From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-pwm@vger.kernel.org, kernel@pengutronix.de
Subject: [PATCH v3 107/108] pwm: Add more locking
Date: Tue, 21 Nov 2023 14:50:49 +0100 [thread overview]
Message-ID: <20231121134901.208535-108-u.kleine-koenig@pengutronix.de> (raw)
In-Reply-To: <20231121134901.208535-1-u.kleine-koenig@pengutronix.de>
This ensures that a pwm_chip that has no corresponding driver isn't used
and that a driver doesn't go away while a callback is still running.
As with the previous commit this is not needed yet, but once we have PWM
character device support this is required for race-free operation.
To not serialize all pwm_apply_state() calls, this introduces a per chip
lock. To prepare for a more sophisticated locking scheme involving spin
locks instead of mutexes for "fast" chips, there are (for now trivial)
functions introduced for locking and unlocking.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
drivers/pwm/core.c | 76 ++++++++++++++++++++++++++++++++++++++-------
include/linux/pwm.h | 6 +++-
2 files changed, 69 insertions(+), 13 deletions(-)
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index dd376fe9e265..8dbc79f7218c 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -32,6 +32,16 @@ static DEFINE_MUTEX(pwm_lock);
static DEFINE_IDR(pwmchip_idr);
+static void pwmchip_lock(struct pwm_chip *chip)
+{
+ mutex_lock(&chip->lock);
+}
+
+static void pwmchip_unlock(struct pwm_chip *chip)
+{
+ mutex_unlock(&chip->lock);
+}
+
static struct pwm_chip *pwmchip_find_by_name(const char *name)
{
struct pwm_chip *chip;
@@ -231,6 +241,7 @@ static struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm,
chip->npwm = npwm;
chip->uses_pwmchip_alloc = true;
+ chip->operational = false;
for (i = 0; i < chip->npwm; i++) {
struct pwm_device *pwm = &chip->pwms[i];
@@ -311,23 +322,29 @@ int __pwmchip_add(struct pwm_chip *chip, struct module *owner)
if (IS_ENABLED(CONFIG_OF))
of_pwmchip_add(chip);
+ mutex_init(&chip->lock);
+
ret = device_add(&chip->dev);
if (ret)
goto err_device_add;
+ pwmchip_lock(chip);
+ chip->operational = true;
+ pwmchip_unlock(chip);
+
mutex_unlock(&pwm_lock);
return 0;
err_device_add:
- if (IS_ENABLED(CONFIG_OF))
- of_pwmchip_remove(chip);
+ of_pwmchip_remove(chip);
idr_remove(&pwmchip_idr, chip->id);
err_idr_alloc:
mutex_unlock(&pwm_lock);
+
module_put(owner);
return ret;
@@ -343,12 +360,27 @@ EXPORT_SYMBOL_GPL(__pwmchip_add);
void pwmchip_remove(struct pwm_chip *chip)
{
pwmchip_sysfs_unexport(chip);
+ unsigned int i;
if (IS_ENABLED(CONFIG_OF))
of_pwmchip_remove(chip);
mutex_lock(&pwm_lock);
+ pwmchip_lock(chip);
+ chip->operational = false;
+ pwmchip_unlock(chip);
+
+ for (i = 0; i < chip->npwm; ++i) {
+ struct pwm_device *pwm = &chip->pwms[i];
+
+ if (test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) {
+ dev_alert(&chip->dev, "Freeing requested PWM #%u\n", i);
+ if (pwm->chip->ops->free)
+ pwm->chip->ops->free(pwm->chip, pwm);
+ }
+ }
+
idr_remove(&pwmchip_idr, chip->id);
mutex_unlock(&pwm_lock);
@@ -524,7 +556,7 @@ static void pwm_apply_state_debug(struct pwm_device *pwm,
int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
{
struct pwm_chip *chip;
- int err;
+ int err = 0;
/*
* Some lowlevel driver's implementations of .apply() make use of
@@ -541,17 +573,24 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
chip = pwm->chip;
+ pwmchip_lock(chip);
+
+ if (!chip->operational) {
+ err = -ENXIO;
+ goto out_unlock;
+ }
+
if (state->period == pwm->state.period &&
state->duty_cycle == pwm->state.duty_cycle &&
state->polarity == pwm->state.polarity &&
state->enabled == pwm->state.enabled &&
state->usage_power == pwm->state.usage_power)
- return 0;
+ goto out_unlock;
err = chip->ops->apply(chip, pwm, state);
trace_pwm_apply(pwm, state, err);
if (err)
- return err;
+ goto out_unlock;
pwm->state = *state;
@@ -561,7 +600,10 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
*/
pwm_apply_state_debug(pwm, state);
- return 0;
+out_unlock:
+ pwmchip_unlock(chip);
+
+ return err;
}
EXPORT_SYMBOL_GPL(pwm_apply_state);
@@ -585,7 +627,12 @@ int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result,
return -ENOSYS;
mutex_lock(&pwm_lock);
- err = pwm->chip->ops->capture(pwm->chip, pwm, result, timeout);
