA for IO Use case description. * Data transfer from MMC via VFS to USB. * DMA shuffles data from MMC and to USB. * The CPU wakes up every now and then to pass data in and out from VFS, which cause the bursty VFS behaviour. Test set up * Running dd on the host reading from the mass storage device * cmdline: dd if=/dev/sdb of=/dev/null bs=4k count=$((256*100)) * Caches are dropped on the host and on the device before each run Measurements on a Snowball board with ondemand_governor active. FSG_NUM_BUFFERS 2 104857600 bytes (105 MB) copied, 5.62173 s, 18.7 MB/s 104857600 bytes (105 MB) copied, 5.61811 s, 18.7 MB/s 104857600 bytes (105 MB) copied, 5.57817 s, 18.8 MB/s FSG_NUM_BUFFERS 4 104857600 bytes (105 MB) copied, 5.26839 s, 19.9 MB/s 104857600 bytes (105 MB) copied, 5.2691 s, 19.9 MB/s 104857600 bytes (105 MB) copied, 5.2711 s, 19.9 MB/s There may not be one optimal number for all boards. This is why the number is added to Kconfig. If selecting USB_GADGET_DEBUG_FILES this value may be set by a module parameter as well. Signed-off-by: Per Forlin <per.forlin@linaro.org> Acked-by: Michal Nazarewicz <mina86@mina86.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Felipe Balbi <balbi@ti.com>
This commit is contained in:
Per Forlin
Felipe Balbi
Родитель
04eee25b1d
Коммит
6532c7fdb2
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@ -96,6 +96,22 @@ config USB_GADGET_VBUS_DRAW
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This value will be used except for system-specific gadget
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drivers that have more specific information.
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config USB_GADGET_STORAGE_NUM_BUFFERS
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int "Number of storage pipeline buffers"
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range 2 4
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default 2
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help
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Usually 2 buffers are enough to establish a good buffering
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pipeline. The number may be increased in order to compensate
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for a bursty VFS behaviour. For instance there may be CPU wake up
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latencies that makes the VFS to appear bursty in a system with
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an CPU on-demand governor. Especially if DMA is doing IO to
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offload the CPU. In this case the CPU will go into power
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save often and spin up occasionally to move data within VFS.
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If selecting USB_GADGET_DEBUG_FILES this value may be set by
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a module parameter as well.
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If unsure, say 2.
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#
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# USB Peripheral Controller Support
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#
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@ -362,7 +362,7 @@ struct fsg_common {
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struct fsg_buffhd *next_buffhd_to_fill;
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struct fsg_buffhd *next_buffhd_to_drain;
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struct fsg_buffhd buffhds[FSG_NUM_BUFFERS];
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struct fsg_buffhd *buffhds;
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int cmnd_size;
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u8 cmnd[MAX_COMMAND_SIZE];
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@ -2340,7 +2340,7 @@ reset:
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if (common->fsg) {
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fsg = common->fsg;
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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struct fsg_buffhd *bh = &common->buffhds[i];
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if (bh->inreq) {
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@ -2397,7 +2397,7 @@ reset:
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clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);
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/* Allocate the requests */
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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struct fsg_buffhd *bh = &common->buffhds[i];
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rc = alloc_request(common, fsg->bulk_in, &bh->inreq);
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@ -2466,7 +2466,7 @@ static void handle_exception(struct fsg_common *common)
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/* Cancel all the pending transfers */
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if (likely(common->fsg)) {
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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bh = &common->buffhds[i];
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if (bh->inreq_busy)
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usb_ep_dequeue(common->fsg->bulk_in, bh->inreq);
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@ -2478,7 +2478,7 @@ static void handle_exception(struct fsg_common *common)
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/* Wait until everything is idle */
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for (;;) {
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int num_active = 0;
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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bh = &common->buffhds[i];
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num_active += bh->inreq_busy + bh->outreq_busy;
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}
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@ -2501,7 +2501,7 @@ static void handle_exception(struct fsg_common *common)
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*/
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spin_lock_irq(&common->lock);
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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bh = &common->buffhds[i];
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bh->state = BUF_STATE_EMPTY;
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}
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@ -2710,6 +2710,10 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common,
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int nluns, i, rc;
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char *pathbuf;
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rc = fsg_num_buffers_validate();
