[PATCH v4 000/115] pwm: Fix lifetime issues for pwm_chips
Uwe Kleine-König
u.kleine-koenig at pengutronix.de
Wed Dec 6 03:43:14 PST 2023
Hello,
This series is based on Thierry's for-next.
It starts with some cleanups that were all sent out separately already:
- "pwm: Reduce number of pointer dereferences in pwm_device_request()"
https://lore.kernel.org/linux-pwm/20231130072105.966848-1-u.kleine-koenig@pengutronix.de
- "pwm: crc: Use consistent variable naming for driver data"
https://lore.kernel.org/linux-pwm/20231130074133.969806-1-u.kleine-koenig@pengutronix.de
- Two leds/qcom-lpg patches
https://lore.kernel.org/linux-leds/20231126095230.683204-1-u.kleine-koenig@pengutronix.de
Lee already claimed to have taken the series already, but it's not yet in
next.
- "leds: qcom-lpg: Introduce a wrapper for getting driver data from a pwm chip"
https://lore.kernel.org/linux-leds/20231124215208.616551-3-u.kleine-koenig@pengutronix.de
In the following patches I changed:
- "pwm: cros-ec: Change prototype of helper to prepare further changes" +
This was simplified in response to feedback by Tzung-Bi Shih
- Make pwmchip_priv() static (and don't export it), let drivers use a new
pwmchip_get_drvdata() instead.
- For drm/ti-sn65dsi86.c and leds/qcom-lpg make use of
pwmchip_set_drvdata() which makes the conversion to
devm_pwmchip_alloc() much prettier.
- Some cleanups here and there
- Add review tags received in v3
I kept all tags even though the pwmchip_alloc() patches changed
slightly. Most of the time that's only
s/pwmchip_priv/pwmchip_get_drvdata/ though. Still, if you object,
just tell me. (This affects Paul Cercueil on patch #68, Conor Dooley
on patch #76 and Greg for patch #109.)
I kept the pwmchip_alloc() + pwmchip_register() approach despite Bart
not liking it. To balance that out I don't like Bart's alternative
approach. There are no technically relevant differences between the two
approaches and no benchmarks that show either of the two to be better
than the other. Conceptually the design ideas around pwmchip_alloc() +
pwmchip_register() are used in several other subsystems, so it's a
proven way to do things.
In the discussion about v3 Bart pointed out that there is an imbalance
in the function naming, as pwmchip_alloc() must be paired with
pwmchip_put() (and not something like pwmchip_free()). (This is hidden
from the drivers though, as they all use a devm_pwmchip_alloc() which
does the right thing for them.) I could be talked into renaming
pwmchip_alloc() to pwmchip_get_new(). I hesitated to do that though as
other subsystems also use foo_alloc() and I'm ambivalent about which is
the better name.
Thierry objected to patch "pwm: Ensure that pwm_chips are allocated
using pwmchip_alloc()". I still think it's a nice idea to do that. It
only adds very little overhead in a slow path and might save some time
for people working on an out-of-tree driver. So it also helps the folks
who currently work on new drivers for mainline who rebase on a tree
containing this series. I won't insist about that one though, it can
just be dropped.
Otherwise I should have addressed all feedback and hope the series is
now pretty enough to not cause further concerns.
The last patch shows a prototype of the motivation for improving the
lifetime tracking implemented in this series. It contains a character
device userspace API to use PWMs that is considerably faster and easier
to use than the sysfs API; apply() is faster by a factor of 4 on my test
machine (arm/stm32mp1).
Note that currently there is no known issue with lifetimes in the pwm
subsystem as device links ensure that consumers go away if a pwm_chip
gets unbound. There was an issue before, but that wasn't PWM specific
and is fixed in v6.7-rc1~77^2~3 ("driver core: Release all resources
during unbind before updating device links")[1]
In the presence of character devices making use of PWMs, such an
improved lifetime tracking becomes necessary, otherwise unloading
drivers (or unbinding/hotplugging devices) might crash the kernel.
As calls to .apply() are serialized now, the locking in several drivers
could just be dropped in a future cleanup. I didn't do that now to not
enlarge the series still more and maybe the locking in the core can be
changed to be more fine-grained (abusing(?) a reader-writer-lock) which
would allow concurrent callers for different lines of a single pwm_chip.
In that case the locking must not be dropped.
Also the explicit device links could be dropped now as they are not
strictly needed any more (though requested PWMs might just stop working
when the lowlevel driver is unbound which is a bit ugly, but can happen
at any time for other reasons). Also on systems probed from device tree
there are device links between consumers and providers anyhow. (Don't
know about ACPI systems, I think there are device links then.)
