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/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;