linux-stable/drivers
Linus Walleij c3dccb74be mmc: core: Delete bounce buffer Kconfig option
This option is activated by all multiplatform configs and what
not so we almost always have it turned on, and the memory it
saves is negligible, even more so moving forward. The actual
bounce buffer only gets allocated only when used, the only
thing the ifdefs are saving is a little bit of code.

It is highly improper to have this as a Kconfig option that
get turned on by Kconfig, make this a pure runtime-thing and
let the host decide whether we use bounce buffers. We add a
new property "disable_bounce" to the host struct.

Notice that mmc_queue_calc_bouncesz() already disables the
bounce buffers if host->max_segs != 1, so any arch that has a
maximum number of segments higher than 1 will have bounce
buffers disabled.

The option CONFIG_MMC_BLOCK_BOUNCE is default y so the
majority of platforms in the kernel already have it on, and
it then gets turned off at runtime since most of these have
a host->max_segs > 1. The few exceptions that have
host->max_segs == 1 and still turn off the bounce buffering
are those that disable it in their defconfig.

Those are the following:

arch/arm/configs/colibri_pxa300_defconfig
arch/arm/configs/zeus_defconfig
- Uses MMC_PXA, drivers/mmc/host/pxamci.c
- Sets host->max_segs = NR_SG, which is 1
- This needs its bounce buffer deactivated so we set
  host->disable_bounce to true in the host driver

arch/arm/configs/davinci_all_defconfig
- Uses MMC_DAVINCI, drivers/mmc/host/davinci_mmc.c
- This driver sets host->max_segs to MAX_NR_SG, which is 16
- That means this driver anyways disabled bounce buffers
- No special action needed for this platform

arch/arm/configs/lpc32xx_defconfig
arch/arm/configs/nhk8815_defconfig
arch/arm/configs/u300_defconfig
- Uses MMC_ARMMMCI, drivers/mmc/host/mmci.[c|h]
- This driver by default sets host->max_segs to NR_SG,
  which is 128, unless a DMA engine is used, and in that case
  the number of segments are also > 1
- That means this driver already disables bounce buffers
- No special action needed for these platforms

arch/arm/configs/sama5_defconfig
- Uses MMC_SDHCI, MMC_SDHCI_PLTFM, MMC_SDHCI_OF_AT91, MMC_ATMELMCI
- Uses drivers/mmc/host/sdhci.c
- Normally sets host->max_segs to SDHCI_MAX_SEGS which is 128 and
  thus disables bounce buffers
- Sets host->max_segs to 1 if SDHCI_USE_SDMA is set
- SDHCI_USE_SDMA is only set by SDHCI on PCI adapers
- That means that for this platform bounce buffers are already
  disabled at runtime
- No special action needed for this platform

arch/blackfin/configs/CM-BF533_defconfig
arch/blackfin/configs/CM-BF537E_defconfig
- Uses MMC_SPI (a simple MMC card connected on SPI pins)
- Uses drivers/mmc/host/mmc_spi.c
- Sets host->max_segs to MMC_SPI_BLOCKSATONCE which is 128
- That means this platform already disables bounce buffers at
  runtime
- No special action needed for these platforms

arch/mips/configs/cavium_octeon_defconfig
- Uses MMC_CAVIUM_OCTEON, drivers/mmc/host/cavium.c
- Sets host->max_segs to 16 or 1
- Setting host->disable_bounce to be sure for the 1 case

arch/mips/configs/qi_lb60_defconfig
- Uses MMC_JZ4740, drivers/mmc/host/jz4740_mmc.c
- This sets host->max_segs to 128 so bounce buffers are
  already runtime disabled
- No action needed for this platform

