Re: [PATCH 04/12] tty: serial: samsung: Init USI to keep clocks running
From: Krzysztof Kozlowski
Date: Tue Aug 03 2021 - 03:37:55 EST
On 03/08/2021 01:06, Sam Protsenko wrote:
(...)
>>> diff --git a/include/linux/serial_s3c.h b/include/linux/serial_s3c.h
>>> index f6c3323fc4c5..013c2646863e 100644
>>> --- a/include/linux/serial_s3c.h
>>> +++ b/include/linux/serial_s3c.h
>>> @@ -28,6 +28,15 @@
>>> #define S3C2410_UFSTAT (0x18)
>>> #define S3C2410_UMSTAT (0x1C)
>>>
>>> +/* USI Control Register offset */
>>> +#define USI_CON (0xC4)
>>> +/* USI Option Register offset */
>>> +#define USI_OPTION (0xC8)
>>> +/* USI_CON[0] = 0b0: clear USI global software reset (Active High) */
>>> +#define USI_RESET (0<<0)
>>
>> Just 0x0. I understand you wanted to hint it is a bit field, but the
>> shift of 0 actually creates more questions.
>>
>
> After some consideration I decided to adhere to existing style and do
> something like this (in v2):
>
> 8<--------------------------------------------------------------------->8
> #define USI_CON (0xC4)
> #define USI_OPTION (0xC8)
>
> #define USI_CON_RESET_CLEAR (0<<0)
> #define USI_CON_RESET_SET (1<<0)
> #define USI_CON_RESET_MASK (1<<0)
>
> #define USI_OPTION_HWACG_CLKREQ_ON (1<<1)
> #define USI_OPTION_HWACG_CLKSTOP_ON (1<<2)
> #define USI_OPTION_HWACG_MASK (3<<1)
> 8<--------------------------------------------------------------------->8
>
> The whole reason for those comments was missing public TRM. But in the
> end I decided it just looks ugly. Also, this way I can do RMW
> operation (discussed above) in more logical way.
>
> Please let me know if code snippets above look good to you.
Please skip the USI_CON_RESET_CLEAR. There is no such pattern in the
code. Clearing bit is an obvious operation and such code is already
everywhere:
val &= ~USI_CON_RESET
(or &= ~USI_RESET_MASK)
Therefore for USI_CON_RESET only:
#define USI_CON_RESET (1<<0)
#define USI_CON_RESET_MASK (1<<0)
Best regards,
Krzysztof