diff options
| author | Per Forlin <per.forlin@linaro.org> | 2011-08-19 21:21:27 +0200 |
|---|---|---|
| committer | Felipe Balbi <balbi@ti.com> | 2011-09-09 13:06:04 +0300 |
| commit | 6532c7fdb2c3a2ec1b949ecd2ff5375069c1639a (patch) | |
| tree | 26afd8fdff7923f818f49aa405bb4208d1da914e /drivers/usb/gadget/f_mass_storage.c | |
| parent | 04eee25b1d754a837360504b7af426d1f86ffeb7 (diff) | |
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>
Diffstat (limited to 'drivers/usb/gadget/f_mass_storage.c')
| -rw-r--r-- | drivers/usb/gadget/f_mass_storage.c | 29 |
1 files changed, 21 insertions, 8 deletions
diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c index 4306a833948..75694147314 100644 --- a/drivers/usb/gadget/f_mass_storage.c +++ b/drivers/usb/gadget/f_mass_storage.c @@ -362,7 +362,7 @@ struct fsg_common { 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 @@ reset: 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 @@ reset: 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 @@ static void handle_exception(struct fsg_common *common) /* 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 @@ static void handle_exception(struct fsg_common *common) /* 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 @@ static void handle_exception(struct fsg_common *common) */ 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 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common, 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 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common, 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 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common, /* 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 @@ static void fsg_common_release(struct kref *ref) { 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); } |