The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is (mostly) ignored
and this typically results in resource leaks. To improve here there is a
quest to make the remove callback return void. In the first step of this
quest all drivers are converted to .remove_new() which already returns
void.
Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230308073945.2336302-11-u.kleine-koenig@pengutronix.de
Most but not all PWMs drive the PWM pin to its inactive state when
disabled. However if there is no enable_gpio and no regulator the PWM
must drive the inactive state to actually disable the backlight.
So keep the PWM on in this case.
Note that to determine if there is a regulator some effort is required
because it might happen that there isn't actually one but the regulator
core gave us a dummy. (A nice side effect is that this makes the
regulator actually optional even on fully constrained systems.)
This fixes backlight disabling e.g. on i.MX6 when an inverted PWM is
used.
Hint for the future: If this change results in a regression, the bug is
in the lowlevel PWM driver.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230120120018.161103-3-u.kleine-koenig@pengutronix.de
When the function pwm_backlight_update_status() was called with
brightness > 0, pwm_get_state() was called twice (once directly and once
in compute_duty_cycle). Also pwm_apply_state() was called twice (once in
pwm_backlight_power_on() and once directly).
Optimize this to do both calls only once.
Note that with this affects the order of regulator and PWM setup. It's
not expected to have a relevant effect on hardware. The rationale for
this is that the regulator (and the GPIO) are reasonable to switch in
pwm_backlight_power_on()/pwm_backlight_power_off() but the PWM has
nothing to do with power. (The post_pwm_on_delay and pwm_off_delay are
still there though.)
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230120120018.161103-2-u.kleine-koenig@pengutronix.de
There is no in-tree user left which relies on legacy probing. So drop
support for it which removes another user of the deprecated
pwm_request() function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221117072151.3789691-1-u.kleine-koenig@pengutronix.de
kmalloc_array()/kcalloc() should be used to avoid potential overflow when
a multiplication is needed to compute the size of the requested memory.
So turn a kzalloc()+explicit size computation into an equivalent kcalloc().
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/bd3d74acfa58d59f6f5f81fc5a9fb409edb8d747.1644046817.git.christophe.jaillet@wanadoo.fr
Currently there are (at least) two problems in the way pwm_bl starts
managing the enable_gpio pin. Both occur when the backlight is initially
off and the driver finds the pin not already in output mode and, as a
result, unconditionally switches it to output-mode and asserts the signal.
Problem 1: This could cause the backlight to flicker since, at this stage
in driver initialisation, we have no idea what the PWM and regulator are
doing (an unconfigured PWM could easily "rest" at 100% duty cycle).
Problem 2: This will cause us not to correctly honour the
post_pwm_on_delay (which also risks flickers).
Fix this by moving the code to configure the GPIO output mode until after
we have examines the handover state. That allows us to initialize
enable_gpio to off if the backlight is currently off and on if the
backlight is on.
Cc: stable@vger.kernel.org
Reported-by: Marek Vasut <marex@denx.de>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Marek Vasut <marex@denx.de>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
The previous behavior was a little unexpected, its properties/problems:
1. It was designed to generate strictly increasing values (no repeats)
2. It had quantization errors when calculating step size. Resulting in
unexpected jumps near the end of some segments.
Example settings:
brightness-levels = <0 1 2 4 8 16 32 64 128 256>;
num-interpolated-steps = <16>;
Whenever num-interpolated-steps was larger than the distance
between 2 consecutive brightness levels the table would get really
discontinuous. The slope of the interpolation would stick with
integers only and if it was 0 the whole line segment would get skipped.
The distances between 1 2 4 and 8 would be 1 (property #1 fighting us),
and only starting with 16 it would start to interpolate properly.
Property #1 is not enough. The goal here is more than just monotonically
increasing. We should still care about the shape of the curve. Repeated
points might be desired if we're in the part of the curve where we want
to go slow (aka slope near 0).
Problem #2 is plainly a bug. Imagine if the 64 entry was 63 instead,
the calculated slope on the 32-63 segment will be almost half as it
should be.
The most expected and simplest algorithm for interpolation is linear
interpolation, which would handle both problems.
Let's just implement that!
Take pairs of points from the brightness-levels array and linearly
interpolate between them. On the X axis (what userspace sees) we'll
now have equally sized intervals (num-interpolated-steps sized,
as opposed to before where we were at the mercy of quantization).
