[PATCH 1/1] clk: kendryte/pll.h: do not redefine nop()

[Heinrich Schuchardt]

On 03.08.20 12:10, Sean Anderson wrote:
> On 8/2/20 11:29 PM, Bin Meng wrote:
>> On Tue, Jul 28, 2020 at 11:52 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>>
>>> The kendryte PLL code uses nop as barrier. The macro is not defined for
>>> the sandbox on x86 but is defined on RISC-V.
>>
>> Is this kendryte PLL driver built for Sandbox?
>
> Yes. I added a unit test for the parameter calculation function.
>
>>
>>>
>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>> ---
>>>  include/kendryte/pll.h | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/include/kendryte/pll.h b/include/kendryte/pll.h
>>> index c8e3200799..55a40b9c97 100644
>>> --- a/include/kendryte/pll.h
>>> +++ b/include/kendryte/pll.h
>>> @@ -7,6 +7,7 @@
>>>
>>>  #include <clk.h>
>>>  #include <test/export.h>
>>> +#include <asm/io.h>
>>>
>>>  #define K210_PLL_CLKR GENMASK(3, 0)
>>>  #define K210_PLL_CLKF GENMASK(9, 4)
>>> @@ -43,9 +44,13 @@ struct k210_pll_config {
>>>  #ifdef CONFIG_UNIT_TEST
>>>  TEST_STATIC int k210_pll_calc_config(u32 rate, u32 rate_in,
>>>                                      struct k210_pll_config *best);
>>> +
>>> +#ifndef nop
>>>  #define nop()
>>>  #endif
>>
>> Maybe we can fix the kendryte PLL driver to use:
>>
>> asm volatile ("nop");
>
> Is that preferred over the nop macro?

On RISC-V nop is just a synonym for addi x0, x0, 0.

The only use of the nop statements is to guarantee a minimum time that
the reset signal is set in k210_pll_enable(). Would udelay(1); be a
valid replacement here?

Best regards

Heinrich