[PATCH] pwm: pwm-tiehrpwm: Use clk_enable/disable instead clk_prepare/unprepare.

From: Marek Belisko
Date: Tue Jun 18 2013 - 07:52:15 EST

This was found when using pwm-led on am33xx and enable
heartbeat trigger.

[ 808.624876] =================================
[ 808.629443] [ INFO: inconsistent lock state ]
[ 808.634021] 3.9.0 #2 Not tainted
[ 808.637415] ---------------------------------
[ 808.641981] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 808.648288] swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[ 808.653494] (prepare_lock){+.?.+.}, at: [<c027c211>] clk_unprepare+0x15/0x24
[ 808.661040] {SOFTIRQ-ON-W} state was registered at:
[ 808.666155] [<c004ec4d>] __lock_acquire+0x411/0x824
[ 808.671465] [<c004f359>] lock_acquire+0x41/0x50
[ 808.676412] [<c039ee9d>] mutex_lock_nested+0x31/0x1d8
[ 808.681912] [<c027c275>] clk_prepare+0x15/0x28
[ 808.686764] [<c0590c6b>] _init+0x117/0x1e0
[ 808.691256] [<c0019ef9>] omap_hwmod_for_each+0x29/0x3c
[ 808.696842] [<c0591107>] __omap_hwmod_setup_all+0x17/0x2c
[ 808.702696] [<c0008653>] do_one_initcall+0xc3/0x10c
[ 808.708017] [<c058a627>] kernel_init_freeable+0xa7/0x134
[ 808.713778] [<c039a543>] kernel_init+0x7/0x98
[ 808.718544] [<c000cd95>] ret_from_fork+0x11/0x3c
[ 808.723583] irq event stamp: 1379172
[ 808.727328] hardirqs last enabled at (1379172): [<c03a0759>] _raw_spin_unlock_irqrestore+0x21/0x30
[ 808.736828] hardirqs last disabled at (1379171): [<c03a03c3>] _raw_spin_lock_irqsave+0x13/0x38
[ 808.745876] softirqs last enabled at (1379164): [<c002ae5d>] irq_enter+0x49/0x4c
[ 808.753747] softirqs last disabled at (1379165): [<c002aec3>] irq_exit+0x63/0x88
[ 808.761518]
[ 808.761518] other info that might help us debug this:
[ 808.768373] Possible unsafe locking scenario:
[ 808.768373]
[ 808.774578] CPU0
[ 808.777141] ----
[ 808.779705] lock(prepare_lock);
[ 808.783186] <Interrupt>
[ 808.785929] lock(prepare_lock);
[ 808.789595]
[ 808.789595] *** DEADLOCK ***
[ 808.789595]
[ 808.795805] 1 lock held by swapper/0:
[ 808.799643] #0: (((&heartbeat_data->timer))){+.-...}, at: [<c002e204>] call_timer_fn+0x0/0x90
[ 808.808814]
[ 808.808814] stack backtrace:
[ 808.813402] [<c000ff19>] (unwind_backtrace+0x1/0x98) from [<c039bd75>] (print_usage_bug.part.25+0x16d/0x1cc)
[ 808.823721] [<c039bd75>] (print_usage_bug.part.25+0x16d/0x1cc) from [<c004e595>] (mark_lock+0x18d/0x434)
[ 808.833669] [<c004e595>] (mark_lock+0x18d/0x434) from [<c004ec1d>] (__lock_acquire+0x3e1/0x824)
[ 808.842803] [<c004ec1d>] (__lock_acquire+0x3e1/0x824) from [<c004f359>] (lock_acquire+0x41/0x50)
[ 808.852031] [<c004f359>] (lock_acquire+0x41/0x50) from [<c039ee9d>] (mutex_lock_nested+0x31/0x1d8)
[ 808.861433] [<c039ee9d>] (mutex_lock_nested+0x31/0x1d8) from [<c027c211>] (clk_unprepare+0x15/0x24)
[ 808.870930] [<c027c211>] (clk_unprepare+0x15/0x24) from [<c019f7bf>] (ehrpwm_pwm_disable+0x5f/0x80)
[ 808.880431] [<c019f7bf>] (ehrpwm_pwm_disable+0x5f/0x80) from [<c019f29f>] (pwm_disable+0x27/0x28)
[ 808.889751] [<c019f29f>] (pwm_disable+0x27/0x28) from [<c026f8f3>] (led_heartbeat_function+0x3f/0xb0)
[ 808.899431] [<c026f8f3>] (led_heartbeat_function+0x3f/0xb0) from [<c002e249>] (call_timer_fn+0x45/0x90)
[ 808.909288] [<c002e249>] (call_timer_fn+0x45/0x90) from [<c002e399>] (run_timer_softirq+0x105/0x17c)
[ 808.918884] [<c002e399>] (run_timer_softirq+0x105/0x17c) from [<c002abc5>] (__do_softirq+0xa5/0x150)
[ 808.928486] [<c002abc5>] (__do_softirq+0xa5/0x150) from [<c002aec3>] (irq_exit+0x63/0x88)
[ 808.937098] [<c002aec3>] (irq_exit+0x63/0x88) from [<c000d599>] (handle_IRQ+0x21/0x54)
[ 808.945415] [<c000d599>] (handle_IRQ+0x21/0x54) from [<c0008495>] (omap3_intc_handle_irq+0x5d/0x68)
[ 808.954900] [<c0008495>] (omap3_intc_handle_irq+0x5d/0x68) from [<c000c7ff>] (__irq_svc+0x3f/0x64)
[ 808.964287] Exception stack(0xc05b1f68 to 0xc05b1fb0)
[ 808.969587] 1f60: 00000001 00000001 00000000 00000000 c05b0000 c0619748
[ 808.978158] 1f80: c05b0000 c05b0000 c0619748 413fc082 00000000 00000000 01000000 c05b1fb0
[ 808.986719] 1fa0: c004f989 c000d6f0 400f0033 ffffffff
[ 808.992024] [<c000c7ff>] (__irq_svc+0x3f/0x64) from [<c000d6f0>] (cpu_idle+0x60/0x98)
[ 809.000250] [<c000d6f0>] (cpu_idle+0x60/0x98) from [<c058a535>] (start_kernel+0x1e9/0x234)

