linux-kernel - Re: [PATCH RFT/RFC v2 28/47] staging: media: zoran: convert mdelay to udelay

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Date:   Thu, 1 Oct 2020 09:54:35 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Corentin Labbe <clabbe@...libre.com>
Cc:     gregkh@...uxfoundation.org, hverkuil@...all.nl,
        laurent.pinchart@...asonboard.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH RFT/RFC v2 28/47] staging: media: zoran: convert mdelay
 to udelay

Em Fri, 25 Sep 2020 18:30:38 +0000
Corentin Labbe <clabbe@...libre.com> escreveu:

> As asked by checkpath, let's use udelay.
> 
> Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> ---
>  drivers/staging/media/zoran/zoran_device.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/zoran/zoran_device.c b/drivers/staging/media/zoran/zoran_device.c
> index 0ecb044f8e8f..4c9f6eafd130 100644
> --- a/drivers/staging/media/zoran/zoran_device.c
> +++ b/drivers/staging/media/zoran/zoran_device.c
> @@ -1332,9 +1332,9 @@ void zoran_init_hardware(struct zoran *zr)
>  void zr36057_restart(struct zoran *zr)
>  {
>  	btwrite(0, ZR36057_SPGPPCR);
> -	mdelay(1);
> +	udelay(1000);
>  	btor(ZR36057_SPGPPCR_SoftReset, ZR36057_SPGPPCR);
> -	mdelay(1);
> +	udelay(1000);

Ok, this is still on staging, so I'm willing to accept it, but
why aren't you using usleep_range() instead?

mdelay/udelay should be used only when the delay time should
be as precise as possible, as what they do is to keep the CPU
busy during the wait time.

I doubt that this is the case here. So, I would use,
instead, something like:

	usleep_range(1000, 2000)

(assuming that 4ms is still a reasonable time for the soft
reset to happen).

>  
>  	/* assert P_Reset */
>  	btwrite(0, ZR36057_JPC);



Thanks,
Mauro