From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Vijayakannan Ayyathurai <vijayakannan.ayyathurai@intel.com>,
Thierry Reding <thierry.reding@gmail.com>
Cc: kbuild-all@lists.01.org,
Linux Memory Management List <linux-mm@kvack.org>,
"Lai, Poey Seng" <poey.seng.lai@intel.com>,
"Vineetha G. Jaya Kumaran" <vineetha.g.jaya.kumaran@intel.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
linux-kernel@vger.kernel.org, kernel@pengutronix.de,
kernel test robot <lkp@intel.com>
Subject: [PATCH RFC] pwm: keembay: Fix build failure with -Os
Date: Mon, 16 Nov 2020 10:08:04 +0100 [thread overview]
Message-ID: <20201116090804.206286-1-u.kleine-koenig@pengutronix.de> (raw)
In-Reply-To: <202011160303.qi5aRChY-lkp@intel.com>
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>
---
Hello,
I'm not sure this is the right fix. Maybe the bitfield stuff can be
changed somehow to make this problem go away, too?
Best regards
Uwe
drivers/pwm/pwm-keembay.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/pwm/pwm-keembay.c b/drivers/pwm/pwm-keembay.c
index 2b6dd070daa4..cdfdef66ff8e 100644
--- a/drivers/pwm/pwm-keembay.c
+++ b/drivers/pwm/pwm-keembay.c
@@ -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);
--
2.28.0
next parent reply other threads:[~2020-11-16 9:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <202011160303.qi5aRChY-lkp@intel.com>
2020-11-16 9:08 ` Uwe Kleine-König [this message]
2020-11-17 17:29 ` [PATCH RFC] pwm: keembay: Fix build failure with -Os Ayyathurai, Vijayakannan
2020-11-18 9:48 ` Uwe Kleine-König
2020-11-18 10:06 ` Uwe Kleine-König
2020-11-18 17:41 ` Ayyathurai, Vijayakannan
2020-11-18 18:01 ` Thierry Reding
2020-11-18 18:00 ` Thierry Reding
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