linux-kernel - Re: [PATCH] staging: fbtft: Replace mdelay() with msleep() and usleep

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Message-ID: <6ed64d7e-2899-ac18-78ed-508d14abf845@gmail.com>
Date:   Fri, 27 Jul 2018 19:43:28 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] staging: fbtft: Replace mdelay() with msleep() and
 usleep_range()



On 2018/7/27 18:34, Andy Shevchenko wrote:
> On Fri, Jul 27, 2018 at 12:21 PM, Jia-Ju Bai <baijiaju1990@...il.com> wrote:
>> reset() and init_display() are never called in atomic context.
>> They call mdelay() to busily wait, which is not necessary.
>> mdelay() can be replaced with msleep().
>>          gpio_set_value(par->gpio.reset, 0);
>>          udelay(20);
>>          gpio_set_value(par->gpio.reset, 1);
>> -       mdelay(120);
>> +       msleep(120);
> I didn't look to the rest, but this one will be inconsistent after your patch.
>
> The question here is why udelay() is needed, while mdelay() changed?
>

I thought udelay() is used for short delay, so it is not very necessary 
to change udelay() to usleep_range().
mdelay() is used for longer delay, so I changed it to msleep().

If you think udelay() should be also changed, I can send a new patch :)


Best wishes,
Jia-Ju Bai