linux-kernel - Re: [PATCH] staging: fbtft: replace udelay with usleep

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Date:   Sat, 9 Jul 2022 12:30:51 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christos Kollintzas <c.kollintzas.92@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: fbtft: replace udelay with usleep_range

On Sat, Jul 09, 2022 at 01:06:56PM +0300, Christos Kollintzas wrote:
> Adhere to Linux kernel coding style.
> 
> Reported by checkpatch:
> 
> CHECK: usleep_range is preferred over udelay
> 
> Signed-off-by: Christos Kollintzas <c.kollintzas.92@...il.com>
> ---
>  drivers/staging/fbtft/fb_upd161704.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/fbtft/fb_upd161704.c b/drivers/staging/fbtft/fb_upd161704.c
> index c680160d6380..eeafbab4ace1 100644
> --- a/drivers/staging/fbtft/fb_upd161704.c
> +++ b/drivers/staging/fbtft/fb_upd161704.c
> @@ -32,27 +32,27 @@ static int init_display(struct fbtft_par *par)
>  
>  	/* oscillator start */
>  	write_reg(par, 0x003A, 0x0001);	/*Oscillator 0: stop, 1: operation */
> -	udelay(100);
> +	usleep_range(100, 110);

When doing these types of changes, you really need access to the
hardware involved in order to be able to properly test it.

Especially for this type of function which is trying to do timing
changes which the hardware requires.

Did you test this on the real hardware and did it work properly?

thanks,

greg k-h