linux-kernel - Re: [PATCH V3 2/4] soc/tegra: pmc: Correct type of variable for tegra_pmc

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Date:	Thu, 5 May 2016 18:05:07 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Jon Hunter <jonathanh@...dia.com>, <thierry.reding@...il.com>,
	<swarren@...dotorg.org>, <airlied@...ux.ie>
CC:	<gnurou@...il.com>, <dri-devel@...ts.freedesktop.org>,
	<linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 2/4] soc/tegra: pmc: Correct type of variable for tegra_pmc_readl()


On Thursday 05 May 2016 06:13 PM, Jon Hunter wrote:
> On 05/05/16 10:52, Laxman Dewangan wrote:
>> On Thursday 05 May 2016 03:19 PM, Jon Hunter wrote:
>>> On 04/05/16 12:39, Laxman Dewangan wrote:
>>>> The function tegra_pmc_readl() returns the u32 type data and hence
>>>> change the data type of variable where this data is stored to u32
>>>> type.
>>>>
>>>> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
>>>>
>>>> ---
>>>> Changes from V1:
>>>> -This is new in series as per discussion on V1 series to use u32 for
>>>> tegra_pmc_readl.
>>>>
>>>> Changes from V2:
>>>> - Make unsigned long to u32 for some missed variable from V1.
>>>> ---
>>>>    drivers/soc/tegra/pmc.c | 24 ++++++++++++++----------
>>>>    1 file changed, 14 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
>>>> index 2c3f1f9..eff9425 100644
>>>> --- a/drivers/soc/tegra/pmc.c
>>>> +++ b/drivers/soc/tegra/pmc.c
>>>> @@ -844,7 +844,8 @@ static void tegra_powergate_init(struct tegra_pmc
>>>> *pmc)
>>>>    static int tegra_io_rail_prepare(unsigned int id, unsigned long
>>>> *request,
>>>>                     unsigned long *status, unsigned int *bit)
>>>>    {
>>>> -    unsigned long rate, value;
>>>> +    unsigned long rate;
>>>> +    u32 value;
>>>>          *bit = id % 32;
>>>>    @@ -868,17 +869,18 @@ static int tegra_io_rail_prepare(unsigned int
>>>> id, unsigned long *request,
>>>>        tegra_pmc_writel(DPD_SAMPLE_ENABLE, DPD_SAMPLE);
>>>>          /* must be at least 200 ns, in APB (PCLK) clock cycles */
>>>> -    value = DIV_ROUND_UP(1000000000, rate);
>>>> -    value = DIV_ROUND_UP(200, value);
>>>> +    rate = DIV_ROUND_UP(1000000000, rate);
>>>> +    rate = DIV_ROUND_UP(200, rate);
>>>> +    value = (u32)rate;
>>> Although it is unlikely, I think that we should check it is less
>>> than U32_MAX, return an error if it is not.
>> rate = DIV_ROUNC_UP(200, rate) means
>>
>> rate = (200 + rate -1)/rate
>>
>> and can not be more than 200 in any case (if rate =1).
>> So no need of the error check.
> OK, yes you are right. In that case there is no need to cast and so I
> would leave this code as-is and not change the type.
>

You mean keep value as unsigned long for value?

I think we can still say value as u32 and simply write
value = rate


Just remove the casting.