diff mbox series

[v8,4/4] gpio: xilinx: Utilize for_each_set_clump macro

Message ID 46c05c5deeada60a13ee0de83c68583d578f42fd.1592224129.git.syednwaris@gmail.com
State New
Headers show
Series Introduce the for_each_set_clump macro | expand

Commit Message

Syed Nayyar Waris June 15, 2020, 12:54 p.m. UTC 
This patch reimplements the xgpio_set_multiple function in
drivers/gpio/gpio-xilinx.c to use the new for_each_set_clump macro.
Instead of looping for each bit in xgpio_set_multiple
function, now we can check each channel at a time and save cycles.

Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
Changes in v8:
 - No change.

Changes in v7:
 - No change.

Changes in v6:
 - No change.

Changes in v5:
 - Minor change: Inline values '32' and '64' in code for better
   code readability.

Changes in v4:
 - Minor change: Inline values '32' and '64' in code for better
   code readability.

Changes in v3:
 - No change.

Changes in v2:
 - No change.

 drivers/gpio/gpio-xilinx.c | 62 ++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 30 deletions(-)

Comments

kernel test robot June 15, 2020, 8:09 p.m. UTC | #1 
Hi Syed,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on 444fc5cde64330661bf59944c43844e7d4c2ccd8]

url:    https://github.com/0day-ci/linux/commits/Syed-Nayyar-Waris/Introduce-the-for_each_set_clump-macro/20200615-205729
base:    444fc5cde64330661bf59944c43844e7d4c2ccd8
config: sparc64-randconfig-s032-20200615 (attached as .config)
compiler: sparc64-linux-gcc (GCC) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.2-rc1-3-g55607964-dirty
        # save the attached .config to linux build tree
        make W=1 C=1 ARCH=sparc64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)

>> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
   include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
>> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)

vim +639 include/linux/bitmap.h

169c474fb22d8a William Breathitt Gray 2019-12-04  613  
803024b6c8a375 Syed Nayyar Waris      2020-06-15  614  /**
803024b6c8a375 Syed Nayyar Waris      2020-06-15  615   * bitmap_set_value - set n-bit value within a memory region
803024b6c8a375 Syed Nayyar Waris      2020-06-15  616   * @map: address to the bitmap memory region
803024b6c8a375 Syed Nayyar Waris      2020-06-15  617   * @value: value of nbits
803024b6c8a375 Syed Nayyar Waris      2020-06-15  618   * @start: bit offset of the n-bit value
803024b6c8a375 Syed Nayyar Waris      2020-06-15  619   * @nbits: size of value in bits
803024b6c8a375 Syed Nayyar Waris      2020-06-15  620   */
803024b6c8a375 Syed Nayyar Waris      2020-06-15  621  static inline void bitmap_set_value(unsigned long *map,
803024b6c8a375 Syed Nayyar Waris      2020-06-15  622  				    unsigned long value,
803024b6c8a375 Syed Nayyar Waris      2020-06-15  623  				    unsigned long start, unsigned long nbits)
803024b6c8a375 Syed Nayyar Waris      2020-06-15  624  {
803024b6c8a375 Syed Nayyar Waris      2020-06-15  625  	const size_t index = BIT_WORD(start);
803024b6c8a375 Syed Nayyar Waris      2020-06-15  626  	const unsigned long offset = start % BITS_PER_LONG;
803024b6c8a375 Syed Nayyar Waris      2020-06-15  627  	const unsigned long ceiling = roundup(start + 1, BITS_PER_LONG);
803024b6c8a375 Syed Nayyar Waris      2020-06-15  628  	const unsigned long space = ceiling - start;
803024b6c8a375 Syed Nayyar Waris      2020-06-15  629  
803024b6c8a375 Syed Nayyar Waris      2020-06-15  630  	value &= GENMASK(nbits - 1, 0);
803024b6c8a375 Syed Nayyar Waris      2020-06-15  631  
803024b6c8a375 Syed Nayyar Waris      2020-06-15  632  	if (space >= nbits) {
803024b6c8a375 Syed Nayyar Waris      2020-06-15  633  		map[index] &= ~(GENMASK(nbits + offset - 1, offset));
803024b6c8a375 Syed Nayyar Waris      2020-06-15  634  		map[index] |= value << offset;
803024b6c8a375 Syed Nayyar Waris      2020-06-15  635  	} else {
803024b6c8a375 Syed Nayyar Waris      2020-06-15  636  		map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
803024b6c8a375 Syed Nayyar Waris      2020-06-15  637  		map[index] |= value << offset;
803024b6c8a375 Syed Nayyar Waris      2020-06-15 @638  		map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
803024b6c8a375 Syed Nayyar Waris      2020-06-15 @639  		map[index + 1] |= (value >> space);
803024b6c8a375 Syed Nayyar Waris      2020-06-15  640  	}
803024b6c8a375 Syed Nayyar Waris      2020-06-15  641  }
803024b6c8a375 Syed Nayyar Waris      2020-06-15  642  

