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673e7bbdb3
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U. Artie Eoff 673e7bbdb3 drm/i915: intel_backlight scale() math WA 
Improper truncated integer division in the scale() function causes
actual_brightness != brightness. This (partial) work-around should be
sufficient for a majority of use-cases, but it is by no means a complete
solution.

TODO: Determine how best to scale "user" values to "hw" values, and
vice-versa, when the ranges are of different sizes. That would be a
buggy scenario even with this work-around.

The issue was introduced in the following (v3.17-rc1) commit:

    6dda730 drm/i915: respect the VBT minimum backlight brightness

Note that for easier backporting this commit adds a duplicated macro.
A follow-up cleanup patch rectifies this for 3.18+

v2: (thanks to Chris Wilson) clarify commit message, use rounded division
macro

v3: -DIV_ROUND_CLOSEST() fails to build with CONFIG_X86_32=y. (Jani)
    -Use DIV_ROUND_CLOSEST_ULL() instead. (Damien)
    -v1 and v2 originally authored by Joe Konno.

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
Cc: stable@vger.kernel.org
Reviewed-By: Joe Konno <joe.konno@intel.com>
[danvet: Add backporting note.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-10-06 16:47:24 +02:00
..
accessibility
acpi Merge branches 'acpi-rtc', 'acpi-lpss' and 'acpi-battery' 2014-09-11 15:09:30 +02:00
amba
ata ahci_xgene: Fix the link down in first attempt for the APM X-Gene SoC AHCI SATA host controller driver. 2014-09-06 11:27:15 +09:00
atm Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-08-13 18:27:40 -06:00
auxdisplay
base Merge remote-tracking branches 'regmap/fix/cache', 'regmap/fix/debugfs' and 'regmap/fix/volatile' into regmap-linus 2014-08-31 13:23:45 +01:00
bcma bcma: add PCI ID for spromless BCM43217 2014-08-25 15:39:23 -04:00
block Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2014-09-13 09:39:55 -07:00
bluetooth Bluetooth: Fix crash in the Marvell driver initialization codepath 2014-07-31 01:07:28 +02:00
bus bus: arm-ccn: Move event cleanup routine 2014-09-05 13:25:01 -07:00
cdrom
char virtio: rng: add derating factor for use by hwrng core 2014-08-15 10:26:01 +05:30
clk ARM: SoC platform changes for 3.17 2014-08-08 11:14:29 -07:00
clocksource ARM: SoC platform changes for 3.17 2014-08-08 11:14:29 -07:00
connector connector: Use ktime_get_ns() 2014-07-23 10:18:07 -07:00
cpufreq cpufreq / OPP: Fix the order of arguments for kcalloc() 2014-09-08 00:02:58 +02:00
cpuidle ARM: 8130/1: cpuidle/cpuidle-big_little: fix reading cpu id part number 2014-08-27 15:40:45 +01:00
crypto PCI changes for the v3.17 merge window (part 2): 2014-08-14 18:10:33 -06:00
dca
devfreq PM / OPP: Remove ARCH_HAS_OPP 2014-07-23 00:51:30 +02:00
dio
dma dmaengine: jz4740: Fix non-cyclic descriptor completion 2014-09-11 10:54:25 +05:30
dma-buf dma-buf/fence: Fix a kerneldoc warning 2014-08-28 11:59:09 +05:30
edac Merge branch 'linux_next' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-edac 2014-08-15 17:56:45 -06:00
eisa
extcon extcon: sm5502: Change internal hardware switch according to cable type 2014-07-23 10:22:35 +09:00
firewire Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-08-06 09:38:14 -07:00
firmware firmware: Do not use WARN_ON(!spin_is_locked()) 2014-08-22 08:45:40 +01:00
fmc
gpio gpio: bt8xx: fix release of managed resources 2014-08-29 14:31:43 +02:00
gpu drm/i915: intel_backlight scale() math WA 2014-10-06 16:47:24 +02:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid 2014-08-27 09:38:06 -07:00
hsi HSI changes for the v3.17 series 2014-08-06 20:06:14 -07:00
hv Char / Misc driver patches for 3.17-rc1 2014-08-04 17:32:24 -07:00
hwmon hwmon: (ds1621) Update zbits after conversion rate change 2014-08-28 11:18:47 -07:00
hwspinlock hwspinlock: enable OMAP build for AM33xx, AM43xx & DRA7xx 2014-07-29 11:46:28 +03:00
i2c Revert "i2c: rcar: remove spinlock" 2014-09-04 19:59:42 +02:00
ide ide: use module_platform_driver() 2014-08-05 21:16:46 -07:00
idle intel_idle: Broadwell support 2014-08-15 17:06:40 -04:00
iio Staging driver patches for 3.17-rc1 2014-08-04 18:36:12 -07:00
infiniband mlx4: Set user-space raw Ethernet QPs to properly handle VXLAN traffic 2014-08-29 20:13:00 -07:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2014-09-11 10:08:36 -07:00
iommu iommu/fsl: Fix warning resulting from adding PCI device twice 2014-09-05 16:01:46 +02:00
ipack