Best regards
Uwe
[1] This fix is also backported to the various stable releases
(v6.6.3, v6.5.13, v6.1.64, v5.15.140; about to go into v5.10.x, v5.4.x,
v4.19.x and v4.14.x)
Uwe Kleine-König (115):
pwm: Reduce number of pointer dereferences in pwm_device_request()
pwm: crc: Use consistent variable naming for driver data
leds: qcom-lpg: Use devm_pwmchip_add() simplifying driver removal
leds: qcom-lpg: Consistenly use dev_err_probe() in .probe()'s error path
leds: qcom-lpg: Introduce a wrapper for getting driver data from a pwm chip
pwm: cros-ec: Change prototype of helpers to prepare further changes
pwm: Provide a macro to get the parent device of a given chip
pwm: ab8500: Make use of pwmchip_parent() macro
pwm: atmel: Make use of pwmchip_parent() macro
pwm: atmel-tcb: Make use of pwmchip_parent() macro
pwm: bcm-kona: Make use of pwmchip_parent() macro
pwm: crc: Make use of pwmchip_parent() macro
pwm: cros-ec: Make use of pwmchip_parent() macro
pwm: dwc: Make use of pwmchip_parent() macro
pwm: ep93xx: Make use of pwmchip_parent() macro
pwm: fsl-ftm: Make use of pwmchip_parent() macro
pwm: img: Make use of parent device pointer in driver data
pwm: imx27: Make use of pwmchip_parent() macro
pwm: jz4740: Make use of pwmchip_parent() macro
pwm: lpc18xx-sct: Make use of parent device pointer in driver data
pwm: lpss: Make use of pwmchip_parent() macro
pwm: mediatek: Make use of pwmchip_parent() macro
pwm: meson: Make use of pwmchip_parent() macro
pwm: mtk-disp: Make use of pwmchip_parent() macro
pwm: omap: Make use of pwmchip_parent() macro
pwm: pca9685: Store parent device in driver data
pwm: raspberrypi-poe: Make use of pwmchip_parent() macro
pwm: rcar: Make use of pwmchip_parent() macro
pwm: rz-mtu3: Make use of pwmchip_parent() macro
pwm: samsung: Make use of pwmchip_parent() macro
pwm: sifive: Make use of pwmchip_parent() macro
pwm: stm32-lp: Make use of pwmchip_parent() macro
pwm: stm32: Make use of pwmchip_parent() macro
pwm: stmpe: Make use of pwmchip_parent() macro
pwm: sun4i: Make use of pwmchip_parent() macro
pwm: tiecap: Make use of pwmchip_parent() macro
pwm: tiehrpwm: Make use of pwmchip_parent() macro
pwm: twl-led: Make use of pwmchip_parent() macro
pwm: twl: Make use of pwmchip_parent() macro
pwm: vt8500: Make use of pwmchip_parent() macro
staging: greybus: pwm: Make use of pwmchip_parent() macro
pwm: Provide wrappers for storing and getting driver private data
pwm: Provide devm_pwmchip_alloc() function
pwm: ab8500: Make use of devm_pwmchip_alloc() function
pwm: apple: Make use of devm_pwmchip_alloc() function
pwm: atmel-hlcdc: Make use of devm_pwmchip_alloc() function
pwm: atmel: Make use of devm_pwmchip_alloc() function
pwm: atmel-tcb: Make use of devm_pwmchip_alloc() function
pwm: bcm2835: Make use of devm_pwmchip_alloc() function
pwm: bcm-iproc: Make use of devm_pwmchip_alloc() function
pwm: bcm-kona: Make use of devm_pwmchip_alloc() function
pwm: berlin: Make use of devm_pwmchip_alloc() function
pwm: brcmstb: Make use of devm_pwmchip_alloc() function
pwm: clk: Make use of devm_pwmchip_alloc() function
pwm: clps711x: Make use of devm_pwmchip_alloc() function
pwm: crc: Make use of devm_pwmchip_alloc() function