:::::: The code at line 639 was first introduced by commit
:::::: 803024b6c8a375ba9e9e9467595d7d52d4f6a38e bitops: Introduce the for_each_set_clump macro

:::::: TO: Syed Nayyar Waris <syednwaris@gmail.com>
:::::: CC: 0day robot <lkp@intel.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Syed Nayyar Waris June 16, 2020, 5:57 a.m. UTC | #2 
On Tue, Jun 16, 2020 at 1:39 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Syed,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on 444fc5cde64330661bf59944c43844e7d4c2ccd8]
>
> url:    https://github.com/0day-ci/linux/commits/Syed-Nayyar-Waris/Introduce-the-for_each_set_clump-macro/20200615-205729
> base:    444fc5cde64330661bf59944c43844e7d4c2ccd8
> config: sparc64-randconfig-s032-20200615 (attached as .config)
> compiler: sparc64-linux-gcc (GCC) 9.3.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.2-rc1-3-g55607964-dirty
>         # save the attached .config to linux build tree
>         make W=1 C=1 ARCH=sparc64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
>
> sparse warnings: (new ones prefixed by >>)
>
> >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>    include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
> >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> >> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)
>
> vim +639 include/linux/bitmap.h
>
> 169c474fb22d8a William Breathitt Gray 2019-12-04  613
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  614  /**
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  615   * bitmap_set_value - set n-bit value within a memory region
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  616   * @map: address to the bitmap memory region
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  617   * @value: value of nbits
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  618   * @start: bit offset of the n-bit value
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  619   * @nbits: size of value in bits
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  620   */
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  621  static inline void bitmap_set_value(unsigned long *map,
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  622                               unsigned long value,
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  623                               unsigned long start, unsigned long nbits)
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  624  {
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  625   const size_t index = BIT_WORD(start);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  626   const unsigned long offset = start % BITS_PER_LONG;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  627   const unsigned long ceiling = roundup(start + 1, BITS_PER_LONG);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  628   const unsigned long space = ceiling - start;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  629
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  630   value &= GENMASK(nbits - 1, 0);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  631
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  632   if (space >= nbits) {
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  633           map[index] &= ~(GENMASK(nbits + offset - 1, offset));
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  634           map[index] |= value << offset;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  635   } else {
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  636           map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  637           map[index] |= value << offset;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @638           map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @639           map[index + 1] |= (value >> space);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  640   }
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  641  }
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  642


Regarding the compilation warning reported above:

"sparse: shift too big (64) for type unsigned long" at line 639
"sparse: invalid access past the end of 'old' (8 8)" at line 638

Kindly refer to the code above, at these line numbers.

I am in the process of fixing this warning. But what would be the fix
? At the moment can't think of a code-fix to make the compilation
warning disappear (specially at line 639). Can anyone please explain
to me the meaning of the compilation warning more deeply?

By the way, this warning was not reported in (earlier) v7 of the patchset.

Regards
Syed Nayyar Waris
Syed Nayyar Waris June 19, 2020, 7 a.m. UTC | #3 
>
> Hi Syed,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on 444fc5cde64330661bf59944c43844e7d4c2ccd8]
>
> url:    https://github.com/0day-ci/linux/commits/Syed-Nayyar-Waris/Introduce-the-for_each_set_clump-macro/20200615-205729
> base:    444fc5cde64330661bf59944c43844e7d4c2ccd8
> config: sparc64-randconfig-s032-20200615 (attached as .config)
> compiler: sparc64-linux-gcc (GCC) 9.3.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.2-rc1-3-g55607964-dirty
>         # save the attached .config to linux build tree
>         make W=1 C=1 ARCH=sparc64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
>

>
>
> sparse warnings: (new ones prefixed by >>)
>
> >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
>    include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
> >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> >> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)
>

Hi All,

It seems to me that to reproduce this warning, I have to use the
sparc64 compiler. I have installed 'sparc64-linux-gnu-gcc' on my
computer.
I have to specify that this compiler needs to be used for build
process. How/ Where do I specify this?

