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>
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index fe56379..a60b472 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -96,6 +96,22 @@
This value will be used except for system-specific gadget
drivers that have more specific information.
+config USB_GADGET_STORAGE_NUM_BUFFERS
+ int "Number of storage pipeline buffers"
+ range 2 4
+ default 2
+ help
+ Usually 2 buffers are enough to establish a good buffering
+ pipeline. The number may be increased in order to compensate
+ for a bursty VFS behaviour. For instance there may be CPU wake up
+ latencies that makes the VFS to appear bursty in a system with
+ an CPU on-demand governor. Especially if DMA is doing IO to
+ offload the CPU. In this case the CPU will go into power
+ save often and spin up occasionally to move data within VFS.
+ If selecting USB_GADGET_DEBUG_FILES this value may be set by
+ a module parameter as well.
+ If unsure, say 2.
+
#
# USB Peripheral Controller Support
#
diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 4306a83..7569414 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -362,7 +362,7 @@
struct fsg_buffhd *next_buffhd_to_fill;
struct fsg_buffhd *next_buffhd_to_drain;
- struct fsg_buffhd buffhds[FSG_NUM_BUFFERS];
+ struct fsg_buffhd *buffhds;
int cmnd_size;
u8 cmnd[MAX_COMMAND_SIZE];
@@ -2340,7 +2340,7 @@
if (common->fsg) {
fsg = common->fsg;
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
struct fsg_buffhd *bh = &common->buffhds[i];
if (bh->inreq) {
@@ -2397,7 +2397,7 @@
clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);
/* Allocate the requests */
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
struct fsg_buffhd *bh = &common->buffhds[i];
rc = alloc_request(common, fsg->bulk_in, &bh->inreq);
@@ -2466,7 +2466,7 @@
/* Cancel all the pending transfers */
if (likely(common->fsg)) {
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
bh = &common->buffhds[i];
if (bh->inreq_busy)
usb_ep_dequeue(common->fsg->bulk_in, bh->inreq);
@@ -2478,7 +2478,7 @@
/* Wait until everything is idle */
for (;;) {
int num_active = 0;
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
bh = &common->buffhds[i];
num_active += bh->inreq_busy + bh->outreq_busy;
}
@@ -2501,7 +2501,7 @@
*/
spin_lock_irq(&common->lock);
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
bh = &common->buffhds[i];
bh->state = BUF_STATE_EMPTY;
}
@@ -2710,6 +2710,10 @@
int nluns, i, rc;
char *pathbuf;
+ rc = fsg_num_buffers_validate();
+ if (rc != 0)
+ return ERR_PTR(rc);
+
/* Find out how many LUNs there should be */
nluns = cfg->nluns;
if (nluns < 1 || nluns > FSG_MAX_LUNS) {
@@ -2728,6 +2732,14 @@
common->free_storage_on_release = 0;
}
+ common->buffhds = kcalloc(fsg_num_buffers,
+ sizeof *(common->buffhds), GFP_KERNEL);
+ if (!common->buffhds) {
+ if (common->free_storage_on_release)
+ kfree(common);
+ return ERR_PTR(-ENOMEM);
+ }
+
common->ops = cfg->ops;
common->private_data = cfg->private_data;
@@ -2805,7 +2817,7 @@
/* Data buffers cyclic list */
bh = common->buffhds;
- i = FSG_NUM_BUFFERS;
+ i = fsg_num_buffers;
goto buffhds_first_it;
do {
bh->next = bh + 1;
@@ -2931,12 +2943,13 @@
{
struct fsg_buffhd *bh = common->buffhds;
- unsigned i = FSG_NUM_BUFFERS;
+ unsigned i = fsg_num_buffers;
do {
kfree(bh->buf);
} while (++bh, --i);
}
+ kfree(common->buffhds);
if (common->free_storage_on_release)
kfree(common);
}
diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index c6f96a2..4b9797d 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -460,7 +460,6 @@
struct fsg_buffhd *next_buffhd_to_fill;
struct fsg_buffhd *next_buffhd_to_drain;
- struct fsg_buffhd buffhds[FSG_NUM_BUFFERS];
int thread_wakeup_needed;
struct completion thread_notifier;
@@ -487,6 +486,8 @@
unsigned int nluns;
struct fsg_lun *luns;
struct fsg_lun *curlun;
+ /* Must be the last entry */
+ struct fsg_buffhd buffhds[];
