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pwm: keembay: Fix build failure with -Os

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The driver used this construct:

	#define KMB_PWM_LEADIN_MASK             GENMASK(30, 0)

	static inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
						   u32 val, u32 offset)
	{
		u32 buff = readl(priv->base + offset);

		buff = u32_replace_bits(buff, val, mask);
		writel(buff, priv->base + offset);
	}

	...
	keembay_pwm_update_bits(priv, KMB_PWM_LEADIN_MASK, 0,
					KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));

With CONFIG_CC_OPTIMIZE_FOR_SIZE the compiler (here: gcc 10.2.0) this
triggers:

	In file included from /home/uwe/gsrc/linux/drivers/pwm/pwm-keembay.c:16:
	In function ‘field_multiplier’,
	    inlined from ‘keembay_pwm_update_bits’ at /home/uwe/gsrc/linux/include/linux/bitfield.h:124:17:
	/home/uwe/gsrc/linux/include/linux/bitfield.h:119:3: error: call to ‘__bad_mask’ declared with attribute error: bad bitfield mask
	  119 |   __bad_mask();
	      |   ^~~~~~~~~~~~
	In function ‘field_multiplier’,
	    inlined from ‘keembay_pwm_update_bits’ at /home/uwe/gsrc/linux/include/linux/bitfield.h:154:1:
	/home/uwe/gsrc/linux/include/linux/bitfield.h:119:3: error: call to ‘__bad_mask’ declared with attribute error: bad bitfield mask
	  119 |   __bad_mask();
	      |   ^~~~~~~~~~~~

The compiler doesn't seem to be able to notice that with field being
0x3ffffff the expression

	if ((field | (field - 1)) & ((field | (field - 1)) + 1))
		__bad_mask();

can be optimized away.

So use __always_inline and document the problem in a comment to fix
this.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Tested-by: Vijayakannan Ayyathurai <vijayakannan.ayyathurai@intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Uwe Kleine-König 2020-11-16 10:08:04 +01:00 committed by Thierry Reding
parent 765edf0bf0
commit bb72e1dbae
1 changed files with 6 additions and 1 deletions
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7
drivers/pwm/pwm-keembay.c
View File

@ -63,7 +63,12 @@ static int keembay_clk_enable(struct device *dev, struct clk *clk)
return devm_add_action_or_reset(dev, keembay_clk_unprepare, clk);
}
static inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
/*
* With gcc 10, CONFIG_CC_OPTIMIZE_FOR_SIZE and only "inline" instead of
* "__always_inline" this fails to compile because the compiler doesn't notice
* for all valid masks (e.g. KMB_PWM_LEADIN_MASK) that they are ok.
*/
static __always_inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
u32 val, u32 offset)
{
u32 buff = readl(priv->base + offset);