I have downloaded the config.gz (has config file) and placed it at the
root of the linux kernel project tree. But the Makefile STILL has
'gcc' as the compiler. When I build, it is the 'gcc' compiler being
used and not 'sparc64-linux-gnu-gcc'. I know I can manually change the
Makefile to use sparc64 compiler, but I think there must be some more
elegant way to do this, perhaps using make menuconfig?

Kindly illuminate as to how shall I reproduce the compiler warning.

Regards
Syed Nayyar Waris

> vim +639 include/linux/bitmap.h
>
> 169c474fb22d8a William Breathitt Gray 2019-12-04  613
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  614  /**
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  615   * bitmap_set_value - set n-bit value within a memory region
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  616   * @map: address to the bitmap memory region
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  617   * @value: value of nbits
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  618   * @start: bit offset of the n-bit value
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  619   * @nbits: size of value in bits
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  620   */
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  621  static inline void bitmap_set_value(unsigned long *map,
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  622                               unsigned long value,
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  623                               unsigned long start, unsigned long nbits)
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  624  {
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  625   const size_t index = BIT_WORD(start);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  626   const unsigned long offset = start % BITS_PER_LONG;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  627   const unsigned long ceiling = roundup(start + 1, BITS_PER_LONG);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  628   const unsigned long space = ceiling - start;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  629
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  630   value &= GENMASK(nbits - 1, 0);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  631
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  632   if (space >= nbits) {
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  633           map[index] &= ~(GENMASK(nbits + offset - 1, offset));
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  634           map[index] |= value << offset;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  635   } else {
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  636           map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  637           map[index] |= value << offset;
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @638           map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @639           map[index + 1] |= (value >> space);
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  640   }
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  641  }
> 803024b6c8a375 Syed Nayyar Waris      2020-06-15  642
>
> :::::: The code at line 639 was first introduced by commit
> :::::: 803024b6c8a375ba9e9e9467595d7d52d4f6a38e bitops: Introduce the for_each_set_clump macro
>
> :::::: TO: Syed Nayyar Waris <syednwaris@gmail.com>
Andy Shevchenko June 19, 2020, 8:38 a.m. UTC | #4 
On Fri, Jun 19, 2020 at 10:02 AM Syed Nayyar Waris <syednwaris@gmail.com> wrote:

...

> > config: sparc64-randconfig-s032-20200615 (attached as .config)
> > compiler: sparc64-linux-gcc (GCC) 9.3.0
> > reproduce:
> >         # apt-get install sparse
> >         # sparse version: v0.6.2-rc1-3-g55607964-dirty
> >         # save the attached .config to linux build tree
> >         make W=1 C=1 ARCH=sparc64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'

...

> > sparse warnings: (new ones prefixed by >>)
> >
> > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> >    include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
> > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > >> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)

> It seems to me that to reproduce this warning, I have to use the
> sparc64 compiler. I have installed 'sparc64-linux-gnu-gcc' on my
> computer.

Sparse is not a compiler.

> I have to specify that this compiler needs to be used for build
> process. How/ Where do I specify this?
>
> I have downloaded the config.gz (has config file) and placed it at the
> root of the linux kernel project tree. But the Makefile STILL has
> 'gcc' as the compiler. When I build, it is the 'gcc' compiler being
> used and not 'sparc64-linux-gnu-gcc'. I know I can manually change the
> Makefile to use sparc64 compiler, but I think there must be some more
> elegant way to do this, perhaps using make menuconfig?

If you wish to run a compilation, download a compiler from [1], and,
after adding its bin/ folder to PATH, run
make CROSS_COMPILE=sparc64-linux- ARCH=sparc64 ... # first generate .config

> Kindly illuminate as to how shall I reproduce the compiler warning.

