linux/include
Stephen Boyd a098ecd2fa firmware: support loading into a pre-allocated buffer
Some systems are memory constrained but they need to load very large
firmwares.  The firmware subsystem allows drivers to request this
firmware be loaded from the filesystem, but this requires that the
entire firmware be loaded into kernel memory first before it's provided
to the driver.  This can lead to a situation where we map the firmware
twice, once to load the firmware into kernel memory and once to copy the
firmware into the final resting place.

This creates needless memory pressure and delays loading because we have
to copy from kernel memory to somewhere else.  Let's add a
request_firmware_into_buf() API that allows drivers to request firmware
be loaded directly into a pre-allocated buffer.  This skips the
intermediate step of allocating a buffer in kernel memory to hold the
firmware image while it's read from the filesystem.  It also requires
that drivers know how much memory they'll require before requesting the
firmware and negates any benefits of firmware caching because the
firmware layer doesn't manage the buffer lifetime.

For a 16MB buffer, about half the time is spent performing a memcpy from
the buffer to the final resting place.  I see loading times go from
0.081171 seconds to 0.047696 seconds after applying this patch.  Plus
the vmalloc pressure is reduced.

This is based on a patch from Vikram Mulukutla on codeaurora.org:
  https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.18/commit/drivers/base/firmware_class.c?h=rel/msm-3.18&id=0a328c5f6cd999f5c591f172216835636f39bcb5

Link: http://lkml.kernel.org/r/20160607164741.31849-4-stephen.boyd@linaro.org
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Vikram Mulukutla <markivx@codeaurora.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02 19:35:10 -04:00
..
acpi treewide: replace obsolete _refok by __ref 2016-08-02 17:31:41 -04:00
asm-generic Merge branch 'akpm' (patches from Andrew) 2016-07-26 19:55:54 -07:00
clocksource
crypto A number of improvements for the /dev/random driver; the most 2016-07-27 15:11:55 -07:00
drm drm/ttm: partial revert "cleanup ttm_tt_(unbind|destroy)" v3 2016-07-29 14:37:04 -04:00
dt-bindings ARM: DT updates for v4.8 2016-08-01 18:37:45 -04:00
keys
kvm
linux firmware: support loading into a pre-allocated buffer 2016-08-02 19:35:10 -04:00
math-emu
media [media] doc-rst: add some needed escape codes 2016-07-23 08:05:02 -03:00
memory
misc cxl: Add cxl_check_and_switch_mode() API to switch bi-modal cards 2016-07-14 20:28:11 +10:00
net treewide: replace obsolete _refok by __ref 2016-08-02 17:31:41 -04:00
pcmcia
ras tracing, RAS: Cleanup on __get_str() usage 2016-07-15 15:51:16 -04:00
rdma
rxrpc
scsi fcoe: implement FIP VLAN responder 2016-07-20 19:49:41 -04:00
soc ARM: SoC driver updates for v4.8 2016-08-01 18:36:01 -04:00
sound Merge tag 'drm-for-v4.8' of git://people.freedesktop.org/~airlied/linux 2016-08-01 21:44:08 -04:00
target
trace Merge branch 'for-linus-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2016-07-31 21:27:32 -04:00
uapi uapi: move forward declarations of internal structures 2016-08-02 17:31:41 -04:00
video gpu: ipu-v3: ipu-dmfc: Use static DMFC FIFO allocation mechanism 2016-07-12 18:23:43 +02:00
xen xen: add static initialization of steal_clock op to xen_time_ops 2016-07-26 14:07:06 +01:00
Kbuild