};
typedef void (*fsg_routine_t)(struct fsg_dev *);
@@ -2737,7 +2738,7 @@
reset:
/* Deallocate the requests */
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
struct fsg_buffhd *bh = &fsg->buffhds[i];
if (bh->inreq) {
@@ -2798,7 +2799,7 @@
}
/* Allocate the requests */
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
struct fsg_buffhd *bh = &fsg->buffhds[i];
if ((rc = alloc_request(fsg, fsg->bulk_in, &bh->inreq)) != 0)
@@ -2894,7 +2895,7 @@
/* Cancel all the pending transfers */
if (fsg->intreq_busy)
usb_ep_dequeue(fsg->intr_in, fsg->intreq);
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
bh = &fsg->buffhds[i];
if (bh->inreq_busy)
usb_ep_dequeue(fsg->bulk_in, bh->inreq);
@@ -2905,7 +2906,7 @@
/* Wait until everything is idle */
for (;;) {
num_active = fsg->intreq_busy;
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
bh = &fsg->buffhds[i];
num_active += bh->inreq_busy + bh->outreq_busy;
}
@@ -2927,7 +2928,7 @@
* state, and the exception. Then invoke the handler. */
spin_lock_irq(&fsg->lock);
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
bh = &fsg->buffhds[i];
bh->state = BUF_STATE_EMPTY;
}
@@ -3157,7 +3158,7 @@
}
/* Free the data buffers */
- for (i = 0; i < FSG_NUM_BUFFERS; ++i)
+ for (i = 0; i < fsg_num_buffers; ++i)
kfree(fsg->buffhds[i].buf);
/* Free the request and buffer for endpoint 0 */
@@ -3445,7 +3446,7 @@
req->complete = ep0_complete;
/* Allocate the data buffers */
- for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
+ for (i = 0; i < fsg_num_buffers; ++i) {
struct fsg_buffhd *bh = &fsg->buffhds[i];
/* Allocate for the bulk-in endpoint. We assume that
@@ -3456,7 +3457,7 @@
goto out;
bh->next = bh + 1;
}
- fsg->buffhds[FSG_NUM_BUFFERS - 1].next = &fsg->buffhds[0];
+ fsg->buffhds[fsg_num_buffers - 1].next = &fsg->buffhds[0];
/* This should reflect the actual gadget power source */
usb_gadget_set_selfpowered(gadget);
@@ -3572,7 +3573,9 @@
{
struct fsg_dev *fsg;
- fsg = kzalloc(sizeof *fsg, GFP_KERNEL);
+ fsg = kzalloc(sizeof *fsg +
+ fsg_num_buffers * sizeof *(fsg->buffhds), GFP_KERNEL);
+
if (!fsg)
return -ENOMEM;
spin_lock_init(&fsg->lock);
@@ -3590,6 +3593,10 @@
int rc;
struct fsg_dev *fsg;
+ rc = fsg_num_buffers_validate();
+ if (rc != 0)
+ return rc;
+
if ((rc = fsg_alloc()) != 0)
return rc;
fsg = the_fsg;
diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
index 3ea70d8..9fd3799 100644
--- a/drivers/usb/gadget/storage_common.c
+++ b/drivers/usb/gadget/storage_common.c
@@ -52,6 +52,12 @@
* characters rather then a pointer to void.
*/
+/*
+ * When USB_GADGET_DEBUG_FILES is defined the module param num_buffers
+ * sets the number of pipeline buffers (length of the fsg_buffhd array).
+ * The valid range of num_buffers is: num >= 2 && num <= 4.
+ */
+
#include <linux/usb/storage.h>
#include <scsi/scsi.h>
@@ -264,8 +270,31 @@
#define EP0_BUFSIZE 256
#define DELAYED_STATUS (EP0_BUFSIZE + 999) /* An impossibly large value */
-/* Number of buffers we will use. 2 is enough for double-buffering */
-#define FSG_NUM_BUFFERS 2
+#ifdef CONFIG_USB_GADGET_DEBUG_FILES
+
+static unsigned int fsg_num_buffers = CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS;
+module_param_named(num_buffers, fsg_num_buffers, uint, S_IRUGO);
+MODULE_PARM_DESC(num_buffers, "Number of pipeline buffers");
+
+#else
+
+/*
+ * Number of buffers we will use.
+ * 2 is usually enough for good buffering pipeline
+ */
+#define fsg_num_buffers CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS
+
+#endif /* CONFIG_USB_DEBUG */
+
+/* check if fsg_num_buffers is within a valid range */
+static inline int fsg_num_buffers_validate(void)
+{
+ if (fsg_num_buffers >= 2 && fsg_num_buffers <= 4)
+ return 0;
+ pr_err("fsg_num_buffers %u is out of range (%d to %d)\n",
+ fsg_num_buffers, 2 ,4);
+ return -EINVAL;
+}
/* Default size of buffer length. */
#define FSG_BUFLEN ((u32)16384)