+
+ if (pwm->chip->operational)
+ err = pwm->chip->ops->capture(pwm->chip, pwm, result, timeout);
+ else
+ err = -ENXIO;
+
mutex_unlock(&pwm_lock);
return err;
@@ -992,23 +1039,28 @@ EXPORT_SYMBOL_GPL(pwm_get);
*/
void pwm_put(struct pwm_device *pwm)
{
+ bool operational;
+
if (!pwm)
return;
mutex_lock(&pwm_lock);
- if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) {
- pr_warn("PWM device already freed\n");
+ if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags))
goto out;
- }
- if (pwm->chip->ops->free)
+ pwmchip_lock(pwm->chip);
+ operational = pwm->chip->operational;
+ pwmchip_unlock(pwm->chip);
+
+ if (operational && pwm->chip->ops->free)
pwm->chip->ops->free(pwm->chip, pwm);
pwm->label = NULL;
- put_device(&pwm->chip->dev);
out:
+ put_device(&pwm->chip->dev);
+
mutex_unlock(&pwm_lock);
}
EXPORT_SYMBOL_GPL(pwm_put);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 081c8402155d..4e81e8819f8c 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -287,7 +287,9 @@ struct pwm_ops {
* @npwm: number of PWMs controlled by this chip
* @of_xlate: request a PWM device given a device tree PWM specifier
* @of_pwm_n_cells: number of cells expected in the device tree PWM specifier
- * @list: list node for internal use
+ * @lock: mutex protecting .operational and serializing ops and chip unregistration
+ * @uses_pwmchip_alloc: signals if pwmchip_allow was used to allocate this chip
+ * @operational: tracks if the chip is operational
* @pwms: array of PWM devices allocated by the framework
*/
struct pwm_chip {
@@ -302,7 +304,9 @@ struct pwm_chip {
unsigned int of_pwm_n_cells;
/* only used internally by the PWM framework */
+ struct mutex lock;
bool uses_pwmchip_alloc;
+ bool operational;
struct pwm_device pwms[] __counted_by(npwm);
};
--
2.42.0
next prev parent reply other threads:[~2023-11-21 13:52 UTC|newest]
Thread overview: 163+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 13:49 [PATCH v3 000/108] pwm: Fix lifetime issues for pwm_chips Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 001/108] pwm: cros-ec: Change prototype of helper to prepare further changes Uwe Kleine-König
2023-11-22 8:52 ` Tzung-Bi Shih
2023-11-23 9:24 ` Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 002/108] pwm: Provide a macro to get the parent device of a given chip Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 003/108] pwm: ab8500: Make use of pwmchip_parent() macro Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 004/108] pwm: atmel: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 005/108] pwm: atmel-tcb: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 006/108] pwm: bcm-kona: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 007/108] pwm: crc: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 008/108] pwm: cros-ec: " Uwe Kleine-König
2023-11-22 8:52 ` Tzung-Bi Shih
2023-11-21 13:49 ` [PATCH v3 009/108] pwm: dwc: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 010/108] pwm: ep93xx: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 011/108] pwm: fsl-ftm: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 012/108] pwm: img: Make use of parent device pointer in driver data Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 013/108] pwm: imx27: Make use of pwmchip_parent() macro Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 014/108] pwm: jz4740: " Uwe Kleine-König
2023-11-21 14:13 ` Paul Cercueil
2023-11-21 15:51 ` Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 015/108] pwm: lpc18xx-sct: Make use of parent device pointer in driver data Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 016/108] pwm: lpss: Make use of pwmchip_parent() macro Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 017/108] pwm: mediatek: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 018/108] pwm: meson: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 019/108] pwm: mtk-disp: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 020/108] pwm: omap: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 021/108] pwm: pca9685: Store parent device in driver data Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 022/108] pwm: raspberrypi-poe: Make use of pwmchip_parent() macro Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 023/108] pwm: rcar: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 024/108] pwm: rz-mtu3: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 025/108] pwm: samsung: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 026/108] pwm: sifive: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 027/108] pwm: stm32-lp: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 028/108] pwm: stm32: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 029/108] pwm: stmpe: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 030/108] pwm: sun4i: " Uwe Kleine-König