Signed-off-by: Alexandru Stan <amstan@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
The majority of this batch is conversion of the PWM period and duty
cycle to 64-bit unsigned integers, which is required so that some types
of hardware can generate the full range of signals that they're capable
of. The remainder is mostly minor fixes and cleanups.
-----BEGIN PGP SIGNATURE-----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=v6MG
-----END PGP SIGNATURE-----
Merge tag 'pwm/for-5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm
Pull pwm updates from Thierry Reding:
"The majority of this batch is conversion of the PWM period and duty
cycle to 64-bit unsigned integers, which is required so that some
types of hardware can generate the full range of signals that they're
capable of.
The remainder is mostly minor fixes and cleanups"
* tag 'pwm/for-5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm:
pwm: bcm-iproc: handle clk_get_rate() return
pwm: Replace HTTP links with HTTPS ones
pwm: omap-dmtimer: Repair pwm_omap_dmtimer_chip's broken kerneldoc header
pwm: mediatek: Provide missing kerneldoc description for 'soc' arg
pwm: bcm-kona: Remove impossible comparison when validating duty cycle
pwm: bcm-iproc: Remove impossible comparison when validating duty cycle
pwm: iqs620a: Use lowercase hexadecimal literals for consistency
pwm: Convert period and duty cycle to u64
clk: pwm: Use 64-bit division function
backlight: pwm_bl: Use 64-bit division function
pwm: sun4i: Use nsecs_to_jiffies to avoid a division
pwm: sifive: Use 64-bit division macro
pwm: iqs620a: Use 64-bit division
pwm: imx27: Use 64-bit division macro
pwm: imx-tpm: Use 64-bit division macro
pwm: clps711x: Use 64-bit division macro
hwmon: pwm-fan: Use 64-bit division macro
drm/i915: Use 64-bit division macro
Introduce the backlight_get_brightness() helper in all
video/backlight/* drivers. This simplifies the code and align the
implementation of the update_status() operation across the different
backlight drivers.
Some of the drivers gains a little extra functionality by the change
as they now respect the fb_blank() ioctl.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Since the PWM framework is switching struct pwm_state.period's datatype
to u64, prepare for this transition by using div_u64 to handle a 64-bit
dividend instead of a straight division operation.
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
The PWM backlight still supports passing a enable GPIO line as
platform data using the legacy <linux/gpio.h> API.
It turns out that ever board using this mechanism except one
is pass .enable_gpio = -1. So we drop all these cargo-culted -1's
from all instances of this platform data in the kernel.
The remaning board, Palm TC, is converted to pass a machine
descriptior table with the "enable" GPIO instead, and delete the
platform data entry for enable_gpio and the code handling it
and things should work smoothly with the new API.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Using a power-of-2 instead of power-of-10 base makes the computations
much cheaper. 2^16 is safe; retval never becomes more than 2^48 +
2^32/2. On a 32 bit platform, the very expensive 64/32 division at the
end of cie1931() instead becomes essentially free (a shift by 32 is
just a register rename).
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
For a fixed small exponent of 3, it is more efficient to simply use
two explicit multiplications rather than calling the int_pow() library
function: Aside from the function call overhead, its implementation
using repeated squaring means it ends up doing four 64x64
multiplications.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
lightness*1000 is nowhere near overflowing 32 bits, so we can just use
an ordinary 32/32 division, which is much cheaper than the 64/32 done
via do_div().
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
The "break-even" point for the two formulas is L==8, which is also
what the code actually implements. [Incidentally, at that point one
has Y=0.008856, not 0.08856].
Moreover, all the sources I can find say the linear factor is 903.3
rather than 902.3, which makes sense since then the formulas agree at
L==8, both yielding the 0.008856 figure to four significant digits.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Add curly braces to an 'else' branch in pwm_backlight_update_status()
to match the corresponding 'if' branch.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
pwm_backlight_probe() re-assigns pb->levels for every brightness
level. This is not needed and was likely not intended, since
neither side of the assignment changes during the loop. Assign
the field only once.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Check if a brightness curve specified in the device tree is linear or
not and set the corresponding property accordingly. This makes the
scale type available to userspace via the 'scale' sysfs attribute.