> > 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @638           map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
> > 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @639           map[index + 1] |= (value >> space);

Hmm... I think I sent a reply [2] where I explained how space can be
64. Do you agree with analysis?

[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
[2]: https://lore.kernel.org/lkml/20200616081428.GP2428291@smile.fi.intel.com/
Andy Shevchenko June 19, 2020, 9:05 a.m. UTC | #5 
On Fri, Jun 19, 2020 at 11:38:59AM +0300, Andy Shevchenko wrote:
> On Fri, Jun 19, 2020 at 10:02 AM Syed Nayyar Waris <syednwaris@gmail.com> wrote:
> 
> ...
> 
> > > config: sparc64-randconfig-s032-20200615 (attached as .config)
> > > compiler: sparc64-linux-gcc (GCC) 9.3.0
> > > reproduce:
> > >         # apt-get install sparse
> > >         # sparse version: v0.6.2-rc1-3-g55607964-dirty
> > >         # save the attached .config to linux build tree
> > >         make W=1 C=1 ARCH=sparc64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
> 
> ...
> 
> > > sparse warnings: (new ones prefixed by >>)
> > >
> > > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > >    include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
> > > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > > >> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)
> 
> > It seems to me that to reproduce this warning, I have to use the
> > sparc64 compiler. I have installed 'sparc64-linux-gnu-gcc' on my
> > computer.
> 
> Sparse is not a compiler.

On x86_64:

  CHECK   drivers/gpio/gpio-xilinx.c
  include/linux/bitmap.h:639:45: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:639:45: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:594:63: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:639:45: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:638:17: warning: invalid access past the end of 'old' (8 8)

> > I have to specify that this compiler needs to be used for build
> > process. How/ Where do I specify this?
> >
> > I have downloaded the config.gz (has config file) and placed it at the
> > root of the linux kernel project tree. But the Makefile STILL has
> > 'gcc' as the compiler. When I build, it is the 'gcc' compiler being
> > used and not 'sparc64-linux-gnu-gcc'. I know I can manually change the
> > Makefile to use sparc64 compiler, but I think there must be some more
> > elegant way to do this, perhaps using make menuconfig?
> 
> If you wish to run a compilation, download a compiler from [1], and,
> after adding its bin/ folder to PATH, run
> make CROSS_COMPILE=sparc64-linux- ARCH=sparc64 ... # first generate .config
> 
> > Kindly illuminate as to how shall I reproduce the compiler warning.
> 
> > > 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @638           map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
> > > 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @639           map[index + 1] |= (value >> space);
> 
> Hmm... I think I sent a reply [2] where I explained how space can be
> 64. Do you agree with analysis?
> 
> [1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
> [2]: https://lore.kernel.org/lkml/20200616081428.GP2428291@smile.fi.intel.com/
Luc Van Oostenryck June 19, 2020, 2:26 p.m. UTC | #6 
On Tue, Jun 16, 2020 at 11:27:18AM +0530, Syed Nayyar Waris wrote:

Hi, 

> Regarding the compilation warning reported above:
> 
> "sparse: shift too big (64) for type unsigned long" at line 639
> "sparse: invalid access past the end of 'old' (8 8)" at line 638
> 
> Kindly refer to the code above, at these line numbers.
> 
> I am in the process of fixing this warning. But what would be the fix?
> ? At the moment can't think of a code-fix to make the compilation
> warning disappear (specially at line 639). Can anyone please explain
> to me the meaning of the compilation warning more deeply?

This error message is caused by sparse doing the check too early.
There is thus nothing to be fixed for it in this code.