Remove non atomic clk api calls and use only atomic for enable/disable because
can be called from atomic context (led_heartbeat_function is timer callback).

Signed-off-by: Marek Belisko <marek.belisko@xxxxxxxxxxxxxxxxxxx>
---
drivers/pwm/pwm-tiehrpwm.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-tiehrpwm.c b/drivers/pwm/pwm-tiehrpwm.c
index 8b4c86f..97bb788 100644
--- a/drivers/pwm/pwm-tiehrpwm.c
+++ b/drivers/pwm/pwm-tiehrpwm.c
@@ -359,7 +359,7 @@ static int ehrpwm_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
configure_polarity(pc, pwm->hwpwm);

/* Enable TBCLK before enabling PWM device */
- ret = clk_prepare_enable(pc->tbclk);
+ ret = clk_enable(pc->tbclk);
if (ret) {
pr_err("Failed to enable TBCLK for %s\n",
dev_name(pc->chip.dev));
@@ -395,7 +395,7 @@ static void ehrpwm_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
ehrpwm_modify(pc->mmio_base, AQCSFRC, aqcsfrc_mask, aqcsfrc_val);

/* Disabling TBCLK on PWM disable */
- clk_disable_unprepare(pc->tbclk);
+ clk_disable(pc->tbclk);

/* Stop Time base counter */
ehrpwm_modify(pc->mmio_base, TBCTL, TBCTL_RUN_MASK, TBCTL_STOP_NEXT);
@@ -487,6 +487,12 @@ static int ehrpwm_pwm_probe(struct platform_device *pdev)
return PTR_ERR(pc->tbclk);
}

+ ret = clk_prepare(pc->tbclk);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "clk_prepare() failed: %d\n", ret);
+ return ret;
+ }
+
ret = pwmchip_add(&pc->chip);
if (ret < 0) {
dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
--
1.7.9.5

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