To determine if a curve is linear it is compared to a interpolated linear
curve between min and max brightness. The curve is considered linear if
no value deviates more than +/-5% of ${brightness_range} from their
interpolated value.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
For backlight curves calculated with the CIE 1931 algorithm set
the brightness scale type to non-linear. This makes the scale type
available to userspace via the 'scale' sysfs attribute.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
- Provide support for ACPI enumeration; gpio_backlight
- Fix-ups
- SPDX fixups; pwm_bl
- Fix linear brightness levels to include number available; pwm_bl
-----BEGIN PGP SIGNATURE-----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=RKbo
-----END PGP SIGNATURE-----
Merge tag 'backlight-next-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight
Pull backlight updates from Lee Jones:
"New Functionality:
- Provide support for ACPI enumeration; gpio_backlight
Fix-ups:
- SPDX fixups; pwm_bl
- Fix linear brightness levels to include number available; pwm_bl"
* tag 'backlight-next-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight:
backlight: pwm_bl: Fix heuristic to determine number of brightness levels
backlight: gpio_backlight: Enable ACPI enumeration
backlight: pwm_bl: Convert to use SPDX identifier
With commit 88ba95bedb ("backlight: pwm_bl: Compute brightness of
LED linearly to human eye") the number of set bits (aka hweight())
in the PWM period is used in the heuristic to determine the number
of brightness levels, when the brightness table isn't specified in
the DT. The number of set bits doesn't provide a reliable clue about
the length of the period, instead change the heuristic to:
nlevels = period / fls(period)
Also limit the maximum number of brightness levels to 4096 to avoid
excessively large tables.
With this the number of levels increases monotonically with the PWM
period, until the maximum of 4096 levels is reached:
period (ns) # levels
100 16
500 62
1000 111
5000 416
10000 769
50000 3333
100000 4096
Fixes: 88ba95bedb ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reduce size of duplicated comments by switching to use SPDX identifier.
No functional change.
While here, correct MODULE_LICENSE() string to be aligned with license text.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The integer exponentiation is used in few places and might be used in
the future by other call sites. Move it to wider use.
Link: http://lkml.kernel.org/r/20190323172531.80025-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
gpiod_get_value() gives out a warning if access to the underlying gpiochip
requires sleeping, which is common for I2C based chips:
WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100
Modules linked in:
CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90
Hardware name: Allwinner sun4i/sun5i Families
Workqueue: events deferred_probe_work_func
[<c010ec50>] (unwind_backtrace) from [<c010b784>] (show_stack+0x10/0x14)
[<c010b784>] (show_stack) from [<c0797224>] (dump_stack+0x88/0x9c)
[<c0797224>] (dump_stack) from [<c0125b08>] (__warn+0xe8/0x100)
[<c0125b08>] (__warn) from [<c0125bd0>] (warn_slowpath_null+0x20/0x28)
[<c0125bd0>] (warn_slowpath_null) from [<c037069c>] (gpiod_get_value+0xd0/0x100)
[<c037069c>] (gpiod_get_value) from [<c03778d0>] (pwm_backlight_probe+0x238/0x508)
[<c03778d0>] (pwm_backlight_probe) from [<c0411a2c>] (platform_drv_probe+0x50/0xac)
[<c0411a2c>] (platform_drv_probe) from [<c0410224>] (driver_probe_device+0x238/0x2e8)
[<c0410224>] (driver_probe_device) from [<c040e820>] (bus_for_each_drv+0x44/0x94)
[<c040e820>] (bus_for_each_drv) from [<c040ff0c>] (__device_attach+0xb0/0x114)
[<c040ff0c>] (__device_attach) from [<c040f4f8>] (bus_probe_device+0x84/0x8c)
[<c040f4f8>] (bus_probe_device) from [<c040f944>] (deferred_probe_work_func+0x50/0x14c)
[<c040f944>] (deferred_probe_work_func) from [<c013be84>] (process_one_work+0x1ec/0x414)
[<c013be84>] (process_one_work) from [<c013ce5c>] (worker_thread+0x2b0/0x5a0)
[<c013ce5c>] (worker_thread) from [<c0141908>] (kthread+0x14c/0x154)
[<c0141908>] (kthread) from [<c0107ab0>] (ret_from_fork+0x14/0x24)
This was missed in commit 0c9501f823 ("backlight: pwm_bl: Handle gpio
that can sleep"). The code was then moved to a separate function in
commit 7613c92231 ("backlight: pwm_bl: Move the checks for initial power
state to a separate function").