pwm: cros-ec: Make use of devm_pwmchip_alloc() function
pwm: dwc: Make use of devm_pwmchip_alloc() function
pwm: ep93xx: Make use of devm_pwmchip_alloc() function
pwm: fsl-ftm: Make use of devm_pwmchip_alloc() function
pwm: hibvt: Make use of devm_pwmchip_alloc() function
pwm: img: Make use of devm_pwmchip_alloc() function
pwm: imx1: Make use of devm_pwmchip_alloc() function
pwm: imx27: Make use of devm_pwmchip_alloc() function
pwm: imx-tpm: Make use of devm_pwmchip_alloc() function
pwm: intel-lgm: Make use of devm_pwmchip_alloc() function
pwm: iqs620a: Make use of devm_pwmchip_alloc() function
pwm: jz4740: Make use of devm_pwmchip_alloc() function
pwm: keembay: Make use of devm_pwmchip_alloc() function
pwm: lp3943: Make use of devm_pwmchip_alloc() function
pwm: lpc18xx-sct: Make use of devm_pwmchip_alloc() function
pwm: lpc32xx: Make use of devm_pwmchip_alloc() function
pwm: lpss-*: Make use of devm_pwmchip_alloc() function
pwm: mediatek: Make use of devm_pwmchip_alloc() function
pwm: meson: Make use of devm_pwmchip_alloc() function
pwm: microchip-core: Make use of devm_pwmchip_alloc() function
pwm: mtk-disp: Make use of devm_pwmchip_alloc() function
pwm: mxs: Make use of devm_pwmchip_alloc() function
pwm: ntxec: Make use of devm_pwmchip_alloc() function
pwm: omap-dmtimer: Make use of devm_pwmchip_alloc() function
pwm: pca9685: Make use of devm_pwmchip_alloc() function
pwm: pxa: Make use of devm_pwmchip_alloc() function
pwm: raspberrypi-poe: Make use of devm_pwmchip_alloc() function
pwm: rcar: Make use of devm_pwmchip_alloc() function
pwm: renesas-tpu: Make use of devm_pwmchip_alloc() function
pwm: rockchip: Make use of devm_pwmchip_alloc() function
pwm: rz-mtu3: Make use of devm_pwmchip_alloc() function
pwm: samsung: Make use of devm_pwmchip_alloc() function
pwm: sifive: Make use of devm_pwmchip_alloc() function
pwm: sl28cpld: Make use of devm_pwmchip_alloc() function
pwm: spear: Make use of devm_pwmchip_alloc() function
pwm: sprd: Make use of devm_pwmchip_alloc() function
pwm: sti: Make use of devm_pwmchip_alloc() function
pwm: stm32-lp: Make use of devm_pwmchip_alloc() function
pwm: stm32: Make use of devm_pwmchip_alloc() function
pwm: stmpe: Make use of devm_pwmchip_alloc() function
pwm: sun4i: Make use of devm_pwmchip_alloc() function
pwm: sunplus: Make use of devm_pwmchip_alloc() function
pwm: tegra: Make use of devm_pwmchip_alloc() function
pwm: tiecap: Make use of devm_pwmchip_alloc() function
pwm: twl-led: Make use of devm_pwmchip_alloc() function
pwm: twl: Make use of devm_pwmchip_alloc() function
pwm: visconti: Make use of devm_pwmchip_alloc() function
pwm: vt8500: Make use of devm_pwmchip_alloc() function
pwm: xilinx: Make use of devm_pwmchip_alloc() function
gpio: mvebu: Make use of devm_pwmchip_alloc() function
drm/bridge: ti-sn65dsi86: Make use of devm_pwmchip_alloc() function
leds: qcom-lpg: Make use of devm_pwmchip_alloc() function
staging: greybus: pwm: Make use of devm_pwmchip_alloc() function
pwm: Ensure that pwm_chips are allocated using pwmchip_alloc()
pwm: Ensure a struct pwm has the same lifetime as its pwm_chip
pwm: Ensure the memory backing a PWM chip isn't freed while used
