linux-kernel - Re: [PATCH V7 1/6] clk: imx6sl: Use BIT(x) to avoid shifting signed 32-bit value by 31 bits

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Date:   Wed, 29 Jul 2020 17:30:28 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Anson Huang <anson.huang@....com>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Aisheng Dong <aisheng.dong@....com>,
        "arnd@...db.de" <arnd@...db.de>, Peng Fan <peng.fan@....com>,
        Abel Vesa <abel.vesa@....com>, Andy Duan <fugang.duan@....com>,
        Daniel Baluta <daniel.baluta@....com>,
        "yuehaibing@...wei.com" <yuehaibing@...wei.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Cc:     dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH V7 1/6] clk: imx6sl: Use BIT(x) to avoid shifting signed
 32-bit value by 31 bits

On 7/29/20 4:51 PM, Anson Huang wrote:
> Hi, Randy
> 
> 
>> Subject: Re: [PATCH V7 1/6] clk: imx6sl: Use BIT(x) to avoid shifting signed
>> 32-bit value by 31 bits
>>
>> On 7/29/20 7:48 AM, Anson Huang wrote:
>>> Use readl_relaxed() instead of __raw_readl(), and use BIT(x) instead
>>> of (1 << X) to fix below build warning reported by kernel test robot:
>>>
>>> drivers/clk/imx/clk-imx6sl.c:149:49: warning: Shifting signed 32-bit
>>> value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
>>>      while (!(__raw_readl(anatop_base + PLL_ARM) &
>> BM_PLL_ARM_LOCK))
>>>
>>> Signed-off-by: Anson Huang <Anson.Huang@....com>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> ---
>>> Changes since V6:
>>> 	- improve the subject.
>>> ---
>>>  drivers/clk/imx/clk-imx6sl.c | 15 ++++++++-------
>>>  1 file changed, 8 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/clk/imx/clk-imx6sl.c
>>> b/drivers/clk/imx/clk-imx6sl.c index 0f647d1..e69dba1 100644
>>> --- a/drivers/clk/imx/clk-imx6sl.c
>>> +++ b/drivers/clk/imx/clk-imx6sl.c
>>> @@ -3,6 +3,7 @@
>>>   * Copyright 2013-2014 Freescale Semiconductor, Inc.
>>>   */
>>>
>>> +#include <linux/bitfield.h>
>>
>> Hi,
>> I think you want
>> #include <linux/bits.h>
>>
>> for BIT() usage.
> 
> Actually, the linux/of.h already includes linux/bitops.h and linux/bitops.h includes
> linux/bits.h, so I will just drop linux/bitfield.h and send a V8.

or you could read Documentation/process/submit-checklist.rst,
where rule #1 says:

1) If you use a facility then #include the file that defines/declares
   that facility.  Don't depend on other header files pulling in ones
   that you use.


-- 
~Randy