Re: [PATCH v8 3/3] mmc: Add driver for LiteX's LiteSDCard interface

["Gabriel L. Somlo" <gsomlo@gmail.com>]

On Sat, Jan 08, 2022 at 01:26:08PM +0200, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 3:57 AM Gabriel L. Somlo <gsomlo@gmail.com> wrote:
> > On Sat, Jan 08, 2022 at 01:54:07AM +0200, Andy Shevchenko wrote:
> > > On Saturday, January 8, 2022, Gabriel Somlo <gsomlo@gmail.com> wrote:
> 
> > >     +       u32 div;
> > >     +
> > >     +       div = freq ? host->ref_clk / freq : 256U;
> > >
> > >     +       div = roundup_pow_of_two(div);
> > >     +       div = clamp(div, 2U, 256U);
> > >
> > > Logically seems to me that you may join these two together, because clamped
> > > range is power-of-2 one.
> >
> > `div` needs to be a power-of-2 when written to the LITEX_PHY_CLOCKERDIV
> > register (below). And clamp() will just enforce a min/max range, so if
> > (div = ref_clk / freq) ends up e.g., 5, I need both roundup_pow_of_two()
> > to bump it to 8, and clamp() to enforce that it's between 2 and 256.
> >
> > Unless you mean I should simply write it like:
> >
> >         div = clamp(roundup_pow_of_two(div), 2U, 256U);
> >
> > ... as a single line?
> 
> Yes, that's what I meant.

Turns out, clamp really hates being passed roundup_pow_of_two()
directly (see below). I think it's probably better if we leave
them as-is, to avoid going the explicit cast route which Geert
recommended against.

I'll send out v9 later today with everything else, including
devm_add_action_or_reset().

Thanks,
--Gabriel

drivers/mmc/host/litex_mmc.c: In function 'litex_mmc_setclk':
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:52:25: note: in expansion of macro '__careful_cmp'
   52 | #define max(x, y)       __careful_cmp(x, y, >)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:45: note: in expansion of macro 'max'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                                             ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~
In file included from ./include/linux/bits.h:5,
                 from drivers/mmc/host/litex_mmc.c:12:
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/const.h:12:55: note: in definition of macro '__is_constexpr'
   12 |         (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
      |                                                       ^
./include/linux/minmax.h:26:39: note: in expansion of macro '__no_side_effects'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                                       ^~~~~~~~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:52:25: note: in expansion of macro '__careful_cmp'
   52 | #define max(x, y)       __careful_cmp(x, y, >)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:45: note: in expansion of macro 'max'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                                             ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~
In file included from ./include/linux/kernel.h:17,
                 from ./include/linux/clk.h:13,
                 from drivers/mmc/host/litex_mmc.c:13:
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:28:27: note: in definition of macro '__cmp'
   28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
      |                           ^
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:52:25: note: in expansion of macro '__careful_cmp'
   52 | #define max(x, y)       __careful_cmp(x, y, >)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:45: note: in expansion of macro 'max'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                                             ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:28:40: note: in definition of macro '__cmp'
   28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
      |                                        ^
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:52:25: note: in expansion of macro '__careful_cmp'
   52 | #define max(x, y)       __careful_cmp(x, y, >)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:45: note: in expansion of macro 'max'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                                             ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:31:24: note: in definition of macro '__cmp_once'
   31 |                 typeof(x) unique_x = (x);               \
      |                        ^
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:52:25: note: in expansion of macro '__careful_cmp'
   52 | #define max(x, y)       __careful_cmp(x, y, >)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:45: note: in expansion of macro 'max'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                                             ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:31:39: note: in definition of macro '__cmp_once'
   31 |                 typeof(x) unique_x = (x);               \
      |                                       ^
./include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:28: note: in expansion of macro 'min'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                            ^~~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:52:25: note: in expansion of macro '__careful_cmp'
   52 | #define max(x, y)       __careful_cmp(x, y, >)
      |                         ^~~~~~~~~~~~~
./include/linux/minmax.h:89:45: note: in expansion of macro 'max'
   89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
      |                                             ^~~
drivers/mmc/host/litex_mmc.c:448:15: note: in expansion of macro 'clamp'
  448 |         div = clamp(roundup_pow_of_two(div), 2U, 256U);
      |               ^~~~~