The only usage of gpiod_get_value() is during the probe stage, which is
safe to sleep in. Switch to gpiod_get_value_cansleep().
Fixes: 0c9501f823 ("backlight: pwm_bl: Handle gpio that can sleep")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
linearly to human eye")' allows the possibility to compute a default
brightness table when there isn't the brightness-levels property in the
DT. Unfortunately the changes made broke the pwm backlight for the
non-DT boards.
Usually, the non-DT boards don't pass the brightness levels via platform
data, instead, it sets the max_brightness in their platform data and the
driver calculates the level without a table. The offending patch assumed
that when there is no brightness levels table we should create one, but this
is clearly wrong for the non-DT case.
After this patch the code handles the DT and the non-DT case taking in
consideration also if max_brightness is set or not.
Fixes: 88ba95bedb ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")
Reported-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Commit 88ba95bedb ("backlight: pwm_bl: Compute brightness of LED linearly
to human eye") made the parse-dt function return early when using an auto-
generated brightness-table, but didn't take into account that some more
settings were handled below the brightness handling, like power-on-delays
and also setting the pdata enable-gpio to -EINVAL.
This surfaces for example in the case of a backlight without any
enable-gpio which then tries to use gpio-0 in error.
Fix this by simply moving the trailing settings above the brightness
handling.
Fixes: 88ba95bedb ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")
Signed-off-by: Heiko Stuebner <heiko.stuebner@bq.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Commit e6bcca0890 ("backlight: pwm_bl: Switch to using "atomic" PWM API")
removed the driver internal enabled tracking in favor of simply checking
the pwm state.
This can lead to issues as all of gpio-, regulator- and pwm-state are used
to determine the initial state and the bootloader or kernel can leave them
in an inconsistent state at boot.
In my case on rk3399-kevin, the pwm backlight is build as module and the
kernel disables the supply regulator as unused while keeping the pwm running
thus pwm_bl calling pwm_backlight_power_off() during probe and creating an
unmatched regulator-disable call, as it never got enabled from the pwm-bl
before.
To prevent these consistency issues, reintroduce the driver-internal
tracking of the enabled state.
Fixes: e6bcca0890 ("backlight: pwm_bl: Switch to using "atomic" PWM API")
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
The "atomic" API allows us to configure PWM period and duty_cycle and
enable it in one call.
The patch also moves the pwm_init_state just before any use of the
pwm_state struct, this fixes a potential bug where pwm_get_state
can be called before pwm_init_state.
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix with a simple initialize to zero.
Fixes: 573fe6d1c2 ("backlight: pwm_bl: Linear interpolation between brightness-levels")
Reported-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
When you want to change the brightness using a PWM signal, one thing you
need to consider is how human perceive the brightness. Human perceive
the brightness change non-linearly, we have better sensitivity at low
luminance than high luminance, so to achieve perceived linear dimming,
the brightness must be matches to the way our eyes behave. The CIE 1931
lightness formula is what actually describes how we perceive light.
This patch computes a default table with the brightness levels filled
with the numbers provided by the CIE 1931 algorithm, the number of the
brightness levels is calculated based on the PWM resolution.
The calculation of the table using the CIE 1931 algorithm is enabled by
default when you do not define the 'brightness-levels' propriety in your
device tree.
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Setting num-interpolated-steps in the dts will allow you to have linear
interpolation between values of brightness-levels. This way a high
resolution pwm duty cycle can be used without having to list out every
possible value in the dts. This system also allows for gamma corrected
values.
The most simple example is interpolate between two brightness values a
number of steps, this can be done setting the following in the dts:
brightness-levels = <0 65535>;
num-interpolated-steps = <1024>;
default-brightness-level = <512>;
This will create a brightness-level table with the following values:
<0 63 126 189 252 315 378 441 ... 64260 64323 64386 64449 65535>
Another use case can be describe a gamma corrected curve, as we have
better sensitivity at low luminance than high luminance we probably
want have smaller steps for low brightness levels values and bigger
steps for high brightness levels values. This can be achieved with
the following in the dts:
brightness-levels = <0 4096 65535>;
num-interpolated-steps = <1024>;
default-brightness-level = <512>;
This will create a brightness-levels table with the following values:
<0 4 8 12 16 20 ... 4096 4156 4216 4276 ... 65535>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
The documentation was wrong, gpiod_get_direction() returns 0/1 instead
of the GPIOF_* flags. The docs were fixed with commit 94fc73094a
("gpio: correct docs about return value of gpiod_get_direction"). Now,
fix this user (until a better, system-wide solution is in place).