2023-11-25 18:48 ` Jernej Škrabec
2023-11-21 13:49 ` [PATCH v3 031/108] pwm: tiecap: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 032/108] pwm: tiehrpwm: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 033/108] pwm: twl-led: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 034/108] pwm: twl: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 035/108] pwm: vt8500: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 036/108] staging: greybus: pwm: " Uwe Kleine-König
2023-11-23 12:55 ` Greg Kroah-Hartman
2023-11-21 13:49 ` [PATCH v3 037/108] pwm: Provide devm_pwmchip_alloc() function Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 038/108] pwm: ab8500: Make use of " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 039/108] pwm: apple: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 040/108] pwm: atmel-hlcdc: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 041/108] pwm: atmel: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 042/108] pwm: atmel-tcb: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 043/108] pwm: bcm2835: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 044/108] pwm: bcm-iproc: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 045/108] pwm: bcm-kona: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 046/108] pwm: berlin: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 047/108] pwm: brcmstb: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 048/108] pwm: clk: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 049/108] pwm: clps711x: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 050/108] pwm: crc: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 051/108] pwm: cros-ec: " Uwe Kleine-König
2023-11-22 8:52 ` Tzung-Bi Shih
2023-11-22 23:56 ` Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 052/108] pwm: dwc: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 053/108] pwm: ep93xx: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 054/108] pwm: fsl-ftm: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 055/108] pwm: hibvt: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 056/108] pwm: img: " Uwe Kleine-König
2023-11-21 13:49 ` [PATCH v3 057/108] pwm: imx1: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 058/108] pwm: imx27: " Uwe Kleine-König
2023-12-05 11:49 ` Philipp Zabel
2023-12-05 12:14 ` Uwe Kleine-König
2023-12-05 12:50 ` Philipp Zabel
2023-11-21 13:50 ` [PATCH v3 059/108] pwm: imx-tpm: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 060/108] pwm: intel-lgm: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 061/108] pwm: iqs620a: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 062/108] pwm: jz4740: " Uwe Kleine-König
2023-11-21 14:16 ` Paul Cercueil
2023-11-21 13:50 ` [PATCH v3 063/108] pwm: keembay: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 064/108] pwm: lp3943: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 065/108] pwm: lpc18xx-sct: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 066/108] pwm: lpc32xx: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 067/108] pwm: lpss-*: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 068/108] pwm: mediatek: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 069/108] pwm: meson: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 070/108] pwm: microchip-core: " Uwe Kleine-König
2023-11-22 11:14 ` Conor Dooley
