From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: "Ayyathurai, Vijayakannan" <vijayakannan.ayyathurai@intel.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
"kbuild-all@lists.01.org" <kbuild-all@lists.01.org>,
lkp <lkp@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
"Lai, Poey Seng" <poey.seng.lai@intel.com>
Subject: Re: [PATCH RFC] pwm: keembay: Fix build failure with -Os
Date: Wed, 18 Nov 2020 10:48:23 +0100 [thread overview]
Message-ID: <20201118094823.3a4usmbzvkbeaavg@pengutronix.de> (raw)
In-Reply-To: <DM6PR11MB4250E11A47E3B45FE0BEDC26FBE20@DM6PR11MB4250.namprd11.prod.outlook.com>
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On Tue, Nov 17, 2020 at 05:29:01PM +0000, Ayyathurai, Vijayakannan wrote:
> Hi Uwe,
>
> > From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > Sent: Monday, 16 November, 2020 5:08 PM
> > Subject: [PATCH RFC] pwm: keembay: Fix build failure with -Os
> >
> > 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>
>
> Thank you for spending time in resolving this build failure.
>
> I shall prepare and share the next version of patch with your approach.
I don't understand this last sentence. IMHO there is currently nothing
you have to do for this problem. You can send an Ack however if you want
to.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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next prev parent reply other threads:[~2020-11-18 9:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-15 19:58 [linux-next:master 4911/5794] include/linux/bitfield.h:119:3: error: call to '__bad_mask' declared with attribute error: bad bitfield mask kernel test robot
2020-11-16 9:08 ` [PATCH RFC] pwm: keembay: Fix build failure with -Os Uwe Kleine-König
2020-11-17 17:29 ` Ayyathurai, Vijayakannan
2020-11-18 9:48 ` Uwe Kleine-König [this message]
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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