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pwm: fsl-ftm: Use flat regmap cache

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Use flat regmap cache to avoid lockdep warning at probe:

[    0.697285] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0x15c/0x160()
[    0.697449] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))

The RB-tree regmap cache needs to allocate new space on first writes.
However, allocations in an atomic context (e.g. when a spinlock is held)
are not allowed. The function regmap_write calls map->lock, which
acquires a spinlock in the fast_io case. Since the pwm-fsl-ftm driver
uses MMIO, the regmap bus of type regmap_mmio is being used which has
fast_io set to true.

The MMIO space of the pwm-fsl-ftm driver is reasonable condense, hence
using the much faster flat regmap cache is anyway the better choice.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Stefan Agner 2016-01-20 18:56:22 -08:00 committed by Thierry Reding
parent f55532a0c0
commit ad06fdeeef
1 changed files with 1 additions and 1 deletions
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2
drivers/pwm/pwm-fsl-ftm.c
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@ -392,7 +392,7 @@ static const struct regmap_config fsl_pwm_regmap_config = {
.max_register = FTM_PWMLOAD, .max_register = FTM_PWMLOAD,
.volatile_reg = fsl_pwm_volatile_reg, .volatile_reg = fsl_pwm_volatile_reg,
.cache_type = REGCACHE_RBTREE, .cache_type = REGCACHE_FLAT,
}; };
static int fsl_pwm_probe(struct platform_device *pdev) static int fsl_pwm_probe(struct platform_device *pdev)