Best regards,
-- Luc
Robin Murphy June 19, 2020, 7:17 p.m. UTC | #7 
On 2020-06-15 13:54, Syed Nayyar Waris wrote:
> This patch reimplements the xgpio_set_multiple function in
> drivers/gpio/gpio-xilinx.c to use the new for_each_set_clump macro.
> Instead of looping for each bit in xgpio_set_multiple
> function, now we can check each channel at a time and save cycles.
> 
> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> Cc: Michal Simek <michal.simek@xilinx.com>
> Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> ---
> Changes in v8:
>   - No change.
> 
> Changes in v7:
>   - No change.
> 
> Changes in v6:
>   - No change.
> 
> Changes in v5:
>   - Minor change: Inline values '32' and '64' in code for better
>     code readability.
> 
> Changes in v4:
>   - Minor change: Inline values '32' and '64' in code for better
>     code readability.
> 
> Changes in v3:
>   - No change.
> 
> Changes in v2:
>   - No change.
> 
>   drivers/gpio/gpio-xilinx.c | 62 ++++++++++++++++++++------------------
>   1 file changed, 32 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-xilinx.c b/drivers/gpio/gpio-xilinx.c
> index 67f9f82e0db0..e81092dea27e 100644
> --- a/drivers/gpio/gpio-xilinx.c
> +++ b/drivers/gpio/gpio-xilinx.c
> @@ -136,39 +136,41 @@ static void xgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
>   static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
>   			       unsigned long *bits)
>   {
> -	unsigned long flags;
> +	unsigned long flags[2];
>   	struct xgpio_instance *chip = gpiochip_get_data(gc);
> -	int index = xgpio_index(chip, 0);
> -	int offset, i;
> -
> -	spin_lock_irqsave(&chip->gpio_lock[index], flags);
> -
> -	/* Write to GPIO signals */
> -	for (i = 0; i < gc->ngpio; i++) {
> -		if (*mask == 0)
> -			break;
> -		/* Once finished with an index write it out to the register */
> -		if (index !=  xgpio_index(chip, i)) {
> -			xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> -				       index * XGPIO_CHANNEL_OFFSET,
> -				       chip->gpio_state[index]);
> -			spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
> -			index =  xgpio_index(chip, i);
> -			spin_lock_irqsave(&chip->gpio_lock[index], flags);
> -		}
> -		if (__test_and_clear_bit(i, mask)) {
> -			offset =  xgpio_offset(chip, i);
> -			if (test_bit(i, bits))
> -				chip->gpio_state[index] |= BIT(offset);
> -			else
> -				chip->gpio_state[index] &= ~BIT(offset);
> -		}
> +	u32 *const state = chip->gpio_state;
> +	unsigned int *const width = chip->gpio_width;

Immutable pointers to mutable data are pretty unusual, especially for 
temporary local variables. Let me share my thought process upon seeing this:

- hmm, is "* const" simply a mistake that's meant to be "const *"?
- <scan the rest of the function> no, updating chip->gpio_state seems 
appropriate, so it can't be that.
- does anything take the address of either of these variables that might 
justify it?
- <scan the rest of the function again> nope, they're only ever used by 
value
- hmm, maybe it's just paranoia, but in that case why isn't width "const 
* const" since chip->gpio_width shouldn't need to be modified?
- hmm...

And at that point I've spent nearly a minute parsing what should have 
been be some trivial definitions of local shorthand variables. Defensive 
programming is all very well, but the distraction to readers (I can't be 
the only one) can easily outweigh any perceived value in trying to 
harden against theoretical future developer error in a straightforward 
~30-line function.

> +	unsigned long offset, clump;
> +	size_t index;
> +
> +	DECLARE_BITMAP(old, 64);
> +	DECLARE_BITMAP(new, 64);
> +	DECLARE_BITMAP(changed, 64);
> +
> +	spin_lock_irqsave(&chip->gpio_lock[0], flags[0]);
> +	spin_lock_irqsave(&chip->gpio_lock[1], flags[1]);

Why _irqsave on the inner lock? (think about it...)

> +
> +	bitmap_set_value(old, state[0], 0, width[0]);
> +	bitmap_set_value(old, state[1], width[0], width[1]);
> +	bitmap_replace(new, old, bits, mask, gc->ngpio);
> +
> +	bitmap_set_value(old, state[0], 0, 32);
> +	bitmap_set_value(old, state[1], 32, 32);
> +	state[0] = bitmap_get_value(new, 0, width[0]);
> +	state[1] = bitmap_get_value(new, width[0], width[1]);
> +	bitmap_set_value(new, state[0], 0, 32);
> +	bitmap_set_value(new, state[1], 32, 32);
> +	bitmap_xor(changed, old, new, 64);
> +
> +	for_each_set_clump(offset, clump, changed, 64, 32) {
> +		index = offset / 32;
> +		xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> +				index * XGPIO_CHANNEL_OFFSET,
> +				state[index]);
>   	}