pwm: Add more locking
pwm: Make pwmchip_[sg]et_drvdata a wrapper around dev_set_drvdata
WIP: pwm: Add support for pwmchip devices for faster and easier userspace access
.../driver-api/driver-model/devres.rst | 1 +
Documentation/driver-api/pwm.rst | 10 +-
drivers/gpio/gpio-mvebu.c | 18 +-
drivers/gpu/drm/bridge/ti-sn65dsi86.c | 27 +-
drivers/leds/rgb/leds-qcom-lpg.c | 75 ++-
drivers/pwm/Kconfig | 4 -
drivers/pwm/Makefile | 3 +-
drivers/pwm/core.c | 490 +++++++++++++++---
drivers/pwm/pwm-ab8500.c | 36 +-
drivers/pwm/pwm-apple.c | 18 +-
drivers/pwm/pwm-atmel-hlcdc.c | 35 +-
drivers/pwm/pwm-atmel-tcb.c | 26 +-
drivers/pwm/pwm-atmel.c | 37 +-
drivers/pwm/pwm-bcm-iproc.c | 19 +-
drivers/pwm/pwm-bcm-kona.c | 21 +-
drivers/pwm/pwm-bcm2835.c | 17 +-
drivers/pwm/pwm-berlin.c | 29 +-
drivers/pwm/pwm-brcmstb.c | 17 +-
drivers/pwm/pwm-clk.c | 27 +-
drivers/pwm/pwm-clps711x.c | 21 +-
drivers/pwm/pwm-crc.c | 26 +-
drivers/pwm/pwm-cros-ec.c | 55 +-
drivers/pwm/pwm-dwc-core.c | 25 +-
drivers/pwm/pwm-dwc.c | 18 +-
drivers/pwm/pwm-dwc.h | 9 +-
drivers/pwm/pwm-ep93xx.c | 21 +-
drivers/pwm/pwm-fsl-ftm.c | 48 +-
drivers/pwm/pwm-hibvt.c | 25 +-
drivers/pwm/pwm-img.c | 51 +-
drivers/pwm/pwm-imx-tpm.c | 34 +-
drivers/pwm/pwm-imx1.c | 20 +-
drivers/pwm/pwm-imx27.c | 26 +-
drivers/pwm/pwm-intel-lgm.c | 17 +-
drivers/pwm/pwm-iqs620a.c | 37 +-
drivers/pwm/pwm-jz4740.c | 35 +-
drivers/pwm/pwm-keembay.c | 17 +-
drivers/pwm/pwm-lp3943.c | 17 +-
drivers/pwm/pwm-lpc18xx-sct.c | 35 +-
drivers/pwm/pwm-lpc32xx.c | 21 +-
drivers/pwm/pwm-lpss-pci.c | 10 +-
drivers/pwm/pwm-lpss-platform.c | 10 +-
drivers/pwm/pwm-lpss.c | 34 +-
drivers/pwm/pwm-lpss.h | 1 -
drivers/pwm/pwm-mediatek.c | 28 +-
drivers/pwm/pwm-meson.c | 57 +-
drivers/pwm/pwm-microchip-core.c | 17 +-
drivers/pwm/pwm-mtk-disp.c | 25 +-
drivers/pwm/pwm-mxs.c | 32 +-
drivers/pwm/pwm-ntxec.c | 30 +-
drivers/pwm/pwm-omap-dmtimer.c | 46 +-
drivers/pwm/pwm-pca9685.c | 98 ++--
drivers/pwm/pwm-pxa.c | 21 +-
drivers/pwm/pwm-raspberrypi-poe.c | 20 +-
drivers/pwm/pwm-rcar.c | 25 +-
drivers/pwm/pwm-renesas-tpu.c | 18 +-
drivers/pwm/pwm-rockchip.c | 24 +-
drivers/pwm/pwm-rz-mtu3.c | 38 +-
drivers/pwm/pwm-samsung.c | 56 +-
drivers/pwm/pwm-sifive.c | 30 +-
drivers/pwm/pwm-sl28cpld.c | 13 +-
drivers/pwm/pwm-spear.c | 17 +-
drivers/pwm/pwm-sprd.c | 50 +-
drivers/pwm/pwm-sti.c | 34 +-
drivers/pwm/pwm-stm32-lp.c | 29 +-
drivers/pwm/pwm-stm32.c | 53 +-
drivers/pwm/pwm-stmpe.c | 58 ++-
drivers/pwm/pwm-sun4i.c | 38 +-
drivers/pwm/pwm-sunplus.c | 17 +-
drivers/pwm/pwm-tegra.c | 27 +-
drivers/pwm/pwm-tiecap.c | 55 +-
drivers/pwm/pwm-tiehrpwm.c | 72 +--
drivers/pwm/pwm-twl-led.c | 58 ++-
drivers/pwm/pwm-twl.c | 50 +-
drivers/pwm/pwm-visconti.c | 17 +-
drivers/pwm/pwm-vt8500.c | 41 +-
drivers/pwm/pwm-xilinx.c | 34 +-
drivers/pwm/sysfs.c | 64 +--
drivers/staging/greybus/pwm.c | 130 ++---
include/linux/platform_data/x86/pwm-lpss.h | 4 +-
include/linux/pwm.h | 43 +-
include/uapi/linux/pwm.h | 23 +
81 files changed, 1690 insertions(+), 1325 deletions(-)
create mode 100644 include/uapi/linux/pwm.h
base-commit: 6d0589a70587116c7ff09e027659c6254f883b2d
--
2.42.0
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