2023-11-22 22:48 ` Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 071/108] pwm: mtk-disp: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 072/108] pwm: mxs: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 073/108] pwm: ntxec: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 074/108] pwm: omap-dmtimer: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 075/108] pwm: pca9685: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 076/108] pwm: pxa: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 077/108] pwm: raspberrypi-poe: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 078/108] pwm: rcar: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 079/108] pwm: renesas-tpu: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 080/108] pwm: rockchip: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 081/108] pwm: rz-mtu3: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 082/108] pwm: samsung: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 083/108] pwm: sifive: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 084/108] pwm: sl28cpld: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 085/108] pwm: spear: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 086/108] pwm: sprd: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 087/108] pwm: sti: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 088/108] pwm: stm32-lp: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 089/108] pwm: stm32: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 090/108] pwm: stmpe: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 091/108] pwm: sun4i: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 092/108] pwm: sunplus: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 093/108] pwm: tegra: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 094/108] pwm: tiecap: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 095/108] pwm: twl-led: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 096/108] pwm: twl: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 097/108] pwm: visconti: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 098/108] pwm: vt8500: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 099/108] pwm: xilinx: " Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 100/108] gpio: mvebu: " Uwe Kleine-König
2023-11-21 14:02 ` Bartosz Golaszewski
2023-11-21 16:11 ` Uwe Kleine-König
2023-11-22 9:05 ` Uwe Kleine-König
2023-11-22 10:36 ` Bartosz Golaszewski
2023-11-22 23:39 ` Uwe Kleine-König
2023-11-24 12:14 ` Thierry Reding
2023-11-24 21:16 ` Bartosz Golaszewski
2023-11-24 21:59 ` Uwe Kleine-König
2023-11-27 10:58 ` Uwe Kleine-König
2023-11-27 20:22 ` Bartosz Golaszewski
2023-11-28 9:07 ` Uwe Kleine-König
2023-12-01 10:14 ` Bartosz Golaszewski
2023-12-02 0:43 ` Uwe Kleine-König
2023-12-04 20:27 ` Bartosz Golaszewski
2023-12-04 21:28 ` Bartosz Golaszewski
2023-12-05 9:31 ` Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 101/108] drm/bridge: ti-sn65dsi86: " Uwe Kleine-König
2023-11-21 15:15 ` Doug Anderson
2023-11-21 16:05 ` Uwe Kleine-König
2023-11-21 16:14 ` Doug Anderson
2023-11-23 9:17 ` Uwe Kleine-König
2023-11-27 9:32 ` Uwe Kleine-König
2023-11-23 9:46 ` Laurent Pinchart
2023-11-23 10:10 ` Uwe Kleine-König
2023-12-06 12:06 ` Laurent Pinchart
2023-12-06 14:23 ` Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 102/108] leds: qcom-lpg: " Uwe Kleine-König
2023-11-21 15:16 ` Lee Jones
2023-11-21 15:58 ` Uwe Kleine-König
2023-11-22 11:56 ` Lee Jones
2023-11-22 17:15 ` Thierry Reding
2023-11-23 10:44 ` Uwe Kleine-König
2023-11-24 12:27 ` Thierry Reding
2023-11-24 18:22 ` Uwe Kleine-König
2023-11-24 21:21 ` Bartosz Golaszewski
2023-11-22 17:54 ` Uwe Kleine-König
2023-11-23 10:21 ` Lee Jones
2023-11-23 10:54 ` Uwe Kleine-König
2023-11-21 13:50 ` [PATCH v3 104/108] pwm: Ensure that pwm_chips are allocated using pwmchip_alloc() Uwe Kleine-König
2023-11-22 17:19 ` Thierry Reding
2023-11-22 23:52 ` Uwe Kleine-König
2023-11-24 12:28 ` Thierry Reding
2023-11-21 13:50 ` [PATCH v3 105/108] pwm: Ensure a struct pwm has the same lifetime as its pwm_chip Uwe Kleine-König
2023-11-21 15:53 ` Gustavo A. R. Silva
2023-11-21 13:50 ` [PATCH v3 106/108] pwm: Ensure the memory backing a PWM chip isn't freed while used Uwe Kleine-König
2023-11-21 13:50 ` Uwe Kleine-König [this message]
2023-11-21 13:50 ` [PATCH v3 108/108] WIP: pwm: Add support for pwmchip devices for faster and easier userspace access Uwe Kleine-König
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