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if (rc != 0)
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return ERR_PTR(rc);
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/* Find out how many LUNs there should be */
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nluns = cfg->nluns;
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if (nluns < 1 || nluns > FSG_MAX_LUNS) {
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@ -2728,6 +2732,14 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common,
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common->free_storage_on_release = 0;
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}
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common->buffhds = kcalloc(fsg_num_buffers,
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sizeof *(common->buffhds), GFP_KERNEL);
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if (!common->buffhds) {
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if (common->free_storage_on_release)
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kfree(common);
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return ERR_PTR(-ENOMEM);
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}
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common->ops = cfg->ops;
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common->private_data = cfg->private_data;
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@ -2805,7 +2817,7 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common,
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/* Data buffers cyclic list */
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bh = common->buffhds;
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i = FSG_NUM_BUFFERS;
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i = fsg_num_buffers;
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goto buffhds_first_it;
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do {
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bh->next = bh + 1;
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@ -2931,12 +2943,13 @@ static void fsg_common_release(struct kref *ref)
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{
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struct fsg_buffhd *bh = common->buffhds;
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unsigned i = FSG_NUM_BUFFERS;
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unsigned i = fsg_num_buffers;
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do {
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kfree(bh->buf);
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} while (++bh, --i);
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}
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kfree(common->buffhds);
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if (common->free_storage_on_release)
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kfree(common);
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}
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@ -460,7 +460,6 @@ struct fsg_dev {
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struct fsg_buffhd *next_buffhd_to_fill;
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struct fsg_buffhd *next_buffhd_to_drain;
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struct fsg_buffhd buffhds[FSG_NUM_BUFFERS];
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int thread_wakeup_needed;
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struct completion thread_notifier;
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@ -487,6 +486,8 @@ struct fsg_dev {
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unsigned int nluns;
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struct fsg_lun *luns;
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struct fsg_lun *curlun;
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/* Must be the last entry */
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struct fsg_buffhd buffhds[];
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};
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typedef void (*fsg_routine_t)(struct fsg_dev *);
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@ -2737,7 +2738,7 @@ static int do_set_interface(struct fsg_dev *fsg, int altsetting)
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reset:
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/* Deallocate the requests */
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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struct fsg_buffhd *bh = &fsg->buffhds[i];
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if (bh->inreq) {
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@ -2798,7 +2799,7 @@ reset:
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}
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/* Allocate the requests */
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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struct fsg_buffhd *bh = &fsg->buffhds[i];
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if ((rc = alloc_request(fsg, fsg->bulk_in, &bh->inreq)) != 0)
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@ -2894,7 +2895,7 @@ static void handle_exception(struct fsg_dev *fsg)
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/* Cancel all the pending transfers */
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if (fsg->intreq_busy)
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usb_ep_dequeue(fsg->intr_in, fsg->intreq);
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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bh = &fsg->buffhds[i];
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if (bh->inreq_busy)
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usb_ep_dequeue(fsg->bulk_in, bh->inreq);
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@ -2905,7 +2906,7 @@ static void handle_exception(struct fsg_dev *fsg)
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/* Wait until everything is idle */
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for (;;) {
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num_active = fsg->intreq_busy;
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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bh = &fsg->buffhds[i];
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num_active += bh->inreq_busy + bh->outreq_busy;
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}
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@ -2927,7 +2928,7 @@ static void handle_exception(struct fsg_dev *fsg)
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* state, and the exception. Then invoke the handler. */
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spin_lock_irq(&fsg->lock);
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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bh = &fsg->buffhds[i];
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bh->state = BUF_STATE_EMPTY;
