linux-kernel - Re: [PATCH] clk: qcom: clk-alpha-pll: Replace divide operator with comparison

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <a995743c-f208-4afc-95da-449fdc7fab2b@quicinc.com>
Date: Fri, 30 Aug 2024 11:03:28 +0530
From: Satya Priya Kakitapalli <quic_skakitap@...cinc.com>
To: Jon Hunter <jonathanh@...dia.com>,
        Vladimir Zapolskiy
	<vladimir.zapolskiy@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Ajit Pandey <quic_ajipan@...cinc.com>,
        "Imran
 Shaik" <quic_imrashai@...cinc.com>,
        Taniya Das <quic_tdas@...cinc.com>,
        Jagadeesh Kona <quic_jkona@...cinc.com>,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...aro.org>,
        "linux-tegra@...r.kernel.org"
	<linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] clk: qcom: clk-alpha-pll: Replace divide operator with
 comparison

Hi Jon,


On 8/28/2024 7:17 PM, Jon Hunter wrote:
> Hi Satya, Vladimir,
>
> On 13/08/2024 21:01, Vladimir Zapolskiy wrote:
>> On 8/13/24 12:40, Satya Priya Kakitapalli wrote:
>>> In zonda_pll_adjust_l_val() replace the divide operator with comparison
>>> operator since comparisons are faster than divisions.
>>>
>>> Fixes: f4973130d255 ("clk: qcom: clk-alpha-pll: Update set_rate for 
>>> Zonda PLL")
>>
>> Apparently the change is not a fix, therefore I believe the Fixes tag
>> shall be removed.
>
>
> From the commit message it is not clear that this is a fix, but I
> believe that it is. With the current -next I am seeing the following
> build error (with GCC 7.3.1) on ARM ...
>
> drivers/clk/qcom/clk-alpha-pll.o: In function `clk_zonda_pll_set_rate':
> clk-alpha-pll.c:(.text+0x45dc): undefined reference to `__aeabi_uldivmod'
>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
>>> Closes: https://lore.kernel.org/r/202408110724.8pqbpDiD-lkp@intel.com/
>
> There is also the above smatch warning that was reported.
>
>>> Signed-off-by: Satya Priya Kakitapalli <quic_skakitap@...cinc.com>
>>> ---
>>>   drivers/clk/qcom/clk-alpha-pll.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/clk/qcom/clk-alpha-pll.c 
>>> b/drivers/clk/qcom/clk-alpha-pll.c
>>> index 2f620ccb41cb..fd8a82bb3690 100644
>>> --- a/drivers/clk/qcom/clk-alpha-pll.c
>>> +++ b/drivers/clk/qcom/clk-alpha-pll.c
>>> @@ -2126,7 +2126,7 @@ static void zonda_pll_adjust_l_val(unsigned 
>>> long rate, unsigned long prate, u32
>>>       remainder = do_div(quotient, prate);
>>>       *l = quotient;
>>
>> Since it's not a fix, but a simplification, you may wish to remove
>> an unnecessary 'quotient' local variable:
>>
>> remainder = do_div(rate, prate);
>>
>>> -    if ((remainder * 2) / prate)
>>> +    if ((remainder * 2) >= prate)
>>>           *l = *l + 1;
>>
>> *l = rate + (u32)(remainder * 2 >= prate);
>
>
> The above change does fix this build error for me.
>
> Satya, did you intend this to be a fix? Can we get this into -next?
>

Yes, I have posted a v2 for this last week, but there are few open 
comments on that, I'll address them and post V3 including the build 
error you reported in commit-text.


[v2] 
https://lore.kernel.org/linux-clk/20240814102005.33493-1-quic_skakitap@quicinc.com/


Thanks,

Satya Priya