[PATCH] mtd: rawnand: denali_dt: make the core clock optional

[Masahiro Yamada]

On Thu, Jan 9, 2020 at 10:20 PM Marek Vasut <marex at denx.de> wrote:
>
> On 1/9/20 1:02 PM, Masahiro Yamada wrote:
> > The "nand_x" and "ecc" clocks are currently optional. Make the core
> > clock optional in the same way. This will allow platforms with no clock
> > driver support to use this driver.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro at socionext.com>
> > ---
> >
> >  drivers/mtd/nand/raw/denali_dt.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/raw/denali_dt.c b/drivers/mtd/nand/raw/denali_dt.c
> > index 0ce81324b90e..b1e14982c443 100644
> > --- a/drivers/mtd/nand/raw/denali_dt.c
> > +++ b/drivers/mtd/nand/raw/denali_dt.c
> > @@ -91,7 +91,7 @@ static int denali_dt_probe(struct udevice *dev)
> >       if (ret)
> >               ret = clk_get_by_index(dev, 0, &clk);
> >       if (ret)
> > -             return ret;
> > +             clk.dev = NULL;
> >
> >       ret = clk_get_by_name(dev, "nand_x", &clk_x);
> >       if (ret)
> > @@ -101,9 +101,11 @@ static int denali_dt_probe(struct udevice *dev)
> >       if (ret)
> >               clk_ecc.dev = NULL;
> >
> > -     ret = clk_enable(&clk);
> > -     if (ret)
> > -             return ret;
> > +     if (clk.dev) {
> > +             ret = clk_enable(&clk);
> > +             if (ret)
> > +                     return ret;
> > +     }
> >
> >       if (clk_x.dev) {
> >               ret = clk_enable(&clk_x);
> >
>
> Why do we need any of the clock code if the clock aren't available ? It
> just takes space for no reason.

Are you sure?

The compiler optimizes the unreachable code out.


My compiler is this:

$ aarch64-linux-gnu-gcc --version
aarch64-linux-gnu-gcc (Linaro GCC 7.4-2019.02) 7.4.1 20181213
[linaro-7.4-2019.02 revision 56ec6f6b99cc167ff0c2f8e1a2eed33b1edc85d4]
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.




I compiled the denali_dt.c with CONFIG_CLK disabled
and here is the disassembly.

My patch and yours produce exactly the same code.


0000000000000000 <denali_dt_probe>:
   0: a9b97bfd stp x29, x30, [sp, #-112]!
   4: 910003fd mov x29, sp
   8: a90153f3 stp x19, x20, [sp, #16]
   c: aa0003f4 mov x20, x0
  10: f90013f5 str x21, [sp, #32]
  14: 94000000 bl 0 <dev_get_priv>
  18: aa0003f3 mov x19, x0
  1c: aa1403e0 mov x0, x20
  20: 94000000 bl 0 <dev_get_driver_data>
  24: b40000e0 cbz x0, 40 <denali_dt_probe+0x40>
  28: b9400001 ldr w1, [x0]
  2c: b9070261 str w1, [x19, #1792]
  30: b9400401 ldr w1, [x0, #4]
  34: b9070661 str w1, [x19, #1796]
  38: f9400400 ldr x0, [x0, #8]
  3c: f9038660 str x0, [x19, #1800]
  40: f9035a74 str x20, [x19, #1712]
  44: 90000001 adrp x1, 0 <denali_dt_probe>
  48: 9100e3a2 add x2, x29, #0x38
  4c: 91000021 add x1, x1, #0x0
  50: f9401680 ldr x0, [x20, #40]
  54: 94000000 bl 0 <ofnode_read_resource_byname>
  58: 350003e0 cbnz w0, d4 <denali_dt_probe+0xd4>
  5c: f9401fa0 ldr x0, [x29, #56]
  60: 90000001 adrp x1, 0 <denali_dt_probe>
  64: f9036260 str x0, [x19, #1728]
  68: 9100e3a2 add x2, x29, #0x38
  6c: 91000021 add x1, x1, #0x0
  70: f9401680 ldr x0, [x20, #40]
  74: 94000000 bl 0 <ofnode_read_resource_byname>
  78: 350002e0 cbnz w0, d4 <denali_dt_probe+0xd4>
  7c: f9401fa0 ldr x0, [x29, #56]
  80: 911ca275 add x21, x19, #0x728
  84: f9036660 str x0, [x19, #1736]
  88: 90000000 adrp x0, 0 <denali_dt_probe>
  8c: 91000000 add x0, x0, #0x0
  90: 94000000 bl 0 <printf>
  94: d29e1000 mov x0, #0xf080                // #61568
  98: aa1503e1 mov x1, x21
  9c: f2a05f40 movk x0, #0x2fa, lsl #16
  a0: f9034e60 str x0, [x19, #1688]
  a4: d2984000 mov x0, #0xc200                // #49664
  a8: f2a17d60 movk x0, #0xbeb, lsl #16
  ac: f9035260 str x0, [x19, #1696]
  b0: aa1403e0 mov x0, x20
  b4: 94000000 bl 0 <reset_get_bulk>
  b8: 34000160 cbz w0, e4 <denali_dt_probe+0xe4>
  bc: 2a0003e1 mov w1, w0
  c0: 90000000 adrp x0, 0 <denali_dt_probe>
  c4: 91000000 add x0, x0, #0x0
  c8: 94000000 bl 0 <printf>
  cc: aa1303e0 mov x0, x19
  d0: 94000000 bl 0 <denali_init>
  d4: a94153f3 ldp x19, x20, [sp, #16]
  d8: f94013f5 ldr x21, [sp, #32]
  dc: a8c77bfd ldp x29, x30, [sp], #112
  e0: d65f03c0 ret
  e4: aa1503e0 mov x0, x21
  e8: 94000000 bl 0 <reset_deassert_bulk>
  ec: 17fffff8 b cc <denali_dt_probe+0xcc>





-- 
Best Regards
Masahiro Yamada