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Some panels (i.e. N116BGE-L41), in their power sequence specifications,
request a delay between set the PWM signal and enable the backlight and
between clear the PWM signal and disable the backlight. Add support for
the new post-pwm-on-delay-ms and pwm-off-delay-ms proprieties to meet
the timings.
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Before this patch the enable signal was set before the PWM signal and
vice-versa on power off. This sequence is wrong, at least, it is on
the different panels datasheets that I checked, so I inverted the sequence
to follow the specs.
For reference the following panels have the mentioned sequence:
- N133HSE-EA1 (Innolux)
- N116BGE (Innolux)
- N156BGE-L21 (Innolux)
- B101EAN0 (Auo)
- B101AW03 (Auo)
- LTN101NT05 (Samsung)
- CLAA101WA01A (Chunghwa)
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This fixes an overflow condition that can happen with high max
brightness and period values in compute_duty_cycle. This fixes it by
using a 64 bit variable for computing the duty cycle.
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
of_device_ids are not supposed to change at runtime. All functions
working with of_device_ids provided by <linux/of.h> work with const
of_device_ids. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Commit 7613c92231 ("backlight: pwm_bl: Move the checks for initial
power state to a separate function") not just moved some code, but made
slight changes in semantics.
If a gpiochip doesn't implement the optional .get_direction() callback,
gpiod_get_direction always returns -EINVAL, which is never equal to
GPIOF_DIR_IN, leading to the GPIO not being configured for output.
To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
like the original code did.
This restores the display on r8a7740/armadillo.
Fixes: 7613c92231 ("backlight: pwm_bl: Move the checks for initial power state to a separate function")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
If the PWM is not enabled the backlight initially should not be enabled
either if we have booted with DT and there is a phandle pointing to the
backlight node.
The patch extends the checks to decide if we should keep the backlight off
initially.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Move the checks to select the initial state for the backlight to a new
function and document the checks we are doing.
With the separate function it is going to be easier to fix or improve the
initial power state configuration later and it is easier to read the code.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Some backlight GPIOs might be connected to some i2c based expanders whose
access might sleep.
Since it's not in any critical path, use the cansleep variant of the GPIO
API.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
The PWM framework has clarified the concept of reference PWM config (the
platform dependent config retrieved from the DT or the PWM lookup table)
and real PWM state.
Use pwm_get_args() when the PWM user wants to retrieve this reference
config and not the current state.
This is part of the rework allowing the PWM framework to support
hardware readout and expose real PWM state even when the PWM has just
been requested (before the user calls pwm_config/enable/disable()).
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
The PWM period will be set when calling pwm_config. Remove this useless
call to pwm_set_period(), which might mess up the internal PWM state.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
If pwm is requested by legacy pwm_request() and if the following
backlight_device_register() call fails, add pwm_free() clean-up.
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Commit ee65ad0e2a9e ("backlight: pwm_bl: Avoid backlight flicker when
probed from DT") tries to dereference the device of_node pointer
unconditionally, causing a NULL pointer dereference on non-dt platforms.
Fix it by replacing the phandle variable with a node variable and
by checking that for NULL before dereferencing it.
Reported-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
If the driver is probed from the device tree, and there is a phandle
property set on it, and the enable GPIO is already configured as output,
and the backlight is currently disabled, keep it disabled.
If all these conditions are met, assume there will be some other driver
that can enable the backlight at the appropriate time.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Platform PWM backlight data provided by board's device tree should be
complete enough to successfully request a pwm device using pwm_get()
API. This change fixes a bug, when an arbitrary (first found) PWM is
connected to a "pwm-backlight" compatible device, when explicit PWM
device reference is not given.
Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
already describes "pwms" as a required property, instead of blind
selection of a potentially wrong PWM reject legacy PWM device
registration request, leave legacy API only for non-dt cases.
Based on initial implementation done by Dmitry Eremin-Solenikov.
Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Since 39b2bbe3d7 (gpio: add flags argument to gpiod_get*() functions),
the gpiod_get* functions take an additional parameter that allows to
specify direction and initial value for output.
Simplify the usage of devm_gpiod_get_optional accordingly.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Uwe Kleine-König