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}
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@ -3157,7 +3158,7 @@ static void /* __init_or_exit */ fsg_unbind(struct usb_gadget *gadget)
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}
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/* Free the data buffers */
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for (i = 0; i < FSG_NUM_BUFFERS; ++i)
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for (i = 0; i < fsg_num_buffers; ++i)
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kfree(fsg->buffhds[i].buf);
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/* Free the request and buffer for endpoint 0 */
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@ -3445,7 +3446,7 @@ static int __init fsg_bind(struct usb_gadget *gadget)
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req->complete = ep0_complete;
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/* Allocate the data buffers */
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for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
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for (i = 0; i < fsg_num_buffers; ++i) {
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struct fsg_buffhd *bh = &fsg->buffhds[i];
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/* Allocate for the bulk-in endpoint. We assume that
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@ -3456,7 +3457,7 @@ static int __init fsg_bind(struct usb_gadget *gadget)
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goto out;
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bh->next = bh + 1;
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}
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fsg->buffhds[FSG_NUM_BUFFERS - 1].next = &fsg->buffhds[0];
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fsg->buffhds[fsg_num_buffers - 1].next = &fsg->buffhds[0];
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/* This should reflect the actual gadget power source */
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usb_gadget_set_selfpowered(gadget);
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@ -3572,7 +3573,9 @@ static int __init fsg_alloc(void)
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{
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struct fsg_dev *fsg;
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fsg = kzalloc(sizeof *fsg, GFP_KERNEL);
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fsg = kzalloc(sizeof *fsg +
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fsg_num_buffers * sizeof *(fsg->buffhds), GFP_KERNEL);
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if (!fsg)
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return -ENOMEM;
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spin_lock_init(&fsg->lock);
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@ -3590,6 +3593,10 @@ static int __init fsg_init(void)
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int rc;
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struct fsg_dev *fsg;
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rc = fsg_num_buffers_validate();
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if (rc != 0)
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return rc;
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if ((rc = fsg_alloc()) != 0)
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return rc;
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fsg = the_fsg;
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@ -52,6 +52,12 @@
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* characters rather then a pointer to void.
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*/
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/*
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* When USB_GADGET_DEBUG_FILES is defined the module param num_buffers
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* sets the number of pipeline buffers (length of the fsg_buffhd array).
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* The valid range of num_buffers is: num >= 2 && num <= 4.
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*/
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#include <linux/usb/storage.h>
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#include <scsi/scsi.h>
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@ -264,8 +270,31 @@ static struct fsg_lun *fsg_lun_from_dev(struct device *dev)
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#define EP0_BUFSIZE 256
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#define DELAYED_STATUS (EP0_BUFSIZE + 999) /* An impossibly large value */
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/* Number of buffers we will use. 2 is enough for double-buffering */
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#define FSG_NUM_BUFFERS 2
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#ifdef CONFIG_USB_GADGET_DEBUG_FILES
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static unsigned int fsg_num_buffers = CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS;
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module_param_named(num_buffers, fsg_num_buffers, uint, S_IRUGO);
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MODULE_PARM_DESC(num_buffers, "Number of pipeline buffers");
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#else
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/*
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* Number of buffers we will use.
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* 2 is usually enough for good buffering pipeline
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*/
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#define fsg_num_buffers CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS
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#endif /* CONFIG_USB_DEBUG */
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/* check if fsg_num_buffers is within a valid range */
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static inline int fsg_num_buffers_validate(void)
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{
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if (fsg_num_buffers >= 2 && fsg_num_buffers <= 4)
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return 0;
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pr_err("fsg_num_buffers %u is out of range (%d to %d)\n",
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fsg_num_buffers, 2 ,4);
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return -EINVAL;
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}
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/* Default size of buffer length. */
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#define FSG_BUFLEN ((u32)16384)
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