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bb72e1dbae
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.