TBH this looks like a rather overcomplicated and horribly inefficient 
way of doing:

	if (((u32 *)changed)[0])
		xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET,
				state[0]);
	if (((u32 *)changed)[1])
		xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
				XGPIO_CHANNEL_OFFSET, state[1]);

(and doing the changed/state update itself one word at a time for each 
condition would probably be a fair bit more efficient in terms of 
minimising spilling to the stack on 32-bit machines)

I can see this API having merit if the clumps are a weird size or 
expected to be significantly sparse in the bitmap, but making 
out-of-line calls to an iterator which itself involves another 
out-of-line call and an integer division, all just to process two halves 
of a 64-bit value, seems... unnecessarily silly :/

[drive-by review since I had a "packing small values into bitmaps" 
use-case and wondered if there might be anything interesting here]

Robin.

>   
> -	xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> -		       index * XGPIO_CHANNEL_OFFSET, chip->gpio_state[index]);
> -
> -	spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
> +	spin_unlock_irqrestore(&chip->gpio_lock[1], flags[1]);
> +	spin_unlock_irqrestore(&chip->gpio_lock[0], flags[0]);
>   }
>   
>   /**
>
diff mbox series

Patch

diff --git a/drivers/gpio/gpio-xilinx.c b/drivers/gpio/gpio-xilinx.c
index 67f9f82e0db0..e81092dea27e 100644
--- a/drivers/gpio/gpio-xilinx.c
+++ b/drivers/gpio/gpio-xilinx.c
@@ -136,39 +136,41 @@  static void xgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
 static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
 			       unsigned long *bits)
 {
-	unsigned long flags;
+	unsigned long flags[2];
 	struct xgpio_instance *chip = gpiochip_get_data(gc);
-	int index = xgpio_index(chip, 0);
-	int offset, i;
-
-	spin_lock_irqsave(&chip->gpio_lock[index], flags);
-
-	/* Write to GPIO signals */
-	for (i = 0; i < gc->ngpio; i++) {
-		if (*mask == 0)
-			break;
-		/* Once finished with an index write it out to the register */
-		if (index !=  xgpio_index(chip, i)) {
-			xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
-				       index * XGPIO_CHANNEL_OFFSET,
-				       chip->gpio_state[index]);
-			spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
-			index =  xgpio_index(chip, i);
-			spin_lock_irqsave(&chip->gpio_lock[index], flags);
-		}
-		if (__test_and_clear_bit(i, mask)) {
-			offset =  xgpio_offset(chip, i);
-			if (test_bit(i, bits))
-				chip->gpio_state[index] |= BIT(offset);
-			else
-				chip->gpio_state[index] &= ~BIT(offset);
-		}
+	u32 *const state = chip->gpio_state;
+	unsigned int *const width = chip->gpio_width;
+	unsigned long offset, clump;
+	size_t index;
+
+	DECLARE_BITMAP(old, 64);
+	DECLARE_BITMAP(new, 64);
+	DECLARE_BITMAP(changed, 64);
+
+	spin_lock_irqsave(&chip->gpio_lock[0], flags[0]);
+	spin_lock_irqsave(&chip->gpio_lock[1], flags[1]);
+
+	bitmap_set_value(old, state[0], 0, width[0]);
+	bitmap_set_value(old, state[1], width[0], width[1]);
+	bitmap_replace(new, old, bits, mask, gc->ngpio);
+
+	bitmap_set_value(old, state[0], 0, 32);
+	bitmap_set_value(old, state[1], 32, 32);
+	state[0] = bitmap_get_value(new, 0, width[0]);
+	state[1] = bitmap_get_value(new, width[0], width[1]);
+	bitmap_set_value(new, state[0], 0, 32);
+	bitmap_set_value(new, state[1], 32, 32);
+	bitmap_xor(changed, old, new, 64);
+
+	for_each_set_clump(offset, clump, changed, 64, 32) {
+		index = offset / 32;
+		xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
+				index * XGPIO_CHANNEL_OFFSET,
+				state[index]);
 	}
 
-	xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
-		       index * XGPIO_CHANNEL_OFFSET, chip->gpio_state[index]);
-
-	spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
+	spin_unlock_irqrestore(&chip->gpio_lock[1], flags[1]);
+	spin_unlock_irqrestore(&chip->gpio_lock[0], flags[0]);
 }
 
 /**