linux-kernel - Re: [PATCH] staging: fbtft: fb_watterott: fix usleep

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Date:   Sun, 1 Nov 2020 07:39:48 +0100
From:   Greg KH <greg@...ah.com>
To:     Hassan Shahbazi <hassan.shahbazi@...ia.fi>
Cc:     linus.walleij@...aro.org, devel@...verdev.osuosl.org,
        Hassan Shahbazi <hassan@...chat.com>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] staging: fbtft: fb_watterott: fix usleep_range is
 preferred over udelay

On Sun, Nov 01, 2020 at 02:20:10AM +0200, Hassan Shahbazi wrote:
> Fix the checkpath.pl issue on fb_watterott.c. write_vmem and
> write_vmem_8bit functions are within non-atomic context and can
> safely use usleep_range.
> see Documentation/timers/timers-howto.txt
> 
> Signed-off-by: Hassan Shahbazi <hassan@...chat.com>
> ---
>  drivers/staging/fbtft/fb_watterott.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/fbtft/fb_watterott.c b/drivers/staging/fbtft/fb_watterott.c
> index 76b25df376b8..afcc86a17995 100644
> --- a/drivers/staging/fbtft/fb_watterott.c
> +++ b/drivers/staging/fbtft/fb_watterott.c
> @@ -84,7 +84,7 @@ static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
>  			par->txbuf.buf, 10 + par->info->fix.line_length);
>  		if (ret < 0)
>  			return ret;
> -		udelay(300);
> +		usleep_range(300, 310);
>  	}
>  
>  	return 0;
> @@ -124,7 +124,7 @@ static int write_vmem_8bit(struct fbtft_par *par, size_t offset, size_t len)
>  			par->txbuf.buf, 10 + par->info->var.xres);
>  		if (ret < 0)
>  			return ret;
> -		udelay(700);
> +		usleep_range(700, 710);

How do you know that these ranges are ok?  Are you able to test these
changes with real hardware?

thanks,

greg k-h