irqchip irqchip: gic-v3: Declare rdist as __percpu pointer to __iomem pointer 2014-09-03 12:08:10 +00:00
isdn drivers: isdn: eicon: xdi_msg.h: Fix typo in #ifndef 2014-08-22 11:31:30 -07:00
leds Revert "leds: convert blink timer to workqueue" 2014-09-02 10:02:13 -07:00
lguest mm/vmalloc.c: clean up map_vm_area third argument 2014-08-06 18:01:19 -07:00
macintosh == Changes to existing drivers == 2014-08-07 17:23:16 -07:00
mailbox mailbox/omap: add a parent structure for every IP instance 2014-07-29 01:57:25 -07:00
mcb
md dm cache: fix race causing dirty blocks to be marked as clean 2014-09-10 11:20:47 -04:00
media media: use pci_zalloc_consistent 2014-08-08 15:57:28 -07:00
memory memory: Freescale CoreNet Coherency Fabric error reporting driver 2014-07-29 19:26:30 -05:00
memstick
message mptfusion: tweak null pointer checks 2014-07-25 17:16:58 -04:00
mfd mfd: twl4030-power: Fix PM idle pin configuration to not conflict with regulators 2014-08-28 15:57:55 +01:00
misc Lattice ECP3 FPGA: Check firmware pointer 2014-09-08 14:38:14 -07:00
mmc PCI changes for the v3.17 merge window (part 2): 2014-08-14 18:10:33 -06:00
mtd Two trivial MTD updates for 3.17-rc4: 2014-09-06 12:12:09 -07:00
net Merge tag 'master-2014-09-04' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless 2014-09-07 16:11:10 -07:00
nfc NFC: st21nfca: Adding P2P support to st21nfca in Initiator & Target mode 2014-07-23 01:14:41 +02:00
ntb ntb: Add alignment check to meet hardware requirement 2014-09-14 00:10:38 -04:00
nubus
of of/irq: Fix lookup to use 'interrupts-extended' property first 2014-08-16 09:03:58 +01:00
oprofile
parisc parisc: dino: fix %d confusingly prefixed with 0x in format string 2014-08-27 14:35:04 +02:00
parport drivers/parport/parport_ip32.c: use PTR_ERR_OR_ZERO 2014-08-08 15:57:25 -07:00
pci PCI update for v3.17: 2014-09-03 08:45:48 -07:00
pcmcia Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2014-08-07 08:50:34 -07:00
phy phy: miphy365x: Select GENERIC_PHY instead of depending on it 2014-08-28 11:17:43 +05:30
pinctrl pinctrl: baytrail: resolve unbalanced IRQ wake disable warning 2014-09-10 14:25:51 +02:00
platform toshiba_acpi: fix and cleanup toshiba_kbd_bl_mode_store() 2014-09-03 10:45:12 -07:00
pnp ACPI / PNP: Fix acpi_pnp_match() 2014-07-30 00:23:09 +02:00
power ARM: SoC platform changes for 3.17 2014-08-08 11:14:29 -07:00
powercap powercap / RAPL: change domain detection message 2014-09-03 01:29:00 +02:00
pps
ps3
ptp PCI: Remove DEFINE_PCI_DEVICE_TABLE macro use 2014-08-12 12:15:14 -06:00
pwm pwm: Fix period and polarity in pwm_get() for non-perfect matches 2014-08-18 10:58:43 +02:00
rapidio PCI: Remove DEFINE_PCI_DEVICE_TABLE macro use 2014-08-12 12:15:14 -06:00
ras
regulator == Changes to existing drivers == 2014-08-07 17:17:39 -07:00
remoteproc
reset
rpmsg
rtc drivers/rtc/rtc-s5m.c: re-add support for devices without irq specified 2014-08-29 16:28:16 -07:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-09-08 08:27:00 -07:00
sbus Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2014-08-05 18:57:18 -07:00
scsi Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2014-08-29 11:21:49 -07:00
sfi
sh sh: intc: Confine SH_INTC to platforms that need it 2014-08-22 12:28:16 +09:00
sn
soc
spi Merge remote-tracking branch 'spi/fix/sh-msiof' into spi-linus 2014-08-31 13:46:19 +01:00
spmi
ssb ssb: add PCI ID 0x4351 2014-08-25 15:39:22 -04:00
staging Linux 3.17-rc5 2014-09-16 11:38:04 +10:00
target SCSI misc on 20140806 2014-08-06 20:10:32 -07:00
tc
thermal Merge branches 'exynos-fix', 'for-rc', 'int3403-fix', 'misc', 'rcar-thermal' and 'sti-thermal' of .git into next 2014-07-22 10:13:00 +08:00
thunderbolt thunderbolt: Clear hops before overwriting 2014-08-26 14:54:48 -07:00
tty tty: xuartps: Fix tx_emtpy() callback 2014-09-08 16:33:56 -07:00
uio
usb usb: fixes for v3.17-rc4 2014-09-11 15:08:14 -07:00
uwb uwb: init beacon cache entry before registering uwb device 2014-09-08 16:03:21 -07:00
vfio drivers/vfio: Enable VFIO if EEH is not supported 2014-08-08 10:39:16 -06:00
vhost
video Linux 3.17-rc5 2014-09-16 11:38:04 +10:00
virt
virtio virtio: Replace DEFINE_PCI_DEVICE_TABLE macro use 2014-07-27 21:07:15 +09:30
vlynq
vme vme: bridges: use pci_zalloc_consistent 2014-08-08 15:57:30 -07:00
w1
watchdog Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
xen xen: bug fixes for 3.17-rc4 2014-09-11 16:52:29 -07:00
zorro
Kconfig Char / Misc driver patches for 3.17-rc1 2014-08-04 17:32:24 -07:00
Makefile Driver core patches for 3.17-rc1 2014-08-04 18:34:04 -07:00