It would be interesting to come up with a list of the platforms
that actually end up using bounce buffers. I have not been
able to infer such a list, but it occurs when
host->max_segs == 1 and the bounce buffering is not explicitly
disabled.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
2017-06-20 10:30:17 +02:00
..
accessibility
acpi Merge branch 'acpica-fixes' 2017-06-15 01:52:32 +02:00
amba
android
ata
atm
auxdisplay
base Merge branches 'intel_pstate' and 'pm-sleep' 2017-06-09 01:25:16 +02:00
bcma
block Fix loop device flush before configure v3 2017-06-08 08:04:18 -06:00
bluetooth
bus
cdrom
char Improve performance by using a lockless update mechanism suggested by 2017-06-11 12:02:01 -07:00
clk
clocksource
connector
cpufreq Merge branches 'pm-cpufreq', 'pm-cpuidle' and 'pm-devfreq' 2017-06-15 01:51:33 +02:00
cpuidle Merge branches 'pm-cpufreq', 'pm-cpuidle' and 'pm-devfreq' 2017-06-15 01:51:33 +02:00
crypto
dax device-dax: fix 'dax' device filesystem inode destruction crash 2017-06-09 08:50:49 -07:00
dca
devfreq PM / devfreq: exynos-ppmu: Staticize event list 2017-06-12 10:12:07 +09:00
dio
dma dmaengine: pl330: fix warning in pl330_remove 2017-06-02 11:49:44 +05:30
dma-buf
edac
eisa
extcon
firewire
firmware Merge branch 'dmi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging 2017-06-16 17:13:06 +09:00
fmc
fpga
fsi
gpio gpio: mvebu: fix gpio bank registration when pwm is used 2017-06-09 09:38:27 +02:00
gpu Merge tag 'drm-intel-fixes-2017-06-15' of git://anongit.freedesktop.org/git/drm-intel into drm-fixes 2017-06-16 10:01:52 +10:00
hid HID: let generic driver yield control iff specific driver has been enabled 2017-06-13 16:52:50 +02:00
hsi hsi: Fix build regression due to netdev destructor fix. 2017-06-08 10:16:05 -04:00
hv
hwmon hwmon: (aspeed-pwm-tacho) make fan/pwm names start with index 1 2017-06-03 03:55:43 -07:00
hwspinlock
hwtracing
i2c i2c: ismt: fix wrong device address when unmap the data buffer 2017-06-15 16:07:03 +02:00
ide
idle
iio iio: buffer-dmaengine: Add missing header buffer_impl.h 2017-06-13 20:56:05 +01:00
infiniband Fixes #2 for 4.12-rc 2017-06-16 17:38:23 +09:00
input Input: synaptics-rmi4 - register F03 port as pass-through serio 2017-06-09 09:57:19 -07:00
iommu
ipack
irqchip Xtensa fixes for v4.12-rc6 2017-06-13 15:09:10 +09:00
isdn
leds LED fixes for 4.12-rc6 2017-06-18 08:51:35 +09:00
lguest
lightnvm
macintosh
mailbox
mcb
md md: initialise ->writes_pending in personality modules. 2017-06-05 16:04:35 -07:00
media media fixes for v4.12-rc6 2017-06-15 17:37:40 +09:00
memory Merge tag 'at91-4.12-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux into fixes 2017-06-01 17:07:31 -07:00
memstick
message
mfd
misc Char/Misc driver fixes for 4.12-rc5 2017-06-11 11:29:15 -07:00
mmc mmc: core: Delete bounce buffer Kconfig option 2017-06-20 10:30:17 +02:00
mtd
net i40e: Fix a sleep-in-atomic bug 2017-06-14 23:45:22 -04:00
nfc
ntb
nubus
nvdimm
nvme nvme: relax APST default max latency to 100ms 2017-06-07 11:08:55 +02:00
nvmem
of
oprofile
parisc
parport
pci PCI: endpoint: Select CRC32 to fix test build error 2017-06-12 15:46:13 -05:00
pcmcia
perf
phy
pinctrl
platform platform-drivers-x86 for v4.12-2 2017-06-16 17:30:44 +09:00
pnp
power
powercap
pps
ps3
ptp
pwm
rapidio
ras
regulator
remoteproc
reset
rpmsg
rtc
s390 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-06-15 18:09:47 +09:00
sbus
scsi SCSI fixes on 20170610 2017-06-11 11:21:08 -07:00
sfi
sh
sn
soc
spi
spmi
ssb
staging Staging/IIO fixes for 4.12-rc6 2017-06-18 08:36:30 +09:00
target
tc
tee
thermal
thunderbolt
tty Revert "tty: fix port buffer locking" 2017-06-04 10:23:25 +02:00
uio
usb USB fixes for 4.12-rc6 2017-06-18 08:39:54 +09:00
uwb
vfio
vhost
video video: fbdev: udlfb: drop log level for blanking 2017-06-14 12:40:36 +02:00
virt
virtio virtio_balloon: disable VIOMMU support 2017-06-18 23:13:35 +03:00
vlynq
vme
w1
watchdog
xen xen: fix for 4.12 rc5 2017-06-09 09:59:51 -07:00
zorro
Kconfig
Makefile