On Tue, Jun 09, 2020 at 04:35:17PM +0200, Krzysztof Kozlowski wrote:
> From: Stefan Agner <stefan@xxxxxxxx>
>
> commit ad06fdeeef1cbadf86ebbe510e8079abada8b44e upstream.
>
> 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@xxxxxxxx>
> Cc: Mark Brown <broonie@xxxxxxxxxx>
> Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxx>
> Signed-off-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
>
> ---
>
> Fixes lockdep warning. Apply to v4.4 and newer.
> ---
> drivers/pwm/pwm-fsl-ftm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pwm/pwm-fsl-ftm.c b/drivers/pwm/pwm-fsl-ftm.c
> index 7225ac6b3df5..fad968eb75f6 100644
> --- a/drivers/pwm/pwm-fsl-ftm.c
> +++ b/drivers/pwm/pwm-fsl-ftm.c
> @@ -392,7 +392,7 @@ static const struct regmap_config fsl_pwm_regmap_config = {
>
> .max_register = FTM_PWMLOAD,
> .volatile_reg = fsl_pwm_volatile_reg,
> - .cache_type = REGCACHE_RBTREE,
> + .cache_type = REGCACHE_FLAT,
> };
>
> static int fsl_pwm_probe(struct platform_device *pdev)
> --
> 2.17.1
>
Now queued